The words you are searching are inside this book. To get more targeted content, please make full-text search by clicking here.

Sensation and Perception Unit IV 150c Unit Resources Module 16 STUDENT ACTIVITIES: † Fact or Falsehood? † The Stroop Eff ect Online † Understanding Weber’s Law

Discover the best professional documents and content resources in AnyFlip Document Base.
Search
Published by , 2016-09-26 02:45:04

Unit IV - Keansburg School District / Home

Sensation and Perception Unit IV 150c Unit Resources Module 16 STUDENT ACTIVITIES: † Fact or Falsehood? † The Stroop Eff ect Online † Understanding Weber’s Law

Unit IV

Sensation and Perception

PD Unit Overview • Discuss basic sensory concepts, such as thresholds and adaption.
• Appreciate how expectations, contexts, emotions, and motivation
We rely on our senses to understand the world around us. The sense
organs—the eyes, ears, nose, tongue, and skin—receive signals from influence perceptions.
the environment (sensation) and transfer those signals to the brain,
which processes the signals so we can understand them (percep- • Evaluate claims of ESP and the conclusions drawn from research
tion). In this unit, we look first at the processes of sensation, the ways
in which the sense organs receive signals from the environment. The on those claims.
eyes receive light waves. The ears receive sound waves. The nose and
tongue receive chemical signals, and the skin receives signals related • Explain how the eyes receive, process, and transform light signals.
to pressure, warmth, body position, and pain. Next, perception is ex- • Differentiate among the theories that explain our sensation and
amined. The brain processes and organizes these signals in interest-
ing ways. Most of the time, our perceptions reflect the reality of the perception of color.
world around us. Sometimes, though, our own expectations and the
brain’s desire to organize cause our perceptions to differ from reality • Describe gestalt perceptual principles, including figure–ground
and allow illusions to fool us. By studying how we sense and perceive
the world, we can understand more about ourselves and the world and grouping principles.
around us.
• Differentiate among the binocular and monocular depth cues that
This unit will help students appreciate how sensation and percep-
tion interact to influence our thoughts and behaviors. The integrated help us perceive 3D and motion.
processes of sensation and perception are the most basic ways we in-
teract with the world. By studying this unit, students will be able to: • Understand how perceptual constancies help us create meaning

• Differentiate between sensation and perception, understanding from sensory signals.

that these processes are interrelated. • Describe research on restored vision, sensory restriction, and

• Understand how much information can be processed at any given perceptual adaptation and how it contributes our understanding
of perception.
point in time.
• Explain how the ears process sound waves, contributing to our

perception of pitch and sound location.

• Describe how the senses of touch, pain, taste, smell, and body

position and movement work.

• Explain how the senses interact.

Alignment to AP® Course Description

Topic 4: Sensation and Perception (6–8% of AP® Examination)

Module Topic Essential Questions
Module 16 Selective Attention
• What are the implications of having the ability to attend selectively
Transduction
to stimuli?
Thresholds
• What are the implications of sensory information not getting
Sensory Adaptation
transformed and delivered to the brain properly?

• Why are thresholds important to our ability to interact with the world

around us?

• How does sensory adaptation help people live day-to-day?

Sensation and Perception Unit IV 150a

MyersPsyAP_TE_2e_U04.indd 1 2/26/14 9:34 AM

Module Topic Essential Questions
Module 17 Perceptual Set
Context Effects • What are some benefits and drawbacks of perceptual set?
Emotion and Motivation
• How influential is context on our sensation and perception?
Module 18 The Stimulus Input: Light Energy
• What are the implications of emotions and motivation influencing
The Eye
sensation and perception?
Visual Information Processing
• How is light important to vision?
Module 19 Color Vision • What are the most important aspects of light that make vision possible?
Visual Organization
• What are the most important aspects of the eye that make
Visual Interpretation
Module 20 The Stimulus Input: Sound Waves vision possible?

Module 21 The Ear • How do feature detectors and parallel processing affect our
Touch
Pain visual perception?
Taste
Smell • How do we see color?
Body Position and Movement
• Why do we organize visual information in particular ways?
Sensory Interaction • How does this type of organization help us understand the world

around us?

• How does losing or regaining vision affect perception?
• How does perceptual adaptation help us day-to-day?

• How are sound waves important to hearing?
• What are the most important aspects of sound waves that make

hearing possible?

• What aspects of the ear make hearing possible?

• Is touch a sensory system that is taken for granted?

• What is the importance of pain in our lives?

• How does our sense of taste affect other aspects of our lives?

• What is the importance of smell in daily life?

• How can knowing about our body position and movement

be important?

• Why is sensory interaction important?

150b Unit IV Sensation and Perception

MyersPsyAP_TE_2e_U04.indd 2 2/26/14 9:34 AM

Unit Resources Module 19

Module 16 STUDENT ACTIVITIES
• Fact or Falsehood?
STUDENT ACTIVITIES: • Binocular Vision vs. Monocular Vision
• Fact or Falsehood? • Autostereograms
• The Stroop Effect Online • Perceived Lunar Size
• Understanding Weber’s Law • The Ganzfeld
• Displacement Goggles
FLIP IT VIDEOS
• Top-Down and Bottom-Up Processing FLIP IT VIDEOS
• Signal Detection Theory • Gestalt Psychology
• Monocular Cues
Module 17
Module 20
TEACHER DEMONSTRATIONS
• Testing for ESP STUDENT ACTIVITY
• ESP Trick—Precognition (Playing Card Trick) • Fact or Falsehood?
• ESP Trick—Precognition (Newspaper Article Trick)
• ESP Trick—Clairvoyance FLIP IT VIDEO
• ESP Trick—Mental Telepathy (Gray Elephant in Denmark Trick) • Theories of Hearing
• ESP Trick—Mental Telepathy (Telephone Book Trick)
Module 21
STUDENT ACTIVITIES
• Fact or Falsehood? TEACHER DEMONSTRATIONS
• Belief in ESP Scale • Vision and Taste

Module 18 STUDENT ACTIVITIES
• Fact or Falsehood?
TEACHER DEMONSTRATION • Warm Plus Cold Equals Hot
• Movement Aftereffects • Tasting Salt and Sugar

STUDENT ACTIVITIES: FLIP IT VIDEO
• Fact or Falsehood? • Theories of Pain
• Locating the Retinal Blood Vessels
• Subjective Colors
• The Color Vision Screening Inventory and Color Blindness

FLIP IT VIDEOS
• Rods and Cones in the Retina
• Feature Detectors

Sensation and Perception Unit IV 150c

MyersPsyAP_TE_2e_U04.indd 3 2/26/14 9:34 AM

Unit IV

Sensation and Perception

Modules

16 Basic Principles of Sensation and Perception
17 Influences on Perception
18 Vision
19 Visual Organization and Interpretation
20 Hearing
21 The Other Senses

I“ have perfect vision,” explains my colleague, Heather Sellers, an acclaimed writer
and teacher. Her vision may be fine, but there is a problem with her perception.
She cannot recognize faces.
In her memoir, You Don’t Look Like Anyone I Know, Sellers (2010) tells of awkward
moments resulting from her lifelong prosopagnosia—face blindness.

In college, on a date at the Spaghetti Station, I returned from the bathroom and
plunked myself down in the wrong booth, facing the wrong man. I remained un-
aware he was not my date even as my date (a stranger to me) accosted Wrong Booth
Guy, and then stormed out of the Station. I can’t distinguish actors in movies and on
television. I do not recognize myself in photos or videos. I can’t recognize my step-
sons in the soccer pick-up line; I failed to determine which husband was mine at a
party, in the mall, at the market.

Her inability to recognize faces means that people sometimes perceive her as
snobby or aloof. “Why did you walk past me?” a neighbor might later ask. Similar
to those of us with hearing loss who fake hearing during trite social conversation,
Sellers sometimes fakes recognition. She often smiles at people she passes, in case
she knows them. Or she pretends to know the person with whom she is talking.
(To avoid the stress associated with such perception failures, people with serious
hearing loss or with prosopagnosia often shy away from busy social situations.) But

150

Pacing Guide

Module Topic Standard Schedule Days Block Schedule Days 1/21/14 9:32 AM
Module 16 1
Selective Attention MyersAP_SE_2e_Mod16_B.indd 150
Module 17 Transduction 1.5
Module 18 Thresholds 1 1
Sensory Adaptation
Module 19
Module 20 Perceptual Set
Module 21 Context Effects
Emotion and Motivation

The Stimulus Input: Light Energy 1
The Eye 1
Visual Information Processing

Color Vision

Visual Organization
Visual Interpretation

The Stimulus Input: Sound Waves 1
The Ear

Touch 1
Pain
Taste
Smell
Body Position and Movement
Sensory Interaction

150 Unit IV Sensation and Perception

MyersPsyAP_TE_2e_U04.indd 150 2/26/14 9:34 AM

Basic Principles of Sensation and Perception Module 16 151

there is an upside: When encountering someone who previously irritated her, she TEACH
typically won’t feel ill will, because she doesn’t recognize the person. TRM Discussion Starter

Unlike Sellers, most of us have (as Module 18 explains) a functioning area on the Use the Module 16 Fact or Falsehood?
underside of our brain’s right hemisphere that helps us recognize a familiar human student activity from the TRM to intro-
face as soon as we detect it—in only one-seventh of a second (Jacques & Rossion, duce the concepts from this module.
2006). This ability illustrates a broader principle. Nature’s sensory gifts enable each
animal to obtain essential information. Some examples: TEACH
Teaching Tip
• Frogs, which feed on flying insects, have cells in their eyes that fire only in
response to small, dark, moving objects. A frog could starve to death knee- This unit provides numerous oppor-
deep in motionless flies. But let one zoom by and the frog’s “bug detector” tunities for active learning. Don’t be
cells snap awake. afraid to use your time to do the activi-
ties suggested in the text and from
• Male silkworm moths’odor receptors can detect one-billionth of an ounce the accompanying Teacher’s Resource
of sex attractant per second released by a female one mile away. That is why Materials. Students will understand the
silkworms continue to be. information better if they are able to
experience the material firsthand.
• Human ears are most sensitive to sound frequencies that include human
voices, especially a baby’s cry. ENGAGE

In this unit, we’ll look more closely at what psychologists have learned about Online Activities
how we sense and perceive the world around us.
Use any or all of the following sites to
Module 16 help prepare for this unit or to give to
students to explore:
Basic Principles of Sensation Beau Lark/Corbis ᭹ Hugh Foley’s Sensation and
and Perception
Perception page at www.skidmore.
Module Learning Objectives edu/~hfoley/perception.htm.
᭹ Psychology Tutorials at http://psych.
16-1 Contrast sensation and perception, and explain the difference hanover.edu/Krantz/tutor.html.
between bottom-up and top-down processing. ᭹ The Internet Psychology Lab (IPL) at
www.ipsych.com.
16-2 Discuss how much information we can consciously attend to at once. ᭹ Interactive Eye at www.nei.nih.gov/
health/eyediagram.
16-3 Identify the three steps that are basic to all our sensory systems.

16-4 Distinguish between absolute and difference thresholds, and discuss
whether we can sense and be affected by stimuli below the absolute
threshold.

16-5 Explain the function of sensory adaptation.

E N G AG EMyersAP_SE_2e_Mod16_B.indd 151 1/21/14 9:32 AM

Online Activities

The Online Psychology Laboratory (OPL) is an
excellent website that has online experiments
in all areas of psychology, especially sensation
and perception, that students can participate
in and download results to analyze. Using
a computer lab, students can participate in
several different experiments or ones that you
choose by accessing http://opl.apa.org.

Basic Principles of Sensation and Perception Module 16 151

MyersPsyAP_TE_2e_U04.indd 151 2/20/14 8:09 AM

152 U n i t I V Sensation and Perception

TEACH sensation the process by which 16-1 What are sensation and perception? What do we mean by bottom-up
our sensory receptors and nervous processing and top-down processing?
Flip It system receive and represent
stimulus energies from our Sellers’curious mix of “perfect vision” and face blindness illustrates the distinction between
Help your students understand top- environment. sensation and perception. When she looks at a friend, her sensation is normal: Her senses
down and bottom-up processing perception the process of detect the same information yours would, and they transmit that information to her brain.
better by assigning the Flip It Video: organizing and interpreting And her perception—the processes by which her brain organizes and interprets sensory
Top-Down and Bottom-Up Processing. sensory information, enabling us to input—is almost normal. Thus, she may recognize people from their hair, gait, voice, or par-
recognize meaningful objects and ticular physique, just not their face. Her experience is much like the struggle you or I would
TEACH events. have trying to recognize a specific penguin in a group of waddling penguins.
bottom-up processing analysis
Concept Connections that begins with the sensory In our everyday experiences, sensation and perception blend into one continuous pro-
receptors and works up to the cess. In this module, we slow down that process to study its parts, but in real life, our sensory
Students may more readily identify brain’s integration of sensory and perceptual processes work together to help us decipher the world around us.
top-down processing with stereotyp- information.
ing because both use previous expec- top-down processing • Our bottom-up processing starts at the sensory receptors and works up to higher
tations to make judgments about the information processing guided by levels of processing.
world around us. Help students under- higher-level mental processes, as
stand that although stereotyping can when we construct perceptions • Our top-down processing constructs perceptions from the sensory input by
be negative, it can also be very efficient drawing on our experience and drawing on our experience and expectations.
for people as they interact with certain expectations.
stimuli. Without top-down processing, selective attention the focusing As our brain absorbs the information in FIGURE 16.1, bottom-up processing enables
we would have to interpret the world of conscious awareness on a our sensory systems to detect the lines, angles, and colors that form the flower and leaves.
as if it were constantly new. It would particular stimulus. Using top-down processing we interpret what our senses detect.
be like having to relearn how to add in
math class every single day! Figure 16.1 But how do we do it? How do we create meaning from the blizzard of sensory stimuli
What’s going on here? Our bombarding our bodies 24 hours a day? Meanwhile, in a silent, cushioned, inner world, our
TEACH sensory and perceptual processes brain floats in utter darkness. By itself, it sees nothing. It hears nothing. It feels nothing. So,
work together to help us sort out how does the world out there get in? To phrase the question scientifically: How do we construct
Common Pitfalls the complex images, including the our representations of the external world? How do a campfire’s flicker, crackle, and smoky
hidden couple in Sandro Del-Prete’s scent activate neural connections? And how, from this living neurochemistry, do we cre-
Students may get bottom-up and drawing, The Flowering of Love. ate our conscious experience of the fire’s motion and temperature, its aroma and beauty?
top-down processing confused. In search of answers to such questions, let’s look at some processes that cut across all our
Help students remember the differ- sensory systems. To begin, where is the border between our conscious and unconscious
ence between the 2 concepts with awareness, and what stimuli cross that threshold?
these tips:
Sandro Del-Prete Selective Attention
᭹ Bottom-up processing—we process
this way when we have no prior 16-2 How much information do we consciously attend to at once?
knowledge. We start at the bottom
and work our way up. Through selective attention, your awareness focuses, like a flashlight beam, on a minute
aspect of all that you experience. By one estimate, your five senses take in 11,000,000 bits
᭹ Top-down processing—we process of information per second, of which you consciously process about 40 (Wilson, 2002). Yet
this way when we have prior your mind’s unconscious track intuitively makes great use of the other 10,999,960 bits. Until
knowledge. We start at the top and reading this sentence, for example, you have been unaware that your shoes are pressing
work to process details. against your feet or that your nose is in your line of vision. Now, suddenly, your attentional
spotlight shifts. Your feet feel encased, your nose stubbornly intrudes on the words before
you. While focusing on these words, you’ve also been blocking other parts of your environ-
ment from awareness, though your peripheral vision would let you see them easily.You can
change that. As you stare at the X below, notice what surrounds these sentences (the edges
of the page, the desktop, the floor).

X

A classic example of selective attention is the cocktail party effect—your ability to attend
to only one voice among many (while also being able to detect your own name in an unat-
tended voice). This effect might have prevented an embarrassing and dangerous situation in

E N G AG EMyersAP_SE_2e_Mod16_B.indd 152 1/21/14 9:32 AM MyersAP_SE_2e

Online Activities

Use this series of photos from the Tai-Wiki-
Widbee blog to see if students notice glaring
incongruities from a Colgate® dental floss
ad campaign: http://tywkiwdbi.blogspot.
com/2013/01/what-do-you-notice-about-
these-photos.html.

152 Unit IV Sensation and Perception 2/20/14 8:09 AM

MyersPsyAP_TE_2e_U04.indd 152

Basic Principles of Sensation and Perception Module 16 153

2009, when two commercial airline pilots “lost track of time.” Focused on their laptops and “Has a generation of texters, ENGAGE
conversation, they ignored alarmed air traffic controllers’ attempts to reach them as they surfers, and twitterers evolved the
overflew their Minneapolis destination by 150 miles. If only the controllers had known and enviable ability to process multiple Enrichment
spoken the pilots’ names. streams of novel information
in parallel? Most cognitive People with ADHD (attention-deficit/
Selective Attention and Accidents psychologists doubt it.” -STEVEN hyperactivity disorder) seem to lack
PINKER, “NOT AT ALL,” 2010 the ability to be selectively attentive.
Text or talk on the phone while driving, or attend to a music player or GPS, and your selec- Instead of filtering out unimportant
AP® Exam Tip stimuli in order to focus on important
tive attention will shift back and forth between the road and its electronic competition. But ones, they attend to all stimuli in the
You may wish to think about environment, making it difficult, if not
when a demanding situation requires it, you’ll probably give the road your full attention. how the information on selective impossible, to process information
attention relates to something a correctly.
You’ll probably also blink less. When focused on a task, such as reading, people blink less little less dangerous: studying.
The same principles apply. The TEACH
than when their mind is wandering (Smilek et al., 2010). If you want to know whether your more time you spend texting,
tweeting, and Facebooking, the TRM Teaching Tip
dinner companion is focused on what you’re saying, watch for eyeblinks and hope there less focused you’ll be on the
material you’re trying to master. Apply selective attention to students’
won’t be too many. A better strategy is to spend 25 lives by having them share experiences
minutes doing schoolwork and where they were either so caught up in
We pay a toll for switching attentional gears, especially when we shift to complex tasks, like schoolwork alone. Then you an activity that they missed something
can reward yourself with a few obvious in the environment, or when
noticing and avoiding cars around us. The toll is a slight and sometimes fatal delay in coping minutes of social networking. the environment was so distract-
ing that they couldn’t concentrate.
(Rubenstein et al., 2001). About 28 percent of traffic accidents occur when people are chatting Students with attention difficulties
may be reassured to know that others
on cell phones or texting (National Safety Council, 2010). One study tracked long-haul truck are frequently unable to concentrate
or that they, too, have times when
drivers for 18 months. The video cameras mounted in their cabs showed they were at 23 times their own intense concentration makes
them miss things. Use Student Activity:
greater risk of a collision while texting (VTTI, 2009). Mindful of such findings, the United States The Stroop Effect Online from the TRM
to show the difficulty with attending to
in 2010 banned truckers and bus drivers from texting while driving (Halsey, 2010). multiple stimuli at once.

It’s not just truck drivers who are at risk. One in four teen drivers with cell phones

admit to texting while driving (Pew, 2009). Multitasking comes at a cost: fMRI scans offer a

biological account of how multitasking distracts from brain resources allocated to driving.

They show that brain activity in areas vital to driving decreases an average 37 percent when

a driver is attending to conversation (Just et al., 2008).

Even hands-free cell-phone talking is more distracting than a conversation with pas-

sengers, who can see the driving demands and pause the conversation. When University

of Sydney researchers analyzed phone re-

cords for the moments before a car crash,
Sally Forth
© The New Yorker Collection, 2009, Robert Leightonthey found that cell-phone users (even with
from cartoonbank.com. All Rights Reserved.
hands-free sets) were four times more at risk

(McEvoy et al., 2005, 2007). Having a passen-

ger increased risk only 1.6 times. This risk dif-

ference also appeared in an experiment that

asked drivers to pull off at a freeway rest stop

8 miles ahead. Of drivers conversing with a

passenger, 88 percent did so. Of those talk-

ing on a cell phone, 50 percent drove on by

(Strayer & Drews, 2007). “I wasn’t texting. I was building this ship in a bottle.”

SALLY FORTH

Driven to distraction
In driving-simulation
experiments, people whose
attention is diverted by cell-
phone conversation make
more driving errors.

1/21/14 9:32 AM E N G AG EMyersAP_SE_2e_Mod16_B.indd 153 ENGAGE 1/22/14 8:01 AM

Enrichment Active Learning

When people get so caught up in an experi- Have students conduct research about laws
ence that they miss out on obvious stimuli in governing cell phone use and texting while
the environment, they are said to be having a driving. Have students see whether research
flow experience. Flow, a term coined by Mihalyi into attention was used to craft or justify the
Csikszentmihalyi (chik-sent-me-high), involves laws. Consider having your students develop
being skilled at a challenging task that takes a public relations campaign about distracted
away our sense of self-consciousness and driving that will use psychological principles to
awareness of time and the presence of others appeal to their peers. Students can also try the
around us. New York Times distracted driving simulation at
www.nytimes.com/interactive/2009/07/19/
technology/20090719-driving-game.
html?_r=0.

Basic Principles of Sensation and Perception Module 16 153

MyersPsyAP_TE_2e_U04.indd 153 2/20/14 8:09 AM

154 U n i t I V Sensation and Perception

TEACH inattentional blindness failing Most European countries and American states now ban hand-held cell phones while
to see visible objects when our driving (Rosenthal, 2009). Engineers are also devising ways to monitor drivers’ gaze and to
Teaching Tip attention is directed elsewhere. direct their attention back to the road (Lee, 2009).

Have students speculate how selective change blindness failing to Selective Inattention
attention is related to the evolutionary notice changes in the environment.
perspective. They can give examples of At the level of conscious awareness, we are “blind” to all but a tiny sliver of visual stimuli.
each of the following: Researchers demonstrated this inattentional blindness dramatically by showing people
a 1-minute video in which images of three black-shirted men tossing a basketball were
᭹ If we had to attend to every superimposed over the images of three white-shirted players (Neisser, 1979; Becklen &
stimulus in the environment, we Cervone, 1983). The viewers’ supposed task was to press a key every time a black-shirted
might be hindered from action. player passed the ball. Most focused their attention so completely on the game that they
failed to notice a young woman carrying an umbrella saunter across the screen midway
᭹ However, if we miss important through the video (FIGURE 16.2). Seeing a replay of the video, viewers were astonished to
stimuli in the environment due see her (Mack & Rock, 2000). This inattentional blindness is a by-product of what we are
to attention that is too selective, really good at: focusing attention on some part of our environment.
we may fall victim to all sorts of
trouble—falls, car accidents, etc. In a repeat of the experiment, smart-aleck researchers Daniel Simons and Christopher
Chabris (1999) sent a gorilla-suited assistant through the swirl of players. During its 5- to
ENGAGE 9-second cameo appearance, the gorilla paused to thump its chest. Still, half the conscientious
pass-counting viewers failed to see it. In another follow-up experiment, only 1 in 4 students
Online Activities engrossed in a cell-phone conversation while crossing a campus square noticed a clown-suited
unicyclist in their midst (Hyman et al., 2010). (Most of those not on the phone did notice.) At-
Students may be interested in learning tention is powerfully selective.Your conscious mind is in one place at a time.
more about change blindness by visit-
ing the website created by University of Given that most people miss someone in a gorilla or clown suit while their attention is
Illinois professor Daniel J. Simons, author riveted elsewhere, imagine the fun that magicians can have by manipulating our selective
of the book, The Invisible Gorilla. He and attention. Misdirect people’s attention and they will miss the hand slipping into the pocket.
his team research attention issues, and “Every time you perform a magic trick, you’re engaging in experimental psychology,” says
they have created several famous videos Teller, a magician and master of mind-messing methods (2009).
that demonstrate our blindness to
change. Visit www.simonslab.com. Magicians also exploit a form of inattentional blindness called change blindness. By
selectively riveting our attention on their left hand’s dramatic act, we fail to notice changes
made with their other hand. In laboratory experiments, viewers didn’t notice that, after a brief
visual interruption, a big Coke bottle had disappeared, a railing had risen, or clothing color
had changed (Chabris & Simons, 2010; Resnick et al., 1997). Focused on giving directions to
a construction worker, two out of three people also failed to notice when he was replaced by
another worker during a staged interruption (FIGURE 16.3). Out of sight, out of mind.

Figure 16.2 1/21/14 9:32 AM MyersAP_SE_2e
Testing selective attention In
this classic experiment, viewers who
were attending to basketball tosses
among the black-shirted players
usually failed to notice the umbrella-
toting woman sauntering across the
screen. (From Neisser, 1979.)

MyersAP_SE_2e_Mod16_B.indd 154

154 Unit IV Sensation and Perception 2/20/14 8:09 AM

MyersPsyAP_TE_2e_U04.indd 154

Basic Principles of Sensation and Perception Module 16 155

Figure 16.3 TEACH

Change blindness While Concept Connections
a man (white hair) provides
directions to a construction Relate choice blindness to implicit
worker, two experimenters rudely associations. Harvard researchers have
pass between them. During this been examining how our unconscious
interruption, the original worker associations affect prejudice and dis-
switches places with another crimination. Have students take
person wearing different-colored the implicit association test online:
clothing. Most people, focused https://implicit.harvard.edu/implicit.
on their direction giving, do not
notice the switch. ENGAGE

An equally astonishing form of inattention is choice blindness. At one Swedish super- Online Activities
market, people tasted two jams, indicated their preference, and then tasted again their pre-
ferred jam and explained their preference. Fooled by trick jars (see FIGURE 16.4) most Several versions of the change and
people didn’t notice that they were actually “retasting” their nonpreferred jam. choice blindness experiments are
available on social media sites such
Image is from the research paper by Lars Hall, as YouTube. You can find videos by
Petter Johansson, and colleagues (2010). searching for “change blindness
experiment” or “choice blindness
Some stimuli, however, are so powerful, so strikingly distinct, that we experience pop- Figure 16.4 experiment.” These videos may be
out, as when we notice an angry face in a crowd. We don’t choose to attend to these stimuli; Marketplace magic Prankster used as a classroom demonstration
they draw our eye and demand our attention. researchers Lars Hall, Petter of these phenomena or as videos for
Johansson, and colleagues (2010) students to watch on their own, which
Our selective attention extends even into our sleep, as we will see. invited people to sample two jams you can then use as a starting off point
and pick one to retaste. By flipping the for classroom discussion.
Transduction jars after putting the lids back on, the
researchers actually induced people
16-3 What three steps are basic to all our sensory systems? to “resample” their nonchosen jam.
Yet, even when asked whether they
Every second of every day, our sensory systems perform an amazing feat: They convert one noticed anything odd, most tasters
form of energy into another.Vision processes light energy. Hearing processes sound waves. were choice blind. Even when given
All our senses markedly different jams, they usually
failed to notice the switch.
• receive sensory stimulation, often using specialized receptor cells.
• transform that stimulation into neural impulses. transduction conversion of one
• deliver the neural information to our brain. form of energy into another. In
sensation, the transforming of
The process of converting one form of energy into another that your brain can use is stimulus energies, such as sights,
called transduction. Later in this unit, we’ll focus on individual sensory systems. How do sounds, and smells, into neural
we see? Hear? Feel pain? Taste? Smell? Keep our balance? In each case, we’ll consider these impulses our brain can interpret.
three steps—receiving, transforming, and delivering the information to the brain. We’ll also
see what psychophysics has discovered about the physical energy we can detect and its psychophysics the study
effects on our psychological experiences. of relationships between the
physical characteristics of stimuli,
First, though, let’s explore some strengths and weaknesses in our ability to detect and such as their intensity, and our
interpret stimuli in the vast sea of energy around us. psychological experience of them.

1/21/14 9:32 AM MyersAP_SE_2e_Mod16_B.indd 155 1/21/14 9:32 AM

Basic Principles of Sensation and Perception Module 16 155

MyersPsyAP_TE_2e_U04.indd 155 2/20/14 8:09 AM

156 U n i t I V Sensation and Perception

ENGAGE Thresholds

Enrichment 16-4 What are the absolute and difference thresholds, and do stimuli
below the absolute threshold have any influence on us?
As long ago as 1888, Joseph Jastrow
speculated that lapses of attention, absolute threshold the At this moment, you and I are being struck by X-rays and radio waves, ultraviolet and infra-
slight fatigue, and other psychological minimum stimulation needed to red light, and sound waves of very high and very low frequencies. To all of these we are blind
changes could cause fluctuations in detect a particular stimulus 50 and deaf. Other animals with differing needs detect a world that lies beyond our experience.
the absolute threshold. percent of the time. Migrating birds stay on course aided by an internal magnetic compass. Bats and dolphins
locate prey using sonar, bouncing echoing sound off objects. Bees navigate on cloudy days
ENGAGE signal detection theory a theory by detecting invisible (to us) polarized light.
predicting how and when we detect
Enrichment the presence of a faint stimulus The shades on our own senses are open just a crack, allowing us a restricted awareness
(signal) amid background stimulation of this vast sea of energy. But for our needs, this is enough.
Gustav Fechner (1801–1887) devel- (noise). Assumes that there is no
oped 3 methods of experimental single absolute threshold and that Absolute Thresholds
measurement used to study sensory detection depends partly on a
phenomenon: person’s experience, expectations, To some kinds of stimuli we are exquisitely sensitive. Standing atop a mountain on an ut-
᭹ Method of limits. Begin with a motivation, and alertness. terly dark, clear night, most of us could see a candle flame atop another mountain 30 miles
away. We could feel the wing of a bee falling on our cheek. We could smell a single drop of
minimal stimulus and increase it Try This perfume in a three-room apartment (Galanter, 1962).
until the participant can perceive
it. This method helps determine Try out this old riddle on a couple of German scientist and philosopher Gustav Fechner (1801–1887) studied our awareness
the “just noticeable difference.” friends. “You’re driving a bus with of these faint stimuli and called them our absolute thresholds—the minimum stimula-
᭹ Method of right and wrong 12 passengers. At your first stop, 6 tion necessary to detect a particular light, sound, pressure, taste, or odor 50 percent of the
cases. Present identical stimuli passengers get off. At the second time. To test your absolute threshold for sounds, a hearing specialist would expose each of
repeatedly—either single stop, 3 get off. At the third stop, 2 your ears to varying sound levels. For each tone, the test would define where half the time
stimuli at the threshold or pairs more get off but 3 new people get you could detect the sound and half the time you could not. That 50-50 point would define
of stimuli that are very similar. on. What color are the bus driver’s your absolute threshold.
The participant responds yes if eyes?” Do your friends detect the
perceived or if a difference exists, signal—who is the bus driver?— Detecting a weak stimulus, or signal, depends not only on the signal’s strength (such as
or no if not perceived or different. amid the accompanying noise? a hearing-test tone) but also on our psychological state—our experience, expectations, mo-
᭹ Method of adjustment. Adjust tivation, and alertness. Signal detection theory predicts when we will detect weak signals
a comparison stimulus until it (measured as our ratio of “hits” to “false alarms”) (FIGURE 16.5). Signal detection theorists
appears identical to the standard seek to understand why people respond differently to the same stimuli (have you ever noticed
stimulus. Every error is recorded that some teachers are much more likely than others to detect students texting during class?)
and after many trials, the average and why the same person’s reactions vary as circumstances change. Exhausted parents will
error is computed. It, too, provides notice the faintest whimper from a newborn’s cradle while failing to notice louder, unimport-
a measure of just noticeable ant sounds. Lonely, anxious people at speed-dating events also respond with a low threshold
difference. and thus tend to be unselective in reaching out to potential dates (McClure et al., 2010).

TEACH © Inspirestock/Corbis

Flip It Figure 16.5

Students can get additional help Signal detection What three factors will
understanding signal detection theory make it more likely that you correctly detect a
by watching the Flip It Video: Signal text message?
Detection Theory on this topic.
ANSWER: (1) You are expecting a text
TEACH message. (2) It is important that you see the
text message and respond. (3) You are alert.
Common Pitfalls
E N G AG EMyersAP_SE_2e_Mod16_B.indd 156 1/21/14 9:32 AM MyersAP_SE_2e
Students may wonder why anyone
cares about signal detection theory. Active Learning forward to reach threshold. At other times the
The research in this area is especially sound will get louder and they will be able to
important to fields where attention to Have students place an alarm clock (or step back. This changing sensitivity indicates
detail amid environmental distractions wristwatch) on a table in a quiet room. They that the “absolute threshold” is anything
is paramount, such as air traffic control- should move away so that they can no longer but absolute.
lers, security screeners, law enforce- hear the ticking, then gradually move toward
ment, and even ordinary car drivers. the clock until they begin to hear the sound. Coren, S., Ward, L. M., & Enns, J. T. (1999). Sensation
This is the “momentary” threshold. If they and perception (5th ed.). Fort Worth, TX: Harcourt
remain in place, occasionally they won’t be Brace.
able to hear the sound and will need to step

156 Unit IV Sensation and Perception

MyersPsyAP_TE_2e_U04.indd 156 2/20/14 8:09 AM

Basic Principles of Sensation and Perception Module 16 157

AJ Photo/Science Source Percentage 100 Figure 16.6 ENGAGE
of correct
detections Absolute threshold Can I Active Learning
75 detect this sound? An absolute
threshold is the intensity at which With federal takeover of airport screen-
50 a person can detect a stimulus ing as a result of the 9/11 attacks,
half the time. Hearing tests locate accurate signal detection (like looking
25 these thresholds for various for suspicious bags, packages, or activi-
frequency levels. Stimuli below ties by passengers) by Transportation
your absolute threshold are Safety Administration (TSA) employees
subliminal. remains an important concern. Contact
a nearby TSA office or air traffic control
Subliminal office to ask if representatives from
stimuli your class might interview a supervi-
sor about the following issues in signal
0 Absolute Medium detection:
Low threshold
᭹ What policies are in place that
Intensity of stimulus increase accurate signal detection?

Stimuli you cannot detect 50 percent of the time are subliminal—below your absolute subliminal below one’s absolute ᭹ What training programs do you use
threshold (FIGURE 16.6). Under certain conditions, you can be affected by stimuli so weak threshold for conscious awareness. to equip screeners to make accurate
that you don’t consciously notice them. An unnoticed image or word can reach your visual priming the activation, often calls about stimuli?
cortex and briefly prime your response to a later question. In a typical experiment, the im- unconsciously, of certain
age or word is quickly flashed, then replaced by a masking stimulus that interrupts the brain’s associations, thus predisposing ᭹ Do you offer incentives based on
processing before conscious perception (Van den Bussche et al., 2009). For example, one ex- one’s perception, memory, or accurate performance? Why or
periment subliminally flashed either emotionally positive scenes (kittens, a romantic couple) response. why not?
or negative scenes (a werewolf, a dead body) an instant before participants viewed slides of
people (Krosnick et al., 1992). The participants consciously perceived either scene as only a “The heart has its reasons which ᭹ Does your office engage in periodic
flash of light.Yet the people somehow looked nicer if their image immediately followed un- reason does not know.” -PASCAL, checks of accurate signal detection?
perceived kittens rather than an unperceived werewolf. As other experiments confirm, we can PENSÉES, 1670 What methods do you use to study
evaluate a stimulus even when we are not aware of it—and even when we are unaware of our this area?
evaluation (Ferguson & Zayas, 2009).

How do we feel or respond to what we do not know and cannot describe? An imper-
ceptibly brief stimulus often triggers a weak response that can be detected by brain scanning
(Blankenburg et al., 2003; Haynes & Rees, 2005, 2006). Only when the stimulus triggers
synchronized activity in several brain areas does it reach consciousness (Dehaene, 2009).
Once again we see the dual-track mind at work: Much of our information processing occurs
automatically, out of sight, off the radar screen of our conscious mind.

So can we be controlled by subliminal messages? For more on that ques-
tion, see Thinking Critically About: Can Subliminal Messages Control Our
Behavior? on the next page.

Difference Thresholds

To function effectively, we need absolute thresholds low enough

to allow us to detect important sights, sounds, textures, tastes,

and smells. We also need to detect small differences among stim-

uli. A musician must detect minute discrepancies when tuning

an instrument. Students in the hallway must detect the sound

of their friends’voices amid all the other voices. Even after living

two years in Scotland, sheep baa’s all sound alike to my ears.

But not to those of ewes, which I have observed streaking, after

shearing, directly to the baa of their lamb amid the chorus of

other distressed lambs. Eric Isselée/Shutterstock

1/21/14 9:32 AM E N G AG EMyersAP_SE_2e_Mod16_B.indd 157 1/23/14 1:57 PM

Enrichment ᭹ Many of the popular articles fail to report Pratkanis, A. (1990, August). Subliminal
scientific evidence that is critical of claims for sorcery then and now: Who is seducing
Anthony Pratkanis identified factors that subliminal persuasion. whom? Paper presented at the 98th annual
contribute to the public’s beliefs regarding convention of the American Psychological
subliminal influence. ᭹ Belief in subliminal persuasion may serve Association, Boston, MA.
a need for many individuals. Subliminal
᭹ Popular accounts of subliminal influence persuasion takes on a supernatural “the
appeal to the “pop” psychology of the day. devil made me do it” quality capable of
explaining why Americans engage in
᭹ Popular accounts link subliminal influence irrational consumer behavior.
to the issue of the day. Subliminal influence
first emerged as a national concern after
the Korean War when brainwashing and
hypnotic suggestion captured the nation’s
imagination in films such as The Manchurian
Candidate.

Basic Principles of Sensation and Perception Module 16 157

MyersPsyAP_TE_2e_U04.indd 157 2/26/14 9:34 AM

158 U n i t I V Sensation and Perception

TEACH Thinking Critically About

Common Pitfalls Can Subliminal Messages Control Our Behavior?

Some students may have heard that Hoping to penetrate our unconscious, entrepreneurs offer au- Babs Reingold for Worth Publishers Subliminal
movie theatres in the 1950s used sub- dio and video programs to help us lose weight, stop smoking, persuasion?
liminal advertising to increase sales of or improve our memories. Soothing ocean sounds may mask Although subliminally
popcorn and soda. They placed frames messages we cannot consciously hear: “I am thin”; “Smoke presented stimuli can
that said, “buy popcorn” and “buy tastes bad”; or “I do well on tests—I have total recall of infor- subtly influence people,
Coke” within movies, which was sup- mation.” Such claims make two assumptions: (1) We can un- experiments discount
posed to encourage people to sublimi- consciously sense subliminal (literally, “below threshold”) stimuli. attempts at subliminal
nally want to purchase concessions. (2) Without our awareness, these stimuli have extraordinary advertising and self-
This advertising ploy never happened. suggestive powers. Can we? Do they? improvement. (The
The source of the myth, James Vicary, playful message here is
actually lied about experiments he As we have seen, subliminal sensation is a fact. Remember not actually subliminal—
conducted at a New Jersey movie the- that an “absolute” threshold is merely the point at which we can because you can easily
atre. His lie, however, led the Federal detect a stimulus half the time. At or slightly below this thresh- perceive it.)
Communications Commission to ban old, we will still detect the stimulus some of the time.
so-called “subliminal advertising” in revealed no effects. Yet the students perceived themselves re-
1974 (Source: www.snopes.com). But does this mean that claims of subliminal persuasion ceiving the benefits they expected. Those who thought they
are also facts? The near-consensus among researchers is No. had heard a memory recording believed their memories had
TEACH The laboratory research reveals a subtle, fleeting effect. Priming improved. Those who thought they had heard a self-esteem
thirsty people with the subliminal word thirst might therefore, for recording believed their self-esteem had grown. (Reading this
Concept Connections a moment, make a thirst-quenching beverage ad more persua- research, one hears echoes of the testimonies that ooze from
sive (Strahan et al., 2002). Likewise, priming thirsty people with ads for such products. Some customers, having bought what
Although subliminal advertising may Lipton Iced Tea may increase their choosing the primed brand is not supposed to be heard [and having indeed not heard it!]
not work, priming does. If we are (Karremans et al., 2006; Veltkamp et al., 2011; Verwijmeren offer testimonials like, “I really know that your recordings were
exposed to stimuli about a specific et al., 2011a,b). But the subliminal-message hucksters claim invaluable in reprogramming my mind.”)
subject, we are more likely to recog- something different: a powerful, enduring effect on behavior.
nize information about that subject in Over a decade, Greenwald conducted 16 double-blind ex-
the environment. This phenomenon To test whether subliminal recordings have this enduring ef- periments evaluating subliminal self-help recordings. His results
is related to context effects, which is fect, researchers randomly assigned university students to lis- were uniform: Not one of the recordings helped more than a
discussed in more detail in Module 17. ten daily for 5 weeks to commercial subliminal messages claim- placebo (Greenwald, 1992). And placebos, you may remember,
ing to improve either self-esteem or memory (Greenwald et al., work only because we believe they will work.
ENGAGE 1991, 1992). But the researchers played a practical joke and
switched half the labels. Some students who thought they were
TRM Active Learning receiving affirmations of self-esteem were actually hearing the
memory-enhancement message. Others got the self-esteem
Weber’s law can be applied to many message but thought their memory was being recharged.
situations. Robert Cialdini suggests
having students imagine a man who Were the recordings effective? Students’ test scores for
wants to buy a 3-piece suit and a self-esteem and memory, taken before and after the 5 weeks,
sweater. If you were the salesperson,
which should you show him first in The difference The difference threshold (or the just noticeable
order to get him to spend the most threshold In this difference [jnd]) is the minimum difference a person
money? You might think it best to sell computer-generated copy can detect between any two stimuli half the time.
the sweater first. Having spent a lot on of the Twenty-third Psalm, That difference threshold increases with the size of
a suit, the customer might be reluctant each line of the typeface the stimulus. Thus, if you add 1 ounce to a 10-ounce
to spend more on a sweater. However, increases slightly. How weight, you will detect the difference; add 1 ounce to a
sales motivation analysts suggest the many lines are required for 100-ounce weight and you probably will not.
opposite. Sell the suit first because the you to experience a just
additional cost of the sweater will not noticeable difference? In the nineteenth century, Ernst Weber noted
be so readily noticed. If the man has something so simple and so widely applicable that we
just paid $300 for a suit, an addi- still refer to it as Weber’s law. This law states that for
tional $75 for a sweater will not seem an average person to perceive a difference, two stimuli
excessive. The same applies to other must differ by a constant minimum percentage (not a
accessories, such as a shirt or shoes.
As a rule, people will almost always tMhyeersmAP_SaEf_2tee_Mr,odr1a6_tB.hinded r15t8han before, a more expen- ENGAGE 1/21/14 9:32 AM MyersAP_SE_2e
pay more for accessories if they buy sive purchase. Use Student Activity: Under-
standing Weber’s law from the TRM to further Active Learning
demonstrate this concept.
To apply Weber’s law, students need 3 quarters,
Cialdini, R. B. (1993). Influence: Science and practice 2 envelopes, and a pair of shoes. Have them
(3rd ed.). New York: HarperCollins. place one quarter in one envelope and the
remaining 2 quarters in the other. Lifting each
envelope, they can easily determine which is
heavier. Now have them put each envelope in
a shoe. When they lift the shoes, one at a time,
the weight difference will be imperceptible.

Coren, S., Ward, L. M., & Enns, J. T. (2003). Sensation
and perception (6th ed.). New York: Wiley.

158 Unit IV Sensation and Perception

MyersPsyAP_TE_2e_U04.indd 158 2/26/14 9:34 AM

Basic Principles of Sensation and Perception Module 16 159

constant amount). The exact proportion varies, depending on the stimulus. Two lights, for difference threshold the ENGAGE
example, must differ in intensity by 8 percent. Two objects must differ in weight by 2 per- minimum difference between two
cent. And two tones must differ in frequency by only 0.3 percent (Teghtsoonian, 1971). For stimuli required for detection 50 Active Learning
example, to be perceptibly different, a 50-ounce weight must differ from another by about percent of the time. We experience
an ounce, a 100-ounce weight by about 2 ounces. the difference threshold as a just A fun way to demonstrate the impor-
noticeable difference (or jnd). tance of sensory adaptation is to ask
Sensory Adaptation students what a day would be like if
Weber’s law the principle that, they felt different items they wore on
16-5 What is the function of sensory adaptation? to be perceived as different, two a daily basis like a wristwatch, glasses,
stimuli must differ by a constant socks, etc. Be descriptive as you ask
Entering your neighbors’ living room, you smell a musty odor. You wonder how they can minimum percentage (rather than a students about these items they are
stand it, but within minutes you no longer notice it. Sensory adaptation has come to your constant amount). wearing: Do you feel your socks grip-
rescue. When we are constantly exposed to a stimulus that does not change, we become less ping your ankles? Your watch squeez-
aware of it because our nerve cells fire less frequently. (To experience sensory adaptation, sensory adaptation diminished ing your wrist? Students become
move your watch up your wrist an inch: You will feel it—but only for a few moments.) sensitivity as a consequence of squirmy as they “feel” these items
constant stimulation. rather intensely!
Why, then, if we stare at an object without flinching, does it not vanish from sight? Be-
cause, unnoticed by us, our eyes are always moving. This continual flitting from one spot to “We need above all to know ENGAGE
another ensures that stimulation on the eyes’receptors continually changes (FIGURE 16.7). about changes; no one wants or
needs to be reminded 16 hours Active Learning
What if we actually could stop our eyes from moving? Would sights seem to vanish, a day that his shoes are on.”
as odors do? To find out, psychologists have devised ingenious instruments that maintain -NEUROSCIENTIST DAVID HUBEL (1979) Divide students into small groups and
a constant image on the eye’s inner surface. Imagine that we have fitted a volunteer, Mary, have one person in the group com-
with one of these instruments—a miniature projector mounted on a contact lens (FIGURE plete a simple task, such as completing
16.8a on the next page). When Mary’s eye moves, the image from the projector moves as a crossword puzzle or word find. Have
well. So everywhere that Mary looks, the scene is sure to go. the other members of the group test
different types of noise interference
If we project images through this instrument, what will Mary see? At first, she will see on the person’s ability to complete the
the complete image. But within a few seconds, as her sensory system begins to fatigue, task. They should record their results.
things get weird. Bit by bit, the image vanishes, only to reappear and then disappear—often Have them consider the following
in fragments (Figure 16.8b). questions:

Although sensory adaptation reduces our sensitivity, it offers an important benefit: free- ᭹ Does noise with words (reading
dom to focus on informative changes in our environment without being distracted by back- a story) interfere more than
ground chatter. Stinky or heavily perfumed classmates don’t notice their odor because, like noise without words (static or
you and me, they adapt to what’s constant and detect only change. Our sensory receptors yelling “blah, blah”)?

Figure 16.7 ᭹ Does music with words interfere
more than music without words?
The jumpy eye Our gaze jumps
from one spot to another every ᭹ How loud does the noise have to be
third of a second or so, as eye- for it to become distracting?
tracking equipment illustrated in this
photograph of Edinburgh’s Princes
Street Gardens (Henderson, 2007).
The circles represent fixations, and the
numbers indicate the time of fixation
in milliseconds (300 milliseconds =
three-tenths of a second).

John M. Henderson

1/21/14 9:32 AM E N G AG EMyersAP_SE_2e_Mod16_B.indd 159 1/21/14 9:32 AM

Active Learning and water until it becomes less bitter. The glass
of fresh water will taste sweet. The variability
Adaptation to the taste of one substance can in the taste of ordinary tap water following
affect the taste of another, either decreasing or adaptation to various substances will surprise
increasing our sensitivity to it. Using 3 glasses many students.
of water (one mixed with salt, one mixed Fisher, J. (1979). Body magic. New York: Stein & Day.
with vinegar, and one fresh), have a student
volunteer come to the front of the classroom. Basic Principles of Sensation and Perception
Have the student taste the saltwater and hold
it in his or her mouth for a time; it will gradually
taste less salty. If the student then takes a glass
of fresh water, it will taste bitter or sour. Have
another student volunteer come to the front
of the room and hold a mouthful of vinegar

Module 16 159

MyersPsyAP_TE_2e_U04.indd 159 2/20/14 8:09 AM

160 U n i t I V Sensation and Perception

CLOSE & ASSESS Figure 16.8 (a) (b)

Exit Assessment Sensory adaptation: Now you
see it, now you don’t!
Several concepts in this module may (a) A projector mounted on a contact
be difficult to understand and are lens makes the projected image
often confused. To assess whether move with the eye. (b) Initially, the
students understand these concepts, person sees the stabilized image,
ask them to give examples and provide but soon she sees fragments
definitions or compare and contrast fading and reappearing. (From
the following: “Stabilized images on the retina,” by
R. M. Pritchard. Copyright © 1961
᭹ Top-down vs. bottom-up Scientific American, Inc. All rights
processing reserved.)

᭹ Absolute vs. difference thresholds are alert to novelty; bore them with repetition and they free our attention for more impor-
tant things. We will see this principle again and again: We perceive the world not exactly as it
is, but as it is useful for us to perceive it.

Our sensitivity to changing stimulation helps explain television’s attention-grabbing pow-
er. Cuts, edits, zooms, pans, sudden noises—all demand attention.The phenomenon is irresist-
ible even to TV researchers. One noted that even during interesting conversations, “I cannot for
the life of me stop from periodically glancing over to the screen” (Tannenbaum, 2002).

Sensory adaptation even influences our perceptions of emotions. By creating a 50-50
morphed blend of an angry and a scared face, researchers showed that our visual system
adapts to a static facial expression by becoming less responsive to it (Butler et al., 2008)
(FIGURE 16.9).

Sensory adaptation and sensory thresholds are important ingredients in our percep-
tions of the world around us. Much of what we perceive comes not just from what’s “out
there” but also from what’s behind our eyes and between our ears.

Figure 16.9 Reprinted from Brain Research, Vol 1191, Andrea Butler, Ipek Oruc,
Christopher J. Fox, Jason J. S. Barton. Factors contributing to the
Emotion adaptation Gaze
at the angry face on the left for adaptation after effects of facial expression, Pg 116–126, 2008, with
20 to 30 seconds, then look at permission from Elsevier.
the center face (looks scared,
yes?). Then gaze at the scared
face on the right for 20 to 30
seconds, before returning to
the center face (now looks
angry, yes?).

Before You Move On

᭤ ASK YOURSELF

Can you recall a recent time when, your attention focused on one thing, you were oblivious
to something else (perhaps to pain, to someone’s approach, or to background music)?

᭤ TEST YOURSELF

Explain how Heather Sellers’ experience of prosopagnosia illustrates the difference between
sensation and perception.
Answers to the Test Yourself questions can be found in Appendix E at the end of the book.

MyersAP_SE_2e_Mod16_B.indd 160 1/21/14 9:32 AM MyersAP_SE_2e

160 Unit IV Sensation and Perception 2/20/14 8:09 AM

MyersPsyAP_TE_2e_U04.indd 160

Basic Principles of Sensation and Perception Module 16 161

Module 16 Review

16-1 What are sensation and perception? What • Researchers in psychophysics study the relationships
do we mean by bottom-up processing and
between stimuli’s physical characteristics and our
top-down processing? psychological experience of them.

• Sensation is the process by which our sensory receptors 16-4 What are the absolute and difference
thresholds, and do stimuli below the absolute
and nervous system receive and represent stimulus threshold have any influence on us?
energies from our environment. Perception is the process
of organizing and interpreting this information, enabling • Our absolute threshold for any stimulus is the minimum
recognition of meaningful events. Sensation and
perception are actually parts of one continuous process. stimulation necessary for us to be consciously aware of
it 50 percent of the time. Signal detection theory predicts
• Bottom-up processing is sensory analysis that begins at the how and when we will detect a faint stimulus amid
background noise. Individual absolute thresholds vary,
entry level, with information flowing from the sensory depending on the strength of the signal and also on our
receptors to the brain. Top-down processing is information experience, expectations, motivation, and alertness.
processing guided by high-level mental processes, as
when we construct perceptions by filtering information • Our difference threshold (also called just noticeable difference,
through our experience and expectations.
or jnd) is the difference we can discern between two
16-2 How much information do we consciously stimuli 50 percent of the time. Weber’s law states that
attend to at once? two stimuli must differ by a constant percentage (not a
constant amount) to be perceived as different.
• We selectively attend to, and process, a very limited portion of
• Priming shows that we can process some information
incoming information, blocking out much and often shifting
the spotlight of our attention from one thing to another. from stimuli below our absolute threshold for conscious
awareness. But the effect is too fleeting to enable people
• Focused intently on one task, we often display inattentional to exploit us with subliminal messages.

blindness (including change blindness) to other events and 16-5 What is the function of sensory adaptation?
changes around us.
• Sensory adaptation (our diminished sensitivity to constant
16-3 What three steps are basic to all our
sensory systems? or routine odors, sights, sounds, and touches) focuses our
attention on informative changes in our environment.
• Our senses (1) receive sensory stimulation (often using

specialized receptor cells); (2) transform that stimulation
into neural impulses; and (3) deliver the neural
information to the brain. Transduction is the process of
converting one form of energy into another.

Multiple-Choice Questions 2. What principle states that to be perceived as different, Answers to Multiple-Choice
two stimuli must differ by a minimum percentage rather Questions
1. What occurs when experiences influence our than a constant amount?
interpretation of data? 1. d
a. Absolute threshold 2. e
a. Selective attention b. Different threshold
b. Transduction c. Signal detection theory
c. Bottom-up processing d. Priming
d. Top-down processing e. Weber’s law
e. Signal detection theory

1/21/14 9:32 AM MyersAP_SE_2e_Mod16_B.indd 161 1/21/14 9:32 AM

Basic Principles of Sensation and Perception Module 16 161

MyersPsyAP_TE_2e_U04.indd 161 2/20/14 8:09 AM

162 U n i t I V Sensation and Perception

3. a 5. e 3. What do we call the conversion of stimulus energies, like 5. Tyshane went swimming with friends who did not want
4. c sights and sounds, into neural impulses? to get into the pool because the water felt cold. Tyshane
jumped in and after a few minutes declared, “It was cold
Answer to Practice FRQ 2 a. Transduction when I first got in, but now my body is used to it. Come
b. Perception on in!” Tyshane’s body became accustomed to the water
1 point: Absolute threshold is the mini- c. Priming due to
mum stimulation that can be detected d. Signal detection theory
50% of the time. e. Threshold a. perceptual set.
1 point: Difference threshold is the b. absolute threshold.
minimum change in stimulation a per- 4. Natalia is washing her hands and adjusts the faucet c. difference threshold.
son can detect 50% of the time. handle until the water feels just slightly hotter than it did d. selective attention.
1 point: Absolute threshold real-world before. Natalia’s adjustment until she feels a difference is e. sensory adaptation.
examples can include, but are not an example of
limited to, the following: (1) the light-
est wind Marisol can feel, or (2) the first a. a subliminal stimulus.
realization that it is snowing. b. an absolute threshold.
1 point: Difference threshold real- c. a difference threshold.
world examples can include, but are d. signal detection.
not limited to, the following: (1) being e. Weber’s law.
aware of a slight change in tem-
perature, or (2) being aware of a slight Practice FRQs 2. Marisol is planning a ski trip for spring break. Define
change in atmospheric pressure as absolute threshold and difference threshold, and explain
Marisol skis down the mountain. 1. Explain how bottom-up and top-down processes work how each one might play a role in her perception of the
together to help us decipher the world around us.. winter weather she will experience.

Answer (4 points)

1 point: Bottom-up processing starts at the sensory
receptors and works up to higher levels of processing.

1 point: Top-down processing constructs perceptions
from the sensory input by drawing on our experience and
expectations.

MyersAP_SE_2e_Mod16_B.indd 162 1/21/14 9:32 AM MyersAP_SE_2e

162 Unit IV Sensation and Perception 2/20/14 8:09 AM

MyersPsyAP_TE_2e_U04.indd 162

Influences on Perception Module 17 163

Module 17 © Nick Dolding/cultura/Corbis TEACH

Influences on Perception TRM Discussion Starter

Module Learning Objectives Use the Module 17 Fact or Falsehood?
student activity from the TRM to intro-
17-1 Explain how our expectations, contexts, emotions, and duce the concepts from this module.
motivation influence our perceptions.
TEACH
17-2 List the claims of ESP, and discuss the conclusions of most
research psychologists after putting these claims to the test. Teaching Tip

Perceptual Set perceptual set a mental Ask your class to shout out the answers
predisposition to perceive one to the following questions. “What do
17-1 How do our expectations, contexts, emotions, and motivation thing and not another. these letters spell?” (Write folk on the
influence our perceptions? board.) “How about these?” (Write
croak.) “And what do these letters
As everyone knows, to see is to believe. As we less fully appreciate, to believe is to see. spell?” (Write soak.) “What do we
Through experience, we come to expect certain results. Those expectations may give us call the white of an egg?” Students
a perceptual set, a set of mental tendencies and assumptions that greatly affects (top- will respond “yolk” even though the
down) what we perceive. Perceptual set can influence what we hear, taste, feel, and see. answer is “egg white.”

Consider: Is the image in the center picture of FIGURE 17.1 a young woman’s profile This activity demonstrates the
or an old woman? What we see in such a drawing can be influenced by first looking at power of perceptual set. Students get
either of the two unambiguous versions (Boring, 1930). into a pattern of spelling the word in
a particular way, so when one homo-
Everyday examples of perceptual set abound. In 1972, a British newspaper published phone word is introduced, they will
unretouched photographs of a “monster” in Scotland’s Loch Ness—“the most amazing spell it consistently with the pattern.

Figure 17.1 TEACH

Perceptual set Show Concept Connections
a friend either the left or
right image. Then show Perceptual set is similar to priming.
the center image and What we expect to see is often influ-
ask, “What do you see?” enced by what is around us.
Whether your friend reports
seeing a young woman’s
profile or an old woman
may depend on which of
the other two drawings
was viewed first. In each of
those images, the meaning
is clear, and it will establish
perceptual expectations.

1/21/14 9:32 AM E N G AG EMyersAP_SE_2e_Mod17_B.indd 163 1/21/14 9:32 AM

Active Learning

Use figure–ground illusions like the one in
Figure 17.1 to demonstrate perceptual set. Tell
half the class to imagine a nursing home while
the other half imagines a high school. See how
many in each group see the old woman or the
young woman.

Influences on Perception Module 17 163

MyersPsyAP_TE_2e_U04.indd 163 2/20/14 8:10 AM

164 U n i t I V Sensation and Perception

pictures ever taken,” stated the paper. If this information creates in you the same ex-
pectations it did in most of the paper’s readers, you, too, will see the monster in a simi-

lar photo in FIGURE 17.2. But when a skeptical researcher approached the
photos with different expectations, he saw a curved tree limb—as had others
the day the photo was shot (Campbell, 1986). With this different perceptual
set, you may now notice that the object is floating motionless, with ripples
outward in all directions—hardly what we would expect of a lively monster.
Once we have formed a wrong idea about reality, we have more difficulty see-
ing the truth.

Perceptual set can also affect what we hear. Consider the kindly airline pilot
who, on a takeoff run, looked over at his depressed co-pilot and said, “Cheer
up.” Expecting to hear the usual “Gear up,” the co-pilot promptly raised the wheels—before
they left the ground (Reason & Mycielska, 1982).

Figure 17.2
Believing is seeing What do you
perceive? Is this Nessie, the Loch Ness
monster, or a log?
ENGAGE © The New Yorker Collection, 2002, Leo Cullum from cartoonbank.com.
All Rights Reserved.
Active Learning Hulton Archive/Getty Images

Have students create their own percep-
tual set studies by packaging generic
foods and drinks in name-brand
packaging. They can then do taste
tests with their friends or family to see
whether the packaging matters. How
do the people judge the products:
same, better, or worse? Have students
discuss how perceptual set influences
people’s perceptions of the products.

TEACH Try This Perceptual set similarly affects taste. One experiment invited some bar patrons to
sample free beer (Lee et al., 2006). When researchers added a few drops of vinegar to a
Concept Connections When shown the phrase brand-name beer, the tasters preferred it—unless they had been told they were drinking
Mary had a vinegar-laced beer. Then they expected, and usually experienced, a worse taste. In another
Schemas are an important concept in a little lamb experiment, preschool children, by a 6-to-1 margin, thought french fries tasted better when
psychology. Swiss psychologist Jean served in a McDonald’s bag rather than a plain white bag (Robinson et al., 2007).
Piaget developed the idea of schemas many people perceive what they
to describe the ways in which we con- expect, and miss the repeated What determines our perceptual set? As Module 47 will explain, through experience we
ceptualize the world. These schemas word. Did you? form concepts, or schemas, that organize and allow us to interpret unfamiliar information.
help explain why we are vulnerable Our pre-existing schemas for old women and young women, for monsters and tree limbs,
to our perceptual sets. Schemas are “We hear and apprehend only all influence how we interpret ambiguous sensations with top-down processing.
further discussed in Unit IX. what we already half know.”
-HENRY DAVID THOREAU, JOURNAL, In everyday life, stereotypes about gender (another instance of perceptual set) can color
1860 perception. Without the obvious cues of pink or blue, people will struggle over whether to
call the new baby “he” or “she.” But told an infant is “David,” people (especially children)
may perceive “him” as bigger and stronger than if the same infant is called “Diana” (Stern
& Karraker, 1989). Some differences, it seems, exist merely in the eyes of their beholders.

Context Effects

A given stimulus may trigger radically different perceptions, partly because of our differing
perceptual set, but also because of the immediate context. Some examples:

MyersAP_SE_2e_Mod17_B.indd 164 1/21/14 9:33 AM MyersAP_SE_2e

164 Unit IV Sensation and Perception 2/20/14 8:10 AM

MyersPsyAP_TE_2e_U04.indd 164

Influences on Perception Module 17 165

Culture and context effects TEACH
What is above the woman’s head?
In a classic study from nearly a Diversity Connections
half-century ago, most East Africans
perceived the woman as balancing The drawing at the top of p. 165 is an
a metal box or can on her head excellent example of how culture influ-
and the family as sitting under a ences perception. Most Westerners
tree. Westerners, for whom corners have no trouble interpreting the scene
and boxlike architecture were of people sitting inside a dwelling.
more common, were more likely to They do not confuse the window with
perceive the family as being indoors, a box on the woman’s head. However,
with the woman sitting under a those from other cultures who do
window. (Adapted from Gregory & not share the same perceptual sets
Gombrich, 1973.) perceive the scene differently. Help
students see the perspective of others
• Imagine hearing a noise interrupted by the words “eel is on the wagon.” Likely, you with this picture.
would actually perceive the first word as wheel. Given “eel is on the orange,” you
would hear peel. This curious phenomenon, discovered by Richard Warren, suggests TEACH
that the brain can work backward in time to allow a later stimulus to determine how
we perceive an earlier one. The context Teaching Tip
creates an expectation that, top-down,
influences our perception (Grossberg, Use the figures throughout the unit
1995). to demonstrate to students these per-
ceptual concepts. Have students find
• Does the pursuing dog in FIGURE 17.3 their own examples of these and create
look bigger than the one being pursued? If a library of visual illusions to use with
so, you are experiencing a context effect. students. You might direct them to the
website http://dragon.uml.edu/psych/.
• How tall is the shorter player in
FIGURE 17.4?

Dennis Geppert/Holland Sentinel ENGAGE

Figure 17.3 Figure 17.4 Enrichment

The interplay between context and Big and “little” The “little guy” Research on context shows that situ-
emotional perception The context shown here is actually a 6’9” former ations can have a powerful effect on
makes the pursuing dog look bigger than Hope College basketball center who behavior:
the pursued. It isn’t. would tower over most of us. But
he seemed like a short player when ᭹ Studying should not occur while
matched in a semi-pro game against the lying in bed. Students who do
world’s tallest basketball player at that this often associate studying with
time, 7'9'' Sun Ming Ming from China. sleeping because they study where
they sleep. For effective studying, a
1/21/14 9:33 AM E N G AG EMyersAP_SE_2e_Mod17_B.indd 165 1/21/14 9:33 AM designated place should be created
where all the necessary supplies are
Active Learning available.

Have your teaching colleagues provide baby ᭹ Sleep researchers assisting those
pictures of themselves or their children that suffering from insomnia suggest
do not give away the baby’s gender. Have designating the bed for sleeping
students guess what gender the baby is and only and not for watching TV or
identify which cues they are using to deter- reading. People may come to
mine the gender. You can discuss with students associate the bed with those other
how we use our schemas and perceptual sets activities rather than with sleeping,
to make sense of ambiguous stimuli. which can hinder their ability to fall
asleep easily.

Influences on Perception Module 17 165

MyersPsyAP_TE_2e_U04.indd 165 2/20/14 8:10 AM

166 U n i t I V Sensation and Perception

TEACH “When you’re hitting the ball, Emotion and Motivation
it comes at you looking like a
Concept Connections grapefruit. When you’re not, Perceptions are influenced, top-down, not only by our expectations and by the context, but
it looks like a blackeyed pea.” also by our emotions and motivation.
Link this discussion of emotion and -FORMER MAJOR LEAGUE BASEBALL
motivation to the discussion of the PLAYER GEORGE SCOTT Hearing sad rather than happy music can predispose people to perceive a sad mean-
same topics in Unit VIII. How we ing in spoken homophonic words—mourning rather than morning, die rather than dye, pain
perceive the world is influenced by our rather than pane (Halberstadt et al., 1995).
current emotional state and whether
we are motivated to notice details. Researchers (Proffitt, 2006a,b; Schnall et al., 2008) have demonstrated the power of
emotions with other clever experiments showing that
ENGAGE
• walking destinations look farther away to those who have been fatigued by prior
Active Learning exercise.

Have students pick an influence on • a hill looks steeper to those who are wearing a heavy backpack or have just been
perception mentioned in the text and exposed to sad, heavy classical music rather than light, bouncy music. As with so many
devise a test of that concept that they of life’s challenges, a hill also seems less steep to those with a friend beside them.
can conduct with their peers. You can
use these as classroom demonstra- • a target seems farther away to those throwing a heavy rather than a light object at it.
tions or as a project students conduct
with fellow students outside class with Even a softball appears bigger when you are hitting well, observed other researchers, after
permission from the administration. asking players to choose a circle the size of the ball they had just hit well or poorly (Witt &
Proffitt, 2005). When angry, people more often perceive neutral objects as guns (Bauman &
DeSteno, 2010).

Motives also matter. Desired objects, such as a water bottle when thirsty, seem closer
(Balcetis & Dunning, 2010). This perceptual bias energizes our going for it. Our motives also
direct our perception of ambiguous images.

Emotions color our social perceptions, too. Spouses who feel loved and appreciated
perceive less threat in stressful marital events—“He’s just having a bad day” (Murray et al.,
2003). Professional referees, if told a soccer team has a history of aggressive behavior, will
assign more penalty cards after watching videotaped fouls (Jones et al., 2002).

***
Emotion and motivation clearly influence how we perceive sensations. But what to make of
extrasensory perception, which claims that perception can occur apart from sensory input? For
more on that question, see Thinking Critically About: ESP—Perception Without Sensation?

Before You Move On

᭤ ASK YOURSELF

Can you recall a time when your expectations have predisposed how you perceived a
person (or group of people)?

᭤ TEST YOURSELF

What type of evidence shows that, indeed, “there is more to perception than meets the
senses”?

Answers to the Test Yourself questions can be found in Appendix E at the end of the book.

MyersAP_SE_2e_Mod17_B.indd 166 1/21/14 9:33 AM MyersAP_SE_2e

166 Unit IV Sensation and Perception 2/20/14 8:10 AM

MyersPsyAP_TE_2e_U04.indd 166

Influences on Perception Module 17 167

Thinking Critically About TEACH

ESP—Perception Without Sensation? TRM Diversity Connections

17-2 What are the claims of ESP, and what Most research psychologists and scientists—including Teaching skepticism for ESP should
have most research psychologists 96 percent of the scientists in the U.S. National Academy be tempered so as not to alienate stu-
concluded after putting these claims to of Sciences—are skeptical that paranormal phenomena ex- dents with various religious beliefs and
the test? ist (McConnell, 1991). But reputable universities in many lo- experiences, such as beliefs in angels,
cations, including Great Britain, the Netherlands, and Australia, dreams as visions, etc. The goal of this
Without sensory input, are we capable of extrasensory per- have added faculty chairs or research units in parapsychology skepticism should be to avoid scam
ception (ESP)? Are there indeed people—any people—who (Turpin, 2005). These researchers perform scientific experiments artists rather than to dispel particular
can read minds, see through walls, or foretell the future? Nearly searching for possible ESP and other paranormal phenomena. belief systems. Use Student Activity:
half of Americans believe there are (AP, 2007; Moore, 2005). Before seeing how parapsychologists do research on ESP, let’s Belief in ESP Scale from the TRM to
consider some popular beliefs. assess your students’ opinions of the
The most testable and, for this unit, most relevant parapsy- existence of psychic or ESP abilities.
chological concepts are PREMONITIONS OR PRETENSIONS?
ENGAGE
• telepathy: mind-to-mind communication. Can psychics see into the future? Although one might wish for a
psychic stock forecaster, the tallied forecasts of “leading psychics” TRM Active Learning
• clairvoyance: perceiving remote events, such as a house reveal meager accuracy. During the 1990s, the tabloid psychics
on fire in another state. were all wrong in predicting surprising events. (Madonna did not Have students collect horoscopes or
become a gospel singer, the Statue of Liberty did not lose both other precognitive predictions from
• precognition: perceiving future events, such as an its arms in a terrorist blast, Queen Elizabeth did not abdicate her publications found in supermarket
unexpected death in the next month. throne to enter a convent.) And the new-century psychics have checkout aisles over a period of
missed the big-news events. Where were the psychics on 9/10 time. Have them record the predic-
Closely linked is psychokinesis, or “mind over matter,” such when we needed them? Why, despite a $50 million reward offered, tions made about different events
as levitating a table or influencing the roll of a die. (The claim could none of them help locate terrorist Osama bin Laden after or different astrological signs and
is illustrated by the wry request, “Will all those who believe in the horror of 9/11, or step forward to predict the impending stock compare those predictions with what
psychokinesis please raise my hand?”) crashes in 2008? In 30 years, unusual predictions have almost actually occurred. They can do this by
never come true, and psychics have virtually never anticipated any checking the newspapers for reports
If ESP is real, we would need to overturn the scientific un- of the year’s headline events (Emory, 2004, 2006). In 2010, when related to the predictions or keep a
derstanding that we are creatures whose minds are tied to our a mine collapse trapped 33 miners, the Chilean government re- journal of what happens in their lives
physical brains and whose perceptual experiences of the world portedly consulted four psychics. Their verdict? “They’re all dead” to check if their daily horoscope is
are built of sensations. Sometimes new evidence does overturn (Kraul, 2010). But 69 days later, all 33 were rescued. correct. What they will likely find is that
our scientific preconceptions. Science, as we will see through- predictions made by astrologers are
out this book, offers us various surprises—about the extent of Moreover, the hundreds of psychic visions offered to police usually ambiguous enough to apply
the unconscious mind, about the effects of emotions on health, departments have been no more accurate than guesses made to multiple situations, which begs the
about what heals and what doesn’t, and much more. by others (Nickell, 1994, 2005; Radford, 2010; Reiser, 1982). question: Can a prediction that applies
But their sheer volume does increase the odds of an occasional to many outcomes really be considered
correct guess, which psychics can then report to the media. accurate if it came true? Use Teacher
Police departments are wise to all this. When researchers asked Demonstration: Testing for ESP from
the police departments of America’s 50 largest cities whether the TRM for a simple classroom test of
they ever had used psychics, 65 percent said No (Sweat & ESP involving flipping a coin, which
Durm, 1993). Of those that had, not one had found them help- also provides an important lesson in
ful. Vague predictions can also later be interpreted (“retrofitted”) probability.

Dan Piraro extrasensory perception (ESP) the controversial claim
that perception can occur apart from sensory input; includes
telepathy, clairvoyance, and precognition.
parapsychology the study of paranormal phenomena,
including ESP and psychokinesis.

(continued on next page)

1/21/14 9:33 AM MyersAP_SE_2e_Mod17_B.indd 167 1/21/14 9:33 AM

Influences on Perception Module 17 167

MyersPsyAP_TE_2e_U04.indd 167 2/20/14 8:10 AM

168 U n i t I V Sensation and Perception

ENGAGE Thinking Critically About (continued)

TRM Online Activities to match events that provide a perceptual set for “understand- This scientific attitude has led both believers and skep-
ing” them. Nostradamus, a sixteenth-century French psychic, tics to agree that what parapsychology needs is a reproduc-
The following websites offer informa- explained in an unguarded moment that his ambiguous prophe- ible phenomenon and a theory to explain it. Parapsychologist
tion about scientific testing of psychic cies “could not possibly be understood till they were interpreted Rhea White (1998) spoke for many in saying that “the image
phenomena: after the event and by it.” of parapsychology that comes to my mind, based on nearly
44 years in the field, is that of a small airplane [that] has been
᭹ The James Randi Educational Are the spontaneous “visions” of everyday people any more perpetually taxiing down the runway of the Empirical Science
Foundation homepage at accurate? Do dreams, for example, foretell the future, as people Airport since 1882 . . . its movement punctuated occasionally
www.randi.org. from both Eastern and Western cultures tend to believe—mak- by lifting a few feet off the ground only to bump back down
ing some people more reluctant to fly after dreaming of a plane on the tarmac once again. It has never taken off for any sus-
᭹ The Rhine Research Center Web site crash (Morewedge & Norton, 2009)? Or do they only seem to tained flight.”
at www.rhine.org. do so when we recall or reconstruct them in light of what has
already happened? Two Harvard psychologists tested the pro- How might we test ESP claims in a controlled, reproducible
After searching these sites, have stu- phetic power of dreams after superhero aviator Charles Lind- experiment? An experiment differs from a staged demonstra-
dents address the following questions: bergh’s baby son was kidnapped and murdered in 1932, but tion. In the laboratory, the experimenter controls what the “psy-
before the body was discovered (Murray & Wheeler, 1937). chic” sees and hears. On stage, the psychic controls what the
᭹ Why are psychics generally When invited to report their dreams about the child, 1300 vi- audience sees and hears.
unwilling to be scientifically tested? sionaries submitted dream reports. How many accurately en-
visioned the child dead? Five percent. And how many also The search for a valid and reliable test of ESP has resulted
᭹ Do you think paranormal correctly anticipated the body’s location—buried among trees? in thousands of experiments. After digesting data from 30 such
phenomena is a worthy scientific Only 4 of the 1300. Although this number was surely no better studies, parapsychologist Lance Storm and his colleagues
subject to study? Why or why not? than chance, to those 4 dreamers the accuracy of their appar- (2010a,b) concluded that, given participants with experience or
ent precognitions must have seemed uncanny. belief in ESP, there is “consistent and reliable” parapsychological
Use Teacher Demonstration: ESP evidence. Psychologist Ray Hyman (2010), who has been
Trick—Precognition (Playing Card Trick) Given the billions of events in the world each day, and given scrutinizing parapsychological research since 1957, replies that if
from the TRM to help underline the enough days, some stunning coincidences are sure to occur. this is the best evidence, it fails to impress: “Parapsychology will
necessity for rigid experimental control By one careful estimate, chance alone would predict that more achieve scientific acceptability only when it provides a positive
in evaluating ESP claims. than a thousand times a day someone on Earth will think of theory with . . . independently replicable evidence. This is
another person and then within the next five minutes will learn something it has yet to achieve after more than a century.”
TEACH of that person’s death (Charpak & Broch, 2004). Thus, when
explaining an astonishing event, we should “give chance a Daryl Bem (2011), a respected social psychologist, has
TRM Concept Connections chance” (Lilienfeld, 2009). With enough time and people, the been a skeptic of stage psychics; he once quipped that “a psy-
improbable becomes inevitable. chic is an actor playing the role of a psychic” (1984). Yet he has
Remind students of the following con- reignited hopes for replicable evidence with nine experiments
cepts from scientific thinking in Unit II, “To be sure of hitting the target, shoot first and call whatever you that seemed to show people anticipating future events. In one,
especially when considering ESP and hit the target.” -WRITER-ARTIST ASHLEIGH BRILLIANT, 1933
other paranormal phenomena: “At the heart of science is an essential tension between two
“A person who talks a lot is sometimes right.” -SPANISH PROVERB seemingly contradictory attitudes—an openness to new ideas,
᭹ Correlation does not mean no matter how bizarre or counterintuitive they may be, and the
causation. Just because events most ruthless skeptical scrutiny of all ideas, old and new.”
occur together does not mean that -CARL SAGAN (1987)
they cause each other.
PUTTING ESP TO EXPERIMENTAL TEST Magician Harry Houdini after fooling Sir Arthur Conan Doyle
᭹ Confirmation bias occurs when we with a pseudo-psychic trick: “Now I beg of you, Sir Arthur,
only look for evidence that supports When faced with claims of mind reading or out-of-body travel do not jump to the conclusion that certain things you see are
our beliefs and ignore evidence or communication with the dead, how can we separate bizarre necessarily ‘supernatural,’ or with the work of ‘spirits,’ just
that refutes them. Many people ideas from those that sound strange but are true? At the heart because you cannot explain them.” -QUOTED BY WILLIAM KALUSH AND
believe in parapsychology because of science is a simple answer: Test them to see if they work. If LARRY SLOMAN, THE SECRET LIFE OF HOUDINI, 2007
they rely only on the evidence that they do, so much the better for the ideas. If they don’t, so much
supports their beliefs. the better for our skepticism.

Use Teacher Demonstration: ESP MyersAP_SE_2e_Mod17_B.indd 168 1/21/14 9:33 AM MyersAP_SE_2e
Trick—Precognition (Newspaper Arti-
cle Trick) from the TRM to demonstrate
a simple—yet doctored—newspaper
article to demonstrate precognitive
abilities.

168 Unit IV Sensation and Perception 2/20/14 8:10 AM

MyersPsyAP_TE_2e_U04.indd 168

Influences on Perception Module 17 169

Thinking Critically About (continued) ENGAGE

when an erotic scene was about to appear on a screen in one of Courtesy of Claire Cole TRM Active Learning
two randomly selected positions, Cornell University participants
guessed right 53.1 percent of the time (beating 50 percent by Testing psychic powers in the British population Have students create their own
a small but statistically significant margin). In another, people University of Hertfordshire psychologists created a “mind machine” experimental conditions under which
viewed a set of words, took a recall test of those words, and to see if people can influence or predict a coin toss (Wiseman & they would like to test ESP. Use this
then rehearsed a randomly selected subset of those words. Greening, 2002). Using a touch-sensitive screen, visitors to festivals activity as a check of their knowledge
People better remembered the rehearsed words—even when around the country were given four attempts to call heads or tails. of research methodology learned from
the rehearsal took place after the recall test. The upcoming Using a random-number generator, a computer then decided the Unit II. Use any of the following simple
rehearsal—a future event—apparently affected their ability to outcome. When the experiment concluded in January 2000, nearly ESP tests from the TRM:
recall words. 28,000 people had predicted 110,959 tosses—with 49.8 percent
correct. Teacher Demonstration: ESP
Bem wonders if his “anomalous” findings reflect an evolu- Trick—Clairvoyance
tionary advantage to those who can precognitively anticipate one need only produce a single person who can demonstrate Teacher Demonstration: ESP Trick—
future dangers. Critics scoff. “If any of his claims were true,” a single, reproducible ESP event. (To refute those who say pigs Mental Telepathy (Gray Elephant in
wrote cognitive scientist Douglas Hofstadter (2011), “then all of can’t talk would take but one talking pig.) So far, no such person Denmark Trick)
the bases underlying contemporary science would be toppled, has emerged. Teacher Demonstration: ESP
and we would have to rethink everything about the nature of the Trick—Mental Telepathy (Telephone
universe.” Moreover, if future events retroactively affect present Before You Move On Book Trick)
feelings, then why can’t people intuitively predict casino out-
comes or stock market futures? ᭤ ASK YOURSELF CLOSE & ASSESS

Despite Bem’s research having survived critical reviews by a Have you ever had what felt like an ESP experience? Exit Assessment
top-tier journal, other critics found the methods “badly flawed” Can you think of an explanation other than ESP for that
(Alcock, 2011) or the statistical analyses “biased” (Wagenmak- experience? Provide students with the following
ers et al., 2011). “A result—especially one of this importance— scenario (or a similar one of your own
must recur several times in tests by independent and skeptical ᭤ TEST YOURSELF choosing):
researchers to gain scientific credibility,” observed astronomer
David Helfand (2011). “I have little doubt that Professor Bem’s What is the field of study that researches claims of You are enjoying dinner with your
experiments will fail this test.” extrasensory perception (ESP)? family at a local restaurant. A large
group of people, both male and
Anticipating such skepticism, Bem has made his computer Answers to the Test Yourself questions can be found in Ap- female, enters the restaurant sing-
materials available to anyone who wishes to replicate his stud- pendix E at the end of the book. ing and talking loudly. The people
ies, and replications are now under way. One research team has continue to speak and sing loudly
already conducted five replications of Bem’s recall experiments throughout their time in the res-
at various universities and found no precognition (Galak et al., taurant. How do you perceive this
2011). Regardless of the outcomes, science will have done its situation and explain this group’s
work. It will have been open to a finding that challenges its own behavior? Use your knowledge of
worldview, and then, through follow-up research, it will have as- expectations/set, context, emotions,
sessed its validity. And that is how science sifts crazy-sounding and motivations to craft your answer.
ideas, leaving most on the historical waste heap while occa-
sionally surprising us. Use students’ explanations to deter-
mine how well they understand the
One skeptic, magician James Randi, has had a longstand- concepts in this module.
ing offer of $1 million to be given “to anyone who proves a genu-
ine psychic power under proper observing conditions” (Randi,
1999; Thompson, 2010). French, Australian, and Indian groups
have made similar offers of up to 200,000 euros (CFI, 2003).
Large as these sums are, the scientific seal of approval would
be worth far more. To refute those who say there is no ESP,

1/21/14 9:33 AM MyersAP_SE_2e_Mod17_B.indd 169 1/21/14 9:33 AM

Influences on Perception Module 17 169

MyersPsyAP_TE_2e_U04.indd 169 2/20/14 8:10 AM

170 U n i t I V Sensation and Perception

Module 17 Review

17-1 How do our expectations, contexts, 17-2 What are the claims of ESP, and what have
emotions, and motivation influence our most research psychologists concluded
after putting these claims to the test?
perceptions?
• Parapsychology is the study of paranormal phenomena,
• Perceptual set is a mental predisposition that functions as a
including extrasensory perception (ESP) and psychokinesis.
lens through which we perceive the world.
• The three most testable forms of ESP are telepathy (mind-
• Our learned concepts (schemas) prime us to organize and
to-mind communication), clairvoyance (perceiving remote
interpret ambiguous stimuli in certain ways. events), and precognition (perceiving future events).

• Our physical and emotional context, as well as our • Skeptics argue that (1) to believe in ESP, you must believe

motivation, can create expectations and color our the brain is capable of perceiving without sensory input,
interpretation of events and behaviors. and (2) researchers have been unable to replicate ESP
phenomena under controlled conditions.
Answers to Multiple-Choice Multiple-Choice Questions
Questions 3. Which of the following is produced by perceptual set?
1. What do we call a mental predisposition that influences a. Not noticing that the songs change in a restaurant
1. b 3. d our interpretation of a stimulus? b. Noticing a difference in the weight of a friend from
2. a one week to the next
a. A context effect c. Moving an arm quickly so that a mosquito flies away
b. Perceptual set d. Surprise at hearing an Oklahoma cowboy speak with
c. Extrasensory perception a British accent
d. Emotion e. Not noticing a watch on your wrist as the day
e. Motivation goes on

2. Kimberly tells her brother to put on a suit on a warm
summer day. Kimberly’s brother knows to put on a
swimsuit instead of a business suit because of

a. context.
b. ESP.
c. precognition.
d. bottom-up processing.
e. clairvoyance.

Answer to Practice FRQ 2 Practice FRQs 1 point: Clairvoyance: Martha would be able to perceive things
happening at a distance; that is, a cousin who lives in another
1 point: Context effects: Environmen- 1. Martha is convinced she has extrasensory perception. state just burnt her hand on the oven, and Martha feels it.
tal factors can influence perception. Explain what Martha’s specific abilities would be if she
For example, a tall basketball player had each of the following forms of ESP: 1 point: Precognition: Martha would be able to see future
might look short when standing next • Telepathy events happen; that is, she knows a pop quiz will take place
to a much taller player. • Clairvoyance next week.
• Precognition
1 point: Emotion: Mood can influence Then, briefly explain why you should doubt her claims. 1 point: There has never been a conclusive scientific
perception. For example, happy or sad demonstration of extrasensory ability.
music can alter one’s perception of Answer
ambiguous words and scenes. 2. How can context effects, emotions, and motivation
1 point: Telepathy: Martha would be able to use mind-to- trigger different perceptions of a single stimulus?
1 point: Motivation: Motivation can mind communication; that is, she is able to read someone’s
influence perception. For example, a mind. (3 points)
water bottle can seem closer when one
is thirsty. MyersAP_SE_2e_Mod17_B.indd 170 1/21/14 9:33 AM MyersAP_SE_2e

170 Unit IV Sensation and Perception 2/20/14 8:10 AM

MyersPsyAP_TE_2e_U04.indd 170

Vision Module 18 171

Module 18 TEACH

Vision © Randy Lincks/Corbis TRM Discussion Starter

Module Learning Objectives Use the Module 18 Fact or Falsehood?
student activity from the TRM to intro-
18-1 Describe the characteristics of visible light, and explain the duce the concepts from this module.
process by which the eye transforms light energy into neural
messages. ENGAGE

18-2 Describe how the eye and brain process visual information. Online Activities

18-3 Discuss the theories that help us understand color vision. Vision Science is a site that provides
recent research and activities related
18-1 What is the energy that we see as wavelength the distance from the peak of one light to human and animal visual sys-
visible light, and how does the eye or sound wave to the peak of the next. Electromagnetic tems. Use the following website to
transform light energy into neural wavelengths vary from the short blips of cosmic rays to enhance students’ understanding of
messages? the long pulses of radio transmission. our visual system: Vision Science at
http://visionscience.com.
Our eyes receive light energy and transduce (trans- White Prism Figure 18.1
form) it into neural messages that our brain then light TEACH
processes into what we consciously see. How does The wavelengths we
such a taken-for-granted yet remarkable thing see What we see as Interdisciplinary
happen? light is only a tiny slice Connections
of a wide spectrum of
The Stimulus Input: electromagnetic energy, Team with your school’s physics
Light Energy which ranges from instructor to give a lesson on the
gamma rays as short as physics of light. Light is an interesting
When you look at a bright red tulip, what strikes the diameter of an atom phenomenon that behaves both like
your eyes is not particles of the color red but pulses to radio waves over a mile waves and like particles. Our ability
of electromagnetic energy that your visual system long. The wavelengths to see color depends on the wave
perceives as red. What we see as visible light is visible to the human eye properties of light. Objects reflect the
but a thin slice of the whole spectrum of electro- (shown enlarged) extend wavelength of their colors back to the
magnetic energy, ranging from imperceptibly short from the shorter waves eye and absorb all other wavelengths
gamma waves to the long waves of radio transmis- of blue-violet light to the of light. A possible guest speaker for
sion (FIGURE 18.1). Other organisms are sensitive longer waves of red light. this lesson could be an astrophysicist,
to differing portions of the spectrum. Bees, for in- who might address such issues as
stance, cannot see what we perceive as red but can 400 500 600 700 how astrophysicists use the properties
see ultraviolet light. of light to determine the age of the
Part of spectrum visible universe.
Two physical characteristics of light help deter- to humans
mine our sensory experience of them. Light’s wave-
length—the distance from one wave peak to the next Gamma X-rays Ultra- Infrared Radar Broadcast
rays violet rays bands
rays

10–5 10–3 10–1 101 103 105 107 109 1011 1013
Wavelength in nanometers (billionths of a meter)

1/21/14 9:33 AM T E AC HMyersAP_SE_2e_Mod18_B.indd 171 1/21/14 9:33 AM

Teaching Tip

Have students draw, with the appropriate
colored crayon, what the different wavelengths
of light would look like. For instance, a bright
red color would have a long wavelength, one
with a great (tall) amplitude, whereas a dull
blue color would have a short wavelength with
a small (short) amplitude. Have them consult a
physics textbook or search online for help with
the colors between red and blue. Students with
learning difficulties might appreciate this more
tactile approach to understanding the relation-
ship between colors and wavelength.

Vision Module 18 171

MyersPsyAP_TE_2e_U04.indd 171 2/20/14 10:42 AM

172 U n i t I V Sensation and Perception

TEACH Figure 18.2 Short wavelength = high frequency Great amplitude
(bluish colors; high-pitched sounds) (bright colors; loud sounds)
Common Pitfalls The physical properties of
waves (a) Waves vary in wavelength Long wavelength = low frequency Small amplitude
Vision and audition use similar terms (the distance between successive (reddish colors; low-pitched sounds) (dull colors; quiet sounds)
to discuss the different stimuli that are peaks). Frequency, the number of
processed by our visual and auditory complete wavelengths that can pass (a) (b)
systems. This is because both visual a point in a given time, depends
and auditory stimuli work in waves, so on the wavelength. The shorter the
the characteristics of waves are similar wavelength, the higher the frequency.
for both light and sound. (For more on Wavelength determines the perceived
sound waves, see Module 20. ) color of light (and also the pitch
of sound). (b) Waves also vary in
᭹ Wavelength determines the quality amplitude (the height from peak to
of the waves (for vision, color; for trough). Wave amplitude determines
sound, pitch) the brightness of colors (and also the
loudness of sounds).
᭹ Amplitude determines the intensity
of the waves (for vision, brightness; hue the dimension of color that (FIGURE 18.2a)—determines its hue (the color we experience, such as the tulip’s red petals
for sound, loudness) is determined by the wavelength or green leaves). Intensity, the amount of energy in light waves (determined by a wave’s
of light; what we know as the color amplitude, or height), influences brightness (Figure 18.2b). To understand how we transform
TEACH names blue, green, and so forth. physical energy into color and meaning, we first need to understand vision’s window, the eye.

Interdisciplinary intensity the amount of energy The Eye
Connections in a light or sound wave, which we
perceive as brightness or loudness, Light enters the eye through the cornea, which protects the eye and bends light to provide
Invite your school’s art or photography as determined by the wave’s focus (FIGURE 18.3). The light then passes through the pupil, a small adjustable opening.
teacher to explain how a camera is sim- amplitude. Surrounding the pupil and controlling its size is the iris, a colored muscle that dilates or
ilar to the eye. Cameras use the eye as constricts in response to light intensity and even to inner emotions. (When we’re feeling
a model for how much light to let in to pupil the adjustable opening in amorous, our telltale dilated pupils and dark eyes subtly signal our interest.) Each iris is so
create a correct photograph of a given the center of the eye through which distinctive that an iris-scanning machine can confirm your identity.
image or situation. Have the teacher light enters.
cover any of the following topics: Behind the pupil is a lens that focuses incoming light rays into an image on the retina,
iris a ring of muscle tissue that a multilayered tissue on the eyeball’s sensitive inner surface. The lens focuses the rays by
᭹ Why certain film is important to use forms the colored portion of the eye changing its curvature in a process called accommodation.
for different situations and images around the pupil and controls the
size of the pupil opening. For centuries, scientists knew that when an image of a candle passes through a small
᭹ Why a flash is important and when opening, it casts an inverted mirror image on a dark wall behind. If the retina receives this
it should be used lens the transparent structure sort of upside-down image, as in Figure 18.3, how can we see the world right side up?
behind the pupil that changes shape The ever-curious Leonardo da Vinci had an idea: Perhaps the eye’s watery fluids bend the
᭹ Creative ways photographers to help focus images on the retina. light rays, reinverting the image to the upright position as it reaches the retina. But then in
use the camera’s features to take 1604, the astronomer and optics expert Johannes Kepler showed that the retina does receive
interesting pictures retina the light-sensitive inner upside-down images of the world (Crombie, 1964). And how could we understand such a
surface of the eye, containing world? “I leave it,” said the befuddled Kepler, “to natural philosophers.”
the receptor rods and cones plus
layers of neurons that begin the
processing of visual information.

accommodation the process by
which the eye’s lens changes shape to
focus near or far objects on the retina.

Figure 18.3 Lens Retina
Pupil
The eye Light rays reflected from a Fovea
candle pass through the cornea, pupil, Iris (point of
and lens. The curvature and thickness Cornea central focus)
of the lens change to bring nearby
or distant objects into focus on the © Pascal Goetgheluck/ Optic nerve
retina. Rays from the top of the candle Science Source to brain’s
strike the bottom of the retina, and visual cortex
those from the left side of the candle
strike the right side of the retina. The
candle’s image on the retina thus
appears upside down and reversed.

Blind spot

T E AC HMyersAP_SE_2e_Mod18_B.indd 172 1/21/14 9:33 AM MyersAP_SE_2e

Common Pitfalls

The word accommodation means different
things in different contexts. For this unit,
accommodation means the ways in which the
muscles of the eye change the shape of the
lens to focus light onto the retina. In
Unit IX, accommodation means the ways in
which we change our schemas to incorporate
new information we learn.

172 Unit IV Sensation and Perception 2/20/14 8:10 AM

MyersPsyAP_TE_2e_U04.indd 172

Vision Module 18 173

Eventually, the answer became clear: The retina doesn’t “see” a whole image. Rather, AP® Exam Tip ENGAGE
its millions of receptor cells convert particles of light energy into neural impulses and
forward those to the brain. There, the impulses are reassembled into a perceived, upright- There’s a lot of vocabulary here. Active Learning
seeming image. Make sure you understand the
name and the function of each of Nearsightedness occurs when the lens
The Retina the parts of the eye. To learn how focuses objects in front of the retina.
all the parts fit together, it may help Farsightedness occurs when the lens
If you could follow a single light-energy particle into your eye, you would first make your to make rough sketches (you don’t focuses objects behind the retina.
way through the retina’s outer layer of cells to its buried receptor cells, the rods and need to be an artist to try this!) Using an overhead projector, have stu-
cones (FIGURE 18.4). There, you would see the light energy trigger chemical changes and then compare your sketches dents imagine the screen is the retina.
that would spark neural signals, activating nearby bipolar cells. The bipolar cells in turn with Figures 18.3 and 18.4. You’ll When the projector is blurred in either
would activate the neighboring ganglion cells, whose axons twine together like the strands be better off making several quick, direction, you have to move the projec-
of a rope to form the optic nerve. That nerve will carry the information to your brain, rough sketches than one time- tor or the screen in order to focus it.
where your thalamus stands ready to distribute the information. The optic nerve can send consuming, nicely drawn one.
nearly 1 million messages at once through its nearly 1 million ganglion fibers. (The audi- ENGAGE
tory nerve, which enables hearing, carries much less information through its mere 30,000 rods retinal receptors that detect
fibers.) We pay a small price for this eye-to-brain highway. Where the optic nerve leaves black, white, and gray; necessary TRM Enrichment
the eye, there are no receptor cells—creating a blind spot (FIGURE 18.5 on the next for peripheral and twilight vision,
page). Close one eye and you won’t see a black hole, however. Without seeking your ap- when cones don’t respond. What is red eye, that annoying red
proval, your brain fills in the hole. dot that appears in people’s eyes in
cones retinal receptor cells that pictures, and why does it occur? Usu-
Rods and cones differ in where they’re found and in what they do (TABLE 18.1 on the are concentrated near the center ally, red eye occurs in pictures where
next page). Cones cluster in and around the fovea, the retina’s area of central focus (see Fig- of the retina and that function in the surrounding illumination is dim,
ure 18.3). Many have their own hotline to the brain: Each one transmits to a single bipolar daylight or in well-lit conditions. so the camera’s flash must be used to
cell that helps relay the cone’s individual message to the visual cortex, which devotes a large The cones detect fine detail and take an accurate picture. The flash is so
area to input from the fovea. These direct connections preserve the cones’ precise informa- give rise to color sensations. quick that the iris doesn’t have time to
tion, making them better able to detect fine detail. contract, making the pupil big enough
optic nerve the nerve that carries to see right through to the red retina!
Rods have no such hotline; they share bipolar cells with other rods, sending combined neural impulses from the eye to the Cameras with so-called “red-eye reduc-
messages. To experience this rod-cone difference in sensitivity to details, pick a word in this brain. tion” features provide a series of quick
sentence and stare directly at it, focusing its image on the cones in your fovea. Notice that flashes that warn the eye that a picture
blind spot the point at which the is about to be taken. The iris reacts to
optic nerve leaves the eye, creating the light pulses and shrinks the pupil
a “blind” spot because no receptor so that the retina is protected from the
cells are located there. bright flash.

fovea the central focal point in Use Student Activity: Locating the
the retina, around which the eye’s Retinal Blood Vessels from the TRM to
cones cluster. demonstrate properties of the retina.

1. Light entering eye triggers 2. Chemical reaction in turn Figure 18.4 ENGAGE
photochemical reaction in rods activates bipolar cells.
and cones at back of retina. The retina’s Applying Science
Light 3 reaction to light
2 Have students conduct an experiment
Light 1 to see which type of red-eye reduction
flash leads to the lowest amount of red
Ganglion Cone eye in a picture. Be sure they include
cell Rod students who have both light colored
eyes and darker colored eyes to control
Bipolar Neural for eye color. See Module 2 for a discus-
cell impulse sion of different research methods to
use for this type of study.
3

2

1

Cross section of retina Optic nerve To the brain’s visual
cortex via the thalamus

3. Bipolar cells then activate the ganglion cells, the axons of which
converge to form the optic nerve. This nerve transmits information
to the visual cortex (via the thalamus) in the brain.

1/21/14 9:33 AM E N G AG EMyersAP_SE_2e_Mod18_B.indd 173 1/21/14 9:33 AM

Active Learning look at the image in their peripheral vision,
focusing their foveal vision just to the side of
Have students test their foveal vision in the the object they want to see. They should note
dark as a homework project. Have them go in that the object becomes clearer and more
their backyards or in a darkened room (with detailed when they don’t look at it directly,
light only from ambient sources) and try to because in dim light the cones in the fovea are
focus their central vision on an object in the not activated but the rods in the periphery are.
environment. They should reflect on how
detailed the object appears. Then, have them

Vision Module 18 173

MyersPsyAP_TE_2e_U04.indd 173 2/20/14 10:42 AM

174 U n i t I V Sensation and Perception

ENGAGE Figure 18.5

Active Learning The blind spot There are no receptor cells where
the optic nerve leaves the eye. This creates a blind
Extend the text’s blind-spot activity by spot in your vision. To demonstrate, first close your
having students notice what exactly left eye, look at the spot, and move the page to a
fills the space where the blind spot is. distance from your face at which one of the cars
The space is actually white, not gray or disappears (which one do you predict it will be?).
black as one would expect. Students Repeat with the other eye closed—and note that
can even draw a line around the car. now the other car disappears. Can you explain why?
This time they will notice the line
continues as the brain creates what fills words a few inches off to the side appear blurred? Their image strikes the outer regions of
the blind spot based on the surround- your retina, where rods predominate. Thus, when driving or biking, you can detect a car in
ing stimuli. your peripheral vision well before perceiving its details.

ENGAGE Cones also enable you to perceive color. In dim light they become ineffectual, so you see
no colors. Rods, which enable black-and-white vision, remain sensitive in dim light. Several
Enrichment rods will funnel their faint energy output onto a single bipolar cell. Thus, cones and rods
each provide a special sensitivity—cones to detail and color, and rods to faint light.
By deliberately aiming the blind spot,
one can block out any appropriately Table 18.1 Receptors in the Human Omikron/Science Source
sized object. Legend has it that King Eye: Rod-Shaped Rods and Cone-
Charles II of England did this with Shaped Cones
his courtiers. V. S. Ramachandran
reported, “He used to make their heads Cones Rods
disappear. One story is that he used to
do it to people he had sentenced to Number 6 million 120 million
die, to see what they would look like
without their heads.” Location in retina Center Periphery

TEACH Sensitivity in dim light Low High

Flip It Color sensitivity High Low

Students can get some additional help Detail sensitivity High Low
understanding the role of rods and
cones by watching the Flip It Video: When you enter a darkened theater or turn off the light at night, your eyes adapt.Your
Rods and Cones in the Retina. pupils dilate to allow more light to reach your retina, but it typically takes 20 minutes or
more before your eyes fully adapt.You can demonstrate dark adaptation by closing or cover-

ing one eye for up to 20 minutes. Then make the light in the room not quite bright
enough to read this book with your open eye. Now open the dark-adapted eye
and read (easily). This period of dark adaptation matches the average natural
twilight transition between the Sun’s setting and darkness. How wonderfully

Andrey Armyagov /Shutterstock made we are.

Visual Information Processing

18-2 How do the eye and the brain process visual information?

Visual information percolates through progressively more abstract levels on its path
through the thalamus and on to the visual cortex. At the entry level, information process-
ing begins in the retina’s neural layers, which are actually brain tissue that has migrated
to the eye during early fetal development. These layers don’t just pass along electrical im-
pulses; they also help to encode and analyze sensory information. The third neural layer
in a frog’s eye, for example, contains the “bug detector” cells that fire only in response to
moving fly-like stimuli.

E N G AG EMyersAP_SE_2e_Mod18_B.indd 174 1/21/14 9:33 AM MyersAP_SE_2e

Active Learning Move in a semicircle toward the student’s cen-
ter of vision, asking periodically if the student
Because cones detect color and rods do not, can tell what color the marker is. Repeated
students might not realize that their peripheral guessing will prove incorrect until the marker is
vision is very poor at judging color. Have a stu- close to the center of the field of vision where
dent sit in a chair and fixate on a point straight the cones reside.
ahead. Stand to the side of the student, at a
180° angle, with a colored marker or piece of
colored paper against a neutral background.

174 Unit IV Sensation and Perception 2/20/14 8:10 AM

MyersPsyAP_TE_2e_U04.indd 174

Vision Module 18 175

After processing by your retina’s nearly 130 million receptor rods and cones, informa- TEACH
tion travels to your bipolar cells, then to your million or so ganglion cells, and through their
axons making up the optic nerve to your brain. Any given retinal area relays its information Common Pitfalls
to a corresponding location in the visual cortex, in the occipital lobe at the back of your brain
(FIGURE 18.6). The cells that make up the retina seem
backward. The rods and cones are
The same sensitivity that enables retinal cells to fire messages can lead them to misfire, located at the very back of the retina.
as you can demonstrate for yourself. Turn your eyes to the left, close them, and then gently The bipolar and ganglion cells are
rub the right side of your right eyelid with your fingertip. Note the patch of light to the left, stacked on top of the rods and cones in
moving as your finger moves. Why do you see light? Why at the left? layers. The rods and cones interpret the
light first, even though the light passes
Your retinal cells are so responsive that even pressure triggers them. But your brain through the bipolar and ganglion cells
interprets their firing as light. Moreover, it interprets the light as coming from the left—the before it hits those light-sensitive cells.
normal direction of light that activates the right side of the retina.
TEACH
Visual area Figure 18.6
of the thalamus Concept Connections
Pathway from the eyes to the
Optic visual cortex Ganglion axons Connect this topic to neuroscience
nerve forming the optic nerve run to the in Unit III by reminding students that
thalamus, where they synapse with visual processing occurs in the occipital
neurons that run to the visual cortex. lobe of the brain rather than in the eye.
The occipital lobe is located in the back
Retina of the brain, just above the cerebellum.
Students can look back at Figures 12.1,
Visual 12.5, and 12.6 as a refresher.
cortex
TEACH
Feature Detection feature detectors nerve cells in
the brain that respond to specific Flip It
David Hubel and Torsten Wiesel (1979) received a Nobel Prize for their work on feature features of the stimulus, such as
detectors. These specialized neurons in the occipital lobe’s visual cortex receive infor- shape, angle, or movement. Students can get some additional help
mation from individual ganglion cells in the retina. Feature detector cells derive their understanding how feature detectors
name from their ability to respond to a scene’s specific features—to particular edges, lines, AP® Exam Tip work by watching the Flip It Video:
angles, and movements. These cells pass this information to other cortical areas, where Feature Detectors.
teams of cells (supercell clusters) respond to more complex patterns. As we noted in Mod- Warning! Sometimes students
ule 12, one temporal lobe area by your right ear (FIGURE 18.7 on the next page) enables spend so much time mastering
you to perceive faces and, thanks to a specialized neural network, to recognize them from the parts of the eye that they
varied viewpoints (Connor, 2010). If this region were damaged, you might recognize other skim over the part you’re about to
forms and objects, but, like Heather Sellers, not familiar faces. When researchers tempo- read. Do not forget that you see
rarily disrupt the brain’s face-processing areas with magnetic pulses, people are unable to with your brain as much as you
recognize faces. see with your eyes.

They will, however, be able to recognize houses, because the brain’s face-perception
occurs separately from its object-perception (McKone et al., 2007; Pitcher et al., 2007).
Thus, functional MRI (fMRI) scans show different brain areas activating when people

1/21/14 9:33 AM MyersAP_SE_2e_Mod18_B.indd 175 1/21/14 9:33 AM

Vision Module 18 175

MyersPsyAP_TE_2e_U04.indd 175 2/20/14 10:43 AM

176 U n i t I V Sensation and Perception

Figure 18.7
Face recognition processing In social
animals such as humans, a dedicated brain
system (shown here in a right-facing brain)
assigns considerable neural bandwidth to the
crucial task of face recognition.

Face recognition area

Figure 18.8 view varied objects (Downing et al., 2001). Brain activity is so
specific (FIGURE 18.8) that, with the help of brain scans, “we
The telltale brain Looking at faces, can tell if a person is looking at a shoe, a chair, or a face, based on the pattern of their brain
houses, and chairs activates different activity,” noted one researcher (Haxby, 2001).
brain areas in this right-facing brain. Research shows that for biologically important objects and events, monkey brains (and
surely ours as well) have a “vast visual encyclopedia” distributed as specialized cells (Perrett
et al., 1988, 1992, 1994). These cells respond to one type of stimulus, such as a specific gaze,
head angle, posture, or body movement. Other supercell clusters integrate this information
and fire only when the cues collectively indicate the direction of someone’s attention and
approach. This instant analysis, which aided our ancestors’survival, also helps a soccer goal-
keeper anticipate the direction of an impending kick, and a driver anticipate a pedestrian’s
next movement.

FIFA via Getty Images

Well-developed supercells
In this 2011 World Cup match,
USA’s Abby Wambach instantly
processed visual information
about the positions and
movements of Brazil’s defenders
and goalkeeper and somehow
managed to get the ball around
them all and into the net.

TEACH parallel processing the Parallel Processing
processing of many aspects of
Concept Connections a problem simultaneously; the Our brain achieves these and other remarkable feats by means of parallel processing: do-
brain’s natural mode of information ing many things at once. To analyze a visual scene, the brain divides it into subdimensions—
Remind students that the human brain processing for many functions, motion, form, depth, color—and works on each aspect simultaneously (Livingstone & Hubel,
is uniquely capable of parallel process- including vision. Contrasts with the 1988). We then construct our perceptions by integrating the separate but parallel work of these
ing, as discussed in Unit III. Computers step-by-step (serial) processing of different visual teams (FIGURE 18.9).
process serially, only able to do one most computers and of conscious
process at a time. Humans can process problem solving.
multiple types of stimuli from the
environment, making us more efficient MyersAP_SE_2e_Mod18_B.indd 176 1/21/14 9:33 AM MyersAP_SE_2e
in understanding the world than com-
puters. In fact, our visual system is so
adept at parallel processing and, thus,
so complicated, that no computer has
been invented that can re-create it.

176 Unit IV Sensation and Perception 2/20/14 8:10 AM

MyersPsyAP_TE_2e_U04.indd 176

Vision Module 18 177

Motion Form Depth Color Figure 18.9 ENGAGE

Parallel processing Studies of Enrichment
patients with brain damage suggest that
the brain delegates the work of processing Those with blindsight, argues Anthony
motion, form, depth, and color to different Marcel of Cambridge University, have
areas. After taking a scene apart, the brain superb vision but they don’t know
integrates these subdimensions into the they can see. Employing a high-speed
perceived image. How does the brain do camera, Marcel tracked the arms,
this? The answer to this question is the hands, and fingers of individuals with
Holy Grail of vision research. blindsight as they reached for objects
they could not consciously see. The
To recognize a face, your brain integrates information projected by your retinas to sev- “I am . . . wonderfully made.” films indicate that their reach was quite
eral visual cortex areas, compares it with stored information, and enables you to recognize -KING DAVID, PSALM 139:14 precise. This suggests that their vision
the face: Grandmother! Scientists are debating whether this stored information is contained remains intact; only the neural areas
in a single cell or distributed over a network. Some supercells—“grandmother cells”—do that bring vision into awareness are
appear to respond very selectively to 1 or 2 faces in 100 (Bowers, 2009). The whole facial impaired.
recognition process requires tremendous brain power—30 percent of the cortex (10 times
the brain area devoted to hearing). ENGAGE

Destroy or disable a neural workstation for a visual subtask, and something peculiar Online Activities
results, as happened to “Mrs. M.” (Hoffman, 1998). Since a stroke damaged areas near the
rear of both sides of her brain, she has been unable to perceive movement. People in a room Blindsight occurs when people experi-
seem “suddenly here or there but I have not seen them moving.” Pouring tea into a cup is a ence damage to the visual cortex of the
challenge because the fluid appears frozen—she cannot perceive it rising in the cup. brain. Their eyes are fully functioning,
but they report they cannot see even
After stroke or surgery damage to the brain’s visual cortex, others have experienced blind- when they demonstrate that they can.
sight (a phenomenon we met in Module 13). Shown a series of sticks, they report seeing nothing. For an interesting demonstration of
Yet when asked to guess whether the sticks are vertical or horizontal, their visual intuition typi- blindsight, as well as additional descrip-
cally offers the correct response. When told, “You got them all right,” they are astounded. There tion of the phenomenon, have students
is, it seems, a second “mind”—a parallel processing system—operating unseen. These separate visit the Serendip Brain and Behavior
visual systems for perception and action illustrate dual processing—the two-track mind. site at http://serendip.brynmawr.edu/
bb/blindsight.html.
***
Think about the wonders of visual processing. As you look at that tiger in the zoo, informa-
tion enters your eyes, is transduced, and is sent to your brain as millions of neural impulses.
As your brain buzzes with activity, various areas focus on different aspects of the tiger’s im-
age. Finally, in some as yet mysterious way, these separate teams pool their work to produce
a meaningful image, which you compare with previously stored images and recognize: a
crouching tiger (FIGURE 18.10).

Figure 18.10

A simplified summary of visual
information processing

Tom Walker/Getty Images

Scene Retinal processing: Feature detection: Parallel processing: Recognition:
Receptor rods and Brain’s detector cells Brain cell teams Brain interprets the
cones bipolar cells respond to specific process combined constructed image
features—edges, lines, information about based on information
ganglion cells motion, form, from stored images
and angles depth, color

1/21/14 9:33 AM T E AC HMyersAP_SE_2e_Mod18_B.indd 177 1/21/14 9:33 AM

Teaching Tip

Discuss Figure 18.10 to show how much work
goes into processing a simple visual image. The
complexity of this process is still fascinating to
researchers.

Vision Module 18 177

MyersPsyAP_TE_2e_U04.indd 177 2/20/14 10:43 AM

178 U n i t I V Sensation and Perception

TEACH “Only mind has sight and hearing; Think, too, about what is happening as you read this page. The printed squiggles areAnnabella Bluesky/Science Source
all things else are deaf and blind.” transmitted by reflected light rays onto your retina, which triggers a process that sends
TRM Common Pitfalls -EPICHARMUS, FRAGMENTS, 550 B.C.E. formless nerve impulses to several areas of your brain, which integrates the information and
decodes meaning, thus completing the transfer of information across time and space from
Students often ask, “How do I know Young-Helmholtz trichromatic my mind to your mind. That all of this happens instantly, effortlessly, and continuously is
I am seeing the same color as some- (three-color) theory the theory indeed awesome. As Roger Sperry (1985) observed, the “insights of science give added, not
one else?” The answer is simple: The that the retina contains three lessened, reasons for awe, respect, and reverence.”
wavelength of light determines the different color receptors—one most
color, so in a properly functioning eye sensitive to red, one to green, one Color Vision
and brain, the color will be processed to blue—which, when stimulated
the same. However, what we call color in combination, can produce the 18-3 What theories help us understand color vision?
shades can vary significantly, espe- perception of any color.
cially in advertising. Acquire several We talk as though objects possess color: “A tomato is red.” Perhaps you have pondered the
catalogues of clothing companies Figure 18.11 old question, “If a tree falls in the forest and no one hears it, does it make a sound?” We can
or go to their websites and compare Color-deficient ask the same of color: If no one sees the tomato, is it red?
what they call similar hues of color for vision People who suffer
clothes they sell. Are forest and hunter red-green deficiency have The answer is No. First, the tomato is everything but red, because it rejects (reflects) the
the same shade of green? Students can trouble perceiving the number long wavelengths of red. Second, the tomato’s color is our mental construction. As Isaac New-
also make a list of the different names within the design. ton (1704) noted, “The [light] rays are not colored.” Color, like all aspects of vision, resides not
for hues in the same color family (reds, in the object but in the theater of our brain, as evidenced by our dreaming in color.
blues, greens, browns, etc.). Use Stu-
dent Activity: Subjective Colors from One of vision’s most basic and intriguing mysteries is how we see the world in color.
the TRM to demonstrate color vision How, from the light energy striking the retina, does the brain manufacture our experience
illusions. of color—and of such a multitude of colors? Our difference threshold for colors is so low
that we can discriminate more than 1 million different color variations (Neitz et al., 2001).
TEACH At least most of us can. For about 1 person in 50, vision is color deficient—and that person
is usually male, because the defect is genetically sex-linked.
Common Pitfalls
Why is some people’s vision deficient? To answer that question, we need to under-
Students have a hard time accepting stand how normal color vision works. Modern detective work on this mystery began
that both theories of color vision are in the nineteenth century, when Hermann von Helmholtz built on the insights of an
likely correct. Because visual process- English physicist, Thomas Young. Knowing that any color can be created by combining
ing occurs in both the eye and the the light waves of three primary colors—red, green, and blue—Young and von Helm-
brain, both theories of color vision holtz inferred that the eye must have three corresponding types of color receptors.Years
may work in each context. However, later, researchers measured the response of various cones to different color stimuli and
testing these theories in humans is not confirmed the Young-Helmholtz trichromatic (three-color) theory, which implies
currently possible, because we do not that the receptors do their color magic in teams of three. Indeed, the retina has three
possess the technology to study the types of color receptors, each especially sensitive to one of three colors. And those col-
retina in action.
ors are, in fact, red, green, and blue. When we stimu-
ENGAGE late combinations of these cones, we see other colors.
For example, there are no receptors especially sensitive
TRM Enrichment to yellow. We see yellow when mixing red and green
light, which stimulates both red-sensitive and green-
People who are color blind see the sensitive cones.
color they are deficient in as a shade
of muted gray or brown. They’ve been Most people with color-deficient vision are not ac-
trained, however, to identify that tually “colorblind.” They simply lack functioning red- or
muted “color” as red, blue, or green green-sensitive cones, or sometimes both. Their vision—
(depending on their deficiency), so perhaps unknown to them, because their lifelong vision
unless tested, they usually do not seems normal—is monochromatic (one-color) or dichro-
know they are color blind! Use Student matic (two-color) instead of trichromatic, making it im-
Activity: The Color Vision Screening possible to distinguish the red and green in FIGURE
Inventory and Color Blindness from 18.11 (Boynton, 1979). Dogs, too, lack receptors for the
the TRM to assess color blindness wavelengths of red, giving them only limited, dichromat-
in students. ic color vision (Neitz et al., 1989).

E N G AG EMyersAP_SE_2e_Mod18_B.indd 178 TEACH 1/23/14 1:57 PM MyersAP_SE_2e

Online Activities Interdisciplinary Connections

Have students experience color blindness by Team teach a lesson in subtractive and additive
accessing the following websites: color mixing with your school’s art teacher.
᭹ www.neitzvision.com/content/ Encourage students to combine colors in
different levels to create some of the 7 million
colorblindworld.html. different hues the human eye can see.
᭹ www.etre.com/tools/colourblindsimulator/.
᭹ www.colourblindawareness.org/colour-

blindness/colour-blindness-experience-it/.

178 Unit IV Sensation and Perception 2/20/14 8:10 AM

MyersPsyAP_TE_2e_U04.indd 178

Vision Module 18 179

Figure 18.12 ENGAGE

Afterimage effect Stare at the TRM Online Activities
center of the flag for a minute and
then shift your eyes to the dot in Afterimages are not limited to color
the white space beside it. What do vision. Students can see afterimages of
you see? (After tiring your neural movement as well. For a vivid example
response to black, green, and yellow, of movement aftereffects, invite stu-
you should see their opponent dents to visit http://dogfeathers.com/
colors.) Stare at a white wall and note java/spirals.html. They will view the
how the size of the flag grows with Counter-Rotating Spirals illusion and
the projection distance. learn more of the history of motion
aftereffects. Use Teacher Demonstra-
But how is it that people blind to red and green can often still see yellow? And why does opponent-process theory tion: Movement Aftereffects from
yellow appear to be a pure color and not a mixture of red and green, the way purple is of red the theory that opposing retinal the TRM for another example to use
and blue? As Ewald Hering soon noted, trichromatic theory leaves some parts of the color processes (red-green, yellow-blue, with students.
vision mystery unsolved. white-black) enable color vision. For
example, some cells are stimulated TEACH
Hering, a physiologist, found a clue in afterimages. Stare at a green square for a while by green and inhibited by red;
and then look at a white sheet of paper, and you will see red, green’s opponent color. Stare at others are stimulated by red and Concept Connections
a yellow square and its opponent color, blue, will appear on the white paper. (To experience inhibited by green.
this, try the flag demonstration in FIGURE 18.12.) Hering surmised that there must be two Opponent processes occur in many
additional color processes, one responsible for red-versus-green perception, and one for different contexts. Here, in Unit IV, the
blue-versus-yellow. perception of color operates as an
opponent process as one color works
Indeed, a century later, researchers also confirmed Hering’s opponent-process theory. only when the other color does not. In
Three sets of opponent retinal processes—red-green, yellow-blue, and white-black—enable col- Unit III, the sympathetic and parasym-
or vision. In the retina and in the thalamus (where impulses from the retina are relayed en pathetic nervous systems work as an
route to the visual cortex), some neurons are turned “on” by red but turned “off” by green. opponent process. When one system is
Others are turned on by green but off by red (DeValois & DeValois, 1975). Like red and green active, the other is not.
marbles sent down a narrow tube, “red” and “green” messages cannot both travel at once. So
we do not experience a reddish green. (Red and green are thus opponents.) But red and blue CLOSE & ASSESS
travel in separate channels, so we can see a reddish-blue magenta.
Exit Assessment
So how do we explain afterimages, such as in the flag demonstration? By staring at
green, we tire our green response. When we then stare at white (which contains all colors, Provide students with a diagram of
including red), only the red part of the green-red pairing will fire normally. the eye (such as Figure 18. 3) and have
them label the diagram with the cor-
The present solution to the mystery of color vision is therefore roughly this: Color pro- rect parts of the eye. Also have them
cessing occurs in two stages. The retina’s red, green, and blue cones respond in varying explain the function of each part,
degrees to different color stimuli, as the Young-Helmholtz trichromatic theory suggested. making sure students know how light
Their signals are then processed by the nervous system’s opponent-process cells, as Her- is received by the eye and transferred
ing’s theory proposed. to the brain for processing.

Before You Move On

᭤ ASK YOURSELF

If you were forced to give up one sense, which would it be? Why?

᭤ TEST YOURSELF

What is the rapid sequence of events that occurs when you see and recognize a friend?
Answers to the Test Yourself questions can be found in Appendix E at the end of the book.

1/23/14 1:57 PM MyersAP_SE_2e_Mod18_B.indd 179 1/21/14 9:33 AM

Vision Module 18 179

MyersPsyAP_TE_2e_U04.indd 179 2/20/14 10:43 AM

180 U n i t I V Sensation and Perception

Module 18 Review 18-3 What theories help us understand color
vision?
18-1 What is the energy that we see as visible
light, and how does the eye transform light • The Young-Helmholtz trichromatic (three-color) theory
energy into neural messages?
proposed that the retina contains three types of color
• The hue we perceive in light depends on its wavelength, receptors. Contemporary research has found three types
of cones, each most sensitive to the wavelengths of one of
and its brightness depends on its intensity. the three primary colors of light (red, green, or blue).

• After entering the eye and being focused by the lens, light • Hering’s opponent-process theory proposed three additional

energy particles (from a thin slice of the broad spectrum of color processes (red-versus-green, blue-versus-yellow,
electromagnetic energy) strike the eye’s inner surface, the black-versus-white). Contemporary research has
retina. The retina’s light-sensitive rods and color-sensitive confirmed that, en route to the brain, neurons in the retina
cones convert the light energy into neural impulses. and the thalamus code the color-related information from
the cones into pairs of opponent colors.
18-2 How do the eye and the brain process
visual information? • These two theories, and the research supporting them,

• After processing by bipolar and ganglion cells in the eyes’ show that color processing occurs in two stages.

retina, neural impulses travel through the optic nerve, to
the thalamus, and on to the visual cortex. In the visual
cortex, feature detectors respond to specific features of the
visual stimulus. Supercell clusters in other critical brain
areas respond to more complex patterns.

• Through parallel processing, the brain handles many

aspects of vision (color, movement, form, and depth)
simultaneously. Other neural teams integrate the results,
comparing them with stored information and enabling
perceptions.

Answers to Multiple-Choice Multiple-Choice Questions
Questions
1. Light’s is the distance from one wave peak to 3. Which of the following explains reversed-color
1. b 3. c afterimages?
2. d 4. b the next. This dimension determines the we
a. Young-Helmholtz trichromatic theory
experience. b. The blind spot
c. Hering’s opponent-process theory
a. hue; wavelength d. Feature detectors
b. wavelength; hue e. Parallel processing
c. hue; intensity
d. wavelength; intensity 4. Your best friend decides to paint her room an extremely
e. intensity; wavelength bright electric blue. Which of the following best fits the
physical properties of the color’s light waves?
2. What do we call the specialized neurons in the occipital
lobe’s visual cortex that respond to particular edges, a. No wavelength; large amplitude
lines, angles, and movements? b. Short wavelength; large amplitude
c. Short wavelength; small amplitude
a. Rods d. Long wavelength; large amplitude
b. Cones e. No wavelength; small amplitude
c. Foveas
d. Feature detectors
e. Ganglion cells

MyersAP_SE_2e_Mod18_B.indd 180 1/21/14 9:33 AM MyersAP_SE_2e

180 Unit IV Sensation and Perception 2/20/14 8:10 AM

MyersPsyAP_TE_2e_U04.indd 180

Vision Module 18 181

5. What do we call the transparent, protective layer that 5. c
light passes through as it enters the eye?
Answer to Practice FRQ 2
a. Pupil
b. Iris 1 point: The Young–Helmholtz
c. Cornea trichromatic theory states that we have
d. Lens 3 color receptors within the eye: red,
e. Fovea green, and blue.
1 point: The opponent process theory
Practice FRQs 2. Explain two theories of color vision in humans. How says that retinal processes only occur in
does one of them explain color deficiency? 3 sets of opponents: red/green, yellow/
1. As light reflected off an object reaches your eye, it passes blue, and white/black.
through several structures before it reaches the retina. (3 points) 1 point: You can explain color defi-
Describe three of these structures, including the function ciency as a dysfunction of red- or
of each. green-sensitive cones (trichromatic
theory) or as a problem with the red–
Answer green opponent processes (opponent
process theory).
1 point: The cornea is at the front of the eye. It bends and
focuses the light waves.

1 point: The pupil is the opening through which light enters
the eyeball. It is surrounded by the iris, which can expand or
contract to allow more or less light to pass through the pupil.

1 point: The lens is the transparent structure behind the
pupil that changes shape to help focus images on the retina.

1/21/14 9:33 AM MyersAP_SE_2e_Mod18_B.indd 181 1/21/14 9:33 AM

Vision Module 18 181

MyersPsyAP_TE_2e_U04.indd 181 2/20/14 10:43 AM

TEACH 182 U n i t I V Sensation and Perception
TRM Discussion Starter
Module 19
Use the Module 19 Fact or Falsehood?
student activity from the TRM to intro- Visual Organization and Interpretation
duce the concepts from this module.
Module Learning Objectives
TEACH
Common Pitfalls 19-1 Describe Gestalt psychologists’ understanding of perceptual
organization, and explain how figure-ground and grouping
Students may not understand the principles contribute to our perceptions.
Gestalt psychologists’ view that the
whole is greater than the sum of its 19-2 Explain how we use binocular and monocular cues to
parts. Have them imagine how much perceive the world in three dimensions and perceive motion.
the different elements that make
up the human body are worth. Even 19-3 Explain how perceptual constancies help us organize our sensations Rob Kavanagh/Alamy
though those elements may be valu- into meaningful perceptions.
able, their combined value making up
the human body is more valuable than 19-4 Describe what research on restored vision, sensory restriction, and
they ever could be on their own. perceptual adaptation reveals about the effects of experience on
perception.
TEACH
Flip It Visual Organization

Students can get some additional help 19-1 How did the Gestalt psychologists understand perceptual
understanding gestalt by watching organization, and how do figure-ground and grouping principles
the Flip It Video: Gestalt Psychology on
this topic. contribute to our perceptions?

gestalt an organized whole. It’s one thing to understand how we see shapes and colors. But how do we organize and
Gestalt psychologists emphasized interpret those sights (or sounds or tastes or smells) so that they become meaningful per-
our tendency to integrate pieces of ceptions—a rose in bloom, a familiar face, a sunset?
information into meaningful wholes.
Early in the twentieth century, a group of German psychologists noticed that when
AP® Exam Tip given a cluster of sensations, people tend to organize them into a gestalt, a German word
meaning a “form” or a “whole.” For example, look at FIGURE 19.1. Note that the indi-
The Necker cube is an excellent vidual elements of this figure, called a Necker cube, are really nothing but eight blue circles,
vehicle for understanding the each containing three converging white lines. When we view these elements all together,
distinction between sensation however, we see a cube that sometimes reverses direction. This phenomenon nicely illus-
and perception. The only visual trates a favorite saying of Gestalt psychologists: In perception, the whole may exceed the
stimuli are the blue wedges. The sum of its parts. If we combine sodium (a corrosive metal) with chlorine (a poisonous gas),
circles, lines, and cube are all the something very different emerges—table salt. Likewise, a unique perceived form emerges
products of perception—they are from a stimulus’ components (Rock & Palmer, 1990).
in your mind and not on the page.
Over the years, the Gestalt psychologists demonstrated many principles we use to or-
ganize our sensations into perceptions. Underlying all of them is a fundamental truth: Our
brain does more than register information about the world. Perception is not just opening a
shutter and letting a picture print itself on the brain. We filter incoming information and
construct perceptions. Mind matters.

MyersAP_SE_2e_Mod19_B.indd 182 1/21/14 9:33 AM MyersAP_SE_2e

182 Unit IV Sensation and Perception 2/20/14 8:10 AM

MyersPsyAP_TE_2e_U04.indd 182

Visual Organization and Interpretation Module 19 183

Figure 19.1 TEACH

A Necker cube What do you see: Teaching Tip
circles with white lines, or a cube? If you
stare at the cube, you may notice that it Have students create their own tessel-
reverses location, moving the tiny X in the lations like the one in Figure 19.2. This
center from the front edge to the back. picture is similar to tessellations cre-
At times, the cube may seem to float in ated by M. C. Escher, whose drawings
front of the page, with circles behind it. capitalized on figure–ground illusions
At other times, the circles may become to create fanciful, yet impossible,
holes in the page through which the pictures. A tessellation is a repeating
cube appears, as though it were floating geometric pattern, and the ones in
behind the page. There is far more to Figure 19.2 and those that Escher
perception than meets the eye. (From created would combine tessellations
Bradley et al., 1976.) with figure–ground illusions where
2 geometric patterns would repeat at
Form Perception Figure 19.2 the same time: 1 as a figure and 1 as
Reversible figure and ground a ground.

Imagine designing a video-computer system that, like your eye-brain system, can recognize ENGAGE

faces at a glance. What abilities would it need? Active Learning

FIGURE AND GROUND figure-ground the organization Students can discover auditory figure–
To start with, the video-computer system would need to separate faces from their backgrounds. of the visual field into objects (the ground illusions by simply repeating
Likewise, in our eye-brain system, our first perceptual task is to perceive any object (the figure) figures) that stand out from their aloud a word such as say. It will shift
as distinct from its surroundings (the ground). Among the voices you hear at a party, the one surroundings (the ground). abruptly to ace and back again to say.
you attend to becomes the figure; all others are part of the ground. As you read, the words are
the figure; the white paper is the ground. Sometimes the same stimulus can trigger more than grouping the perceptual tendency TEACH
one perception. In FIGURE 19.2, the figure-ground relationship continually reverses—but to organize stimuli into coherent
always we organize the stimulus into a figure seen against a ground. groups. Common Pitfalls

GROUPING Students typically find gestalt group-
Having discriminated figure from ground, we (and our video-computer system) must also orga- ing principles to be very mundane and
nize the figure into a meaningful form. Some basic features of a scene—such as color, movement, obvious. Remind students that the
and light-dark contrast—we process instantly and automatically (Treisman, 1987). Our minds Gestalt psychologists were the first to
bring order and form to stimuli by following certain rules for grouping.These rules, identified by study systematically how people per-
the Gestalt psychologists and applied even by infants, illustrate how the perceived whole differs ceive whole objects. Before their work,
from the sum of its parts (Quinn et al., 2002; Rock & Palmer, 1990).Three examples: people took these grouping principles
for granted.
PROXIMITY We group nearby figures together. We see not six separate lines, but three sets of
two lines.

CONTINUITY We perceive smooth, continuous patterns rather than discontinuous ones. This
pattern could be a series of alternating semicircles, but we perceive it as two continuous
lines—one wavy, one straight.

CLOSURE We fill in gaps to create a complete, whole object. Thus we assume that the circles
on the right are complete but partially blocked by the (illusory) triangle. Add nothing more
than little line segments to close off the circles and your brain stops constructing a triangle.
Such principles usually help us construct reality.

Proximity Continuity Closure

1/21/14 9:33 AM T E AC HMyersAP_SE_2e_Mod19_B.indd 183 1/21/14 9:33 AM

Teaching Tip ᭹ Similarity: Items that look the same are
usually grouped together. Have students
Use the following examples of 2 of the gestalt imagine their reactions when someone
grouping principles to help students remem- they do not know well wears the same
ber them: outfit or shirt as they do. Typically, they are
uncomfortable with this because we do not
᭹ Proximity: We perceive items that are like being grouped with people we do not
close to each other as being together. Have know well.
students imagine their reactions when
someone they do not know well walks in Visual Organization and Interpretation Module 19
step with them down the hall. Typically,
people feel discomfort when this happens
because of their proximity to the other
person. We do not like to be grouped
together with people we do not know well.

183

MyersPsyAP_TE_2e_U04.indd 183 2/20/14 8:10 AM

184 U n i t I V Sensation and Perception

TEACH Figure 19.3 Depth Perception
Visual cliff Eleanor Gibson and
Concept Connections Richard Walk devised a miniature 19-2 How do we use binocular and monocular cues to perceive the world
cliff with a glass-covered drop-off to in three dimensions and perceive motion?
Refer students to Unit IX for a thorough determine whether crawling infants
discussion of infant development. can perceive depth. Even when From the two-dimensional images falling on our retinas, we somehow organize three-di-
The visual cliff study, a classic in the coaxed, infants are reluctant to mensional perceptions. Depth perception enables us to estimate an object’s distance from
field, helped demonstrate how infants venture onto the glass over the cliff us. At a glance, we can estimate the distance of an oncoming car or the height of a house.
perceive depth and ways to measure (Gibson & Walk, 1960). Depth perception is partly innate, as Eleanor Gibson and Richard Walk (1960) discovered
infant perceptions without relying on using a model of a cliff with a drop-off area (which was covered by sturdy glass). Gibson’s
language. depth perception the ability inspiration for these visual cliff experiments occurred while she was picnicking on the rim
to see objects in three dimensions of the Grand Canyon. She wondered: Would a toddler peering over the rim perceive the
ENGAGE although the images that strike the dangerous drop-off and draw back?
retina are two-dimensional; allows
TRM Enrichment us to judge distance. Back in their Cornell University lab-
visual cliff a laboratory device for oratory, Gibson and Walk placed 6- to
We are able to perceive depth because testing depth perception in infants 14-month-old infants on the edge of a safe
we have 2 eyes in the front of our and young animals. canyon and had the infants’ mothers coax
heads. Animals with eyes on the binocular cues depth cues, such them to crawl out onto the glass (FIGURE
sides of their heads need that type as retinal disparity, that depend on 19.3). Most infants refused to do so, indicat-
of vision to scan for danger around the use of two eyes. ing that they could perceive depth.
them. Peripheral vision is much bet- retinal disparity a binocular cue
ter at detecting motion, so stronger for perceiving depth: By comparing Had they learned to perceive depth?
peripheral vision through eyes on the images from the retinas in the two Learning seems to be part of the answer
sides of the head gives an evolutionary eyes, the brain computes distance— because crawling, no matter when it be-
advantage to animals that are typically the greater the disparity (difference) gins, seems to increase infants’ wariness of
hunted. Predators do not need to be between the two images, the closer heights (Campos et al., 1992). Yet, the re-
on the look out for danger—they are the object. searchers observed, mobile newborn ani-
the danger! They need to determine mals come prepared to perceive depth. Even
distances between them and their those with virtually no visual experience—
prey, which requires the depth percep- including young kittens, a day-old goat, and newly hatched chicks—will not venture across
tion that binocular vision provides. the visual cliff. Thus, it seems that biology predisposes us to be wary of heights and experi-
Use Student Activity: Binocular Vision ence amplifies that fear.
Versus Monocular Vision from the How do we perceive depth? How do we transform two differing two-dimensional (2-D)
TRM to demonstrate the value of retinal images into a single three-dimensional (3-D) perception? Our brain constructs these
binocular cues. perceptions using information supplied by one or both eyes.

BINOCULAR CUES

Try this: With both eyes open, hold two pens or pencils in front of you and touch their
tips together. Now do so with one eye closed. With one eye, the task becomes noticeably
more difficult, demonstrating the importance of binocular cues in judging the distance of
nearby objects. Two eyes are better than one.

Because your eyes are about 2½ inches apart, your retinas receive slightly different im-
ages of the world. By comparing these two images, your brain can judge how close an object
is to you.The greater the retinal disparity, or difference between the two images, the closer
the object. Try it. Hold your two index fingers, with the tips about half an inch apart, directly
in front of your nose, and your retinas will receive quite different views. If you close one eye
and then the other, you can see the difference. (You may also create a finger sausage, as in
FIGURE 19.4.) At a greater distance—say, when you hold your fingers at arm’s length—the
disparity is smaller.

We could easily build this feature into our video-computer system. Moviemakers
can simulate or exaggerate retinal disparity by filming a scene with two cameras placed
a few inches apart. Viewers then wear glasses that allow the left eye to see only the im-
age from the left camera, and the right eye to see only the image from the right camera.

T E AC HMyersAP_SE_2e_Mod19_B.indd 184 TEACH 1/21/14 9:33 AM MyersAP_SE_2e

Teaching Tip Online Activities

Relate retinal disparity to real life by having Some people cannot see depth well because of
students recall a time when they were lying different conditions that hinder the eyes’ ability
down watching television. Ask them if they to see in stereo. Check out www.vision3d.com
ever had their vision in one eye obscured by to find the answers to the following questions:
a pillow or blanket they were lying with. If so,
then they probably had to shift their position ᭹ What is amblyopia (lazy eye)? What are
to correct the obstruction or close one eye: some treatments for this condition?
watching TV and a pillow at the same time is
not very enjoyable! ᭹ What is strabismus (deflected eye, crossed
eyes, or wall eyes)? What are some
treatments for this condition?

᭹ How are vision problems related to learning
disabilities and dyslexia?

184 Unit IV Sensation and Perception

MyersPsyAP_TE_2e_U04.indd 184 2/20/14 8:10 AM

Visual Organization and Interpretation Module 19 185

FYI ENGAGE

Carnivorous animals, including TRM Active Learning
humans, have eyes that enable
forward focus on a prey and offer Try to round up some Viewmasters
binocular vision-enhanced depth to demonstrate retinal disparity in
perception. Grazing herbivores, class. Students can view the images
such as horses and sheep, typically with 1 eye closed and both eyes open
have eyes on the sides of their to see how the same image is pro-
skull. Although lacking binocular jected in 2 slightly different places to
depth perception, they have capitalize on our perception of depth.
sweeping peripheral vision. Use Student Activity: Autostereograms
from the TRM to demonstrate depth
Figure 19.4 perception using a Magic Eye™-like
activity.
The floating finger sausage Hold
your two index fingers about 5 inches in ENGAGE
front of your eyes, with their tips half an
inch apart. Now look beyond them and Active Learning
note the weird result. Move your fingers
out farther and the retinal disparity—and Have students roll a sheet of paper into
the finger sausage—will shrink. a tube and raise it to their right eye like
a telescope. Tell them to look through
The resulting 3-D effect, as 3-D movie fans know, mimics or exaggerates normal retinal monocular cues depth cues, it, focusing on a blank wall in front
disparity. Similarly, twin cameras in airplanes can take photos of terrain for integration such as interposition and linear of them. Next, have them hold their
into 3-D maps. perspective, available to either eye left hand open beside the tube and
alone. continue to focus ahead. The images
MONOCULAR CUES phi phenomenon an illusion of received by the 2 eyes will fuse, and
movement created when two or the hole in the tube will appear to be
How do we judge whether a person is 10 or 100 meters away? Retinal disparity won’t help more adjacent lights blink on and in the student’s hand. They may need
us here, because there won’t be much difference between the images cast on our right and off in quick succession. to slide the hand alongside the tube
left retinas. At such distances, we depend on monocular cues (depth cues available to until they find the precise spot where
each eye separately). See FIGURE 19.5 on the next page for some examples. “Sometimes I wonder: Why is that the hole appears to go through the
Frisbee getting bigger? And then very center of the palm.
Motion Perception it hits me.” -ANONYMOUS
Fisher, J. (1979). Body magic. New York: Stein
Imagine that you could perceive the world as having color, form, and depth but that you “From there to here, from and Day.
could not see motion. Not only would you be unable to bike or drive, you would have here to there, funny things are
trouble writing, eating, and walking. everywhere.” -DR. SEUSS, ONE FISH, ENGAGE
TWO FISH, RED FISH, BLUE FISH, 1960
Normally your brain computes motion based partly on its assumption that shrinking Online Activities
objects are retreating (not getting smaller) and enlarging objects are approaching. But you
are imperfect at motion perception. Large objects, such as trains, appear to move more In a computer lab or as a homework
slowly than smaller objects, such as cars, moving at the same speed. (Perhaps at an airport assignment, have students try out
you’ve noticed that jumbo jets seem to land more slowly than little jets.) some of the 3D vision games found
in the Optometrists Network at
To catch a fly ball, softball or cricket players (unlike drivers) want to achieve a collision— www.vision3d.com.
with the ball that’s flying their way. To accomplish that, they follow an unconscious rule— ᭹ Eye Hop Game: www.vision3d.com/
one they can’t explain but know intuitively: Run to keep the ball at a constantly increasing
angle of gaze (McBeath et al., 1995). A dog catching a Frisbee does the same (Shaffer et al., ehop.html
2004). ᭹ Framing Game: www.vision3d.com/

The brain also perceives continuous movement in a rapid series of slightly varying im- frame.html
ages (a phenomenon called stroboscopic movement). As film animation artists know well, ᭹ Reversible figures: www.vision3d.
you can create this illusion by flashing 24 still pictures a second. The motion we then see in
popular action adventures is not in the film, which merely presents a superfast slide show. com/optical/puzzles.html
We construct that motion in our heads, just as we construct movement in blinking marquees
and holiday lights. When two adjacent stationary lights blink on and off in quick succession,
we perceive a single light moving back and forth between them. Lighted signs exploit this
phi phenomenon with a succession of lights that creates the impression of, say, a moving
arrow.

1/21/14 9:33 AM E N G AG EMyersAP_SE_2e_Mod19_B.indd 185 ENGAGE 1/21/14 9:33 AM

Active Learning Enrichment

Have students close 1 eye, point their 2 forefin- Although we can see depth with only 1 eye, it
gers toward each other, and then bring them is much more difficult to perceive depth with
together quickly. They are likely to miss. An 1 eye closed than with both eyes open.
even more difficult test is to have them hold Animals with eyes on the sides of their heads
a pencil in each hand and bring the points (birds, rabbits, etc.) tend to compensate for
together. It is important, of course, that their their lack of depth perception by moving their
hands not be at arm’s length. If they repeat heads around a lot to as they try to look around
either test, they ought to drop their arms out of objects. This type of movement, which creates
view before they try again. This will eliminate depth, is called monocular parallax.
the perception of any depth cues from the
position of the hands and arms.

Visual Organization and Interpretation Module 19 185

MyersPsyAP_TE_2e_U04.indd 185 2/20/14 8:10 AM

186 U n i t I V Sensation and Perception

TEACH Image courtesy Shaun P. Vecera, Ph.D., adapted from © Philip Mugridge/Alamy
stimuli that appeared in Vecrera et al., 2002
Common Pitfalls
Relative height We perceive objects Relative size If we assume two Interposition Interpose means “to come
Students may feel that the monocular higher in our field of vision as farther objects are similar in size, most people between.” If one object partially blocks our view
depth cues are more common sense away. Because we assume the lower part perceive the one that casts the smaller of another, we perceive it as closer.
than psychology. Emphasize that with- of a figure-ground illustration is closer, we retinal image as farther away.
out these cues, many forms of enter- perceive it as figure (Vecera et al., 2002).
tainment—from art to television to Invert this illustration and the black will Linear perspective Parallel lines appear to meet in Light and shadow Shading
movies—would lack the visual richness become ground, like a night sky. the distance. The sharper the angle of convergence, the produces a sense of depth
and beauty they possess. Monocular greater the perceived distance. consistent with our assumption
depth cues help make the world a Relative motion As we move, objects that light comes from above. If you
more visually interesting place! that are actually stable may appear to move. ©The New Yorker Collection, 2002, Jack Ziegler from invert this illustration, the hollow will
If while riding on a bus you fix your gaze cartoonbank.com. All Rights Reserved. become a hill.
TEACH on some point—say, a house—the objects
beyond the fixation point will appear to move
Flip It with you. Objects in front of the point will
appear to move backward. The farther an
Students can get some additional object is from the fixation point, the faster it will
help understanding monocular seem to move.
cues by watching the Flip It Video:
Monocular Cues. Fixation
point
TEACH
From “Perceiving Shape From Shading” by
Teaching Tip Vilayanur S. Ramachandran. Copyright ©
1988 by Scientific American, Inc. All Rights
Many of these monocular depth cues
rely on previous knowledge in order Reserved.
to work. If we don’t already know how
large an object is, then the relative Direction of passenger’s motion Perceptual Constancy
size cue becomes meaningless. Here
is where top-down processing is most Figure 19.5 19-3 How do perceptual constancies help us organize our sensations into
useful in helping us accurately under- Monocular depth cues meaningful perceptions?
stand the world. Have students explain
how top-down processing is useful. AP® Exam Tip So far, we have noted that our video-computer system must perceive objects as we do—as
having a distinct form, location, and perhaps motion. Its next task is to recognize objects
TEACH The illustrations in Figure 19.5 without being deceived by changes in their color, brightness, shape, or size—a top-down
provide you with excellent process called perceptual constancy. Regardless of the viewing angle, distance, and il-
Teaching Tip opportunities to practice lumination, we can identify people and things in less time than it takes to draw a breath,
identifying monocular depth a feat that would be a monumental challenge for even advanced computers and that has
Divide students into small groups cues. To really demonstrate your intrigued researchers for decades.
and have them compile a portfolio of understanding, look for these
examples of monocular depth cues. cues in other drawings and
Have them bring in their own maga- photographs. There are almost
zines (or collect back issues from your always cues to identify.
library) to look for examples of each
type of monocular cue, collecting E N G AG EMyersAP_SE_2e_Mod19_B.indd 186 TEACH 1/21/14 9:33 AM MyersAP_SE_2e
them in a scrapbook or poster and
identifying the one that each picture Active Learning Teaching Tip
exemplifies.
Boston’s Museum of Science offers a wonderful Another monocular cue students should know
online lesson in which students can create a is texture gradient. This is the tendency for
realistic and natural picture using linear per- textured surfaces to appear to become smaller
spective. The Leonardo’s Window lesson asks and finer as distance from the viewer increases.
students to tape some acetate onto a window For example, a hiker in a field of flowers will
and trace the lines found in the natural world see the closest flowers clearly, but the details
outside to create a painting. For more instruc- of the flowers become less apparent and seem
tions, see http://legacy.mos.org/sln/Leonardo/ smaller the farther into the distance he looks.
UsingLeosWindow.html.

186 Unit IV Sensation and Perception

MyersPsyAP_TE_2e_U04.indd 186 2/20/14 10:43 AM

Visual Organization and Interpretation Module 19 187

COLOR AND BRIGHTNESS CONSTANCIES perceptual constancy perceiving ENGAGE
objects as unchanging (having
Color does not reside in an object. Our experience of color depends on the object’s context. consistent shapes, size, brightness, Active Learning
If you view an isolated tomato through a paper tube, its color would seem to change as the and color) even as illumination and
light—and thus the wavelengths reflected from its surface—changed. But if you viewed retinal images change. Bring in 2 sets of men’s dress socks
that tomato as one item in a bowl of fresh fruit and vegetables, its color would remain (one dark blue and one black). In dim
roughly constant as the lighting shifts. This perception of consistent color is known as color constancy perceiving light, have students identify the color
color constancy. familiar objects as having consistent of the socks. Do the same in brighter
color, even if changing illumination light. Although the task may be easier
Though we take color constancy for granted, this ability is truly remarkable. A blue alters the wavelengths reflected by in brighter light, it is still not definitive
poker chip under indoor lighting reflects wavelengths that match those reflected by a the object. until both colors of socks are compared
sunlit gold chip (Jameson, 1985). Yet bring a bluebird indoors and it won’t look like a to each other. Sometimes blue and
goldfinch. The color is not in the bird’s feathers. You and I see color thanks to our brain’s black are difficult to distinguish in dim
computations of the light reflected by an object relative to the objects surrounding it. (But light, which is why getting dressed in
only if we grew up with normal light, it seems. Monkeys raised under a restricted range the dark can often bring about mis-
of wavelengths later have great difficulty recognizing the same color when illumination matches when choosing dark socks or
varies [Sugita, 2004].) FIGURE 19.6 dramatically illustrates the ability of a blue object to shoes to wear!
appear very different in three different contexts.Yet we have no trouble seeing these disks
as blue. TEACH

R. Beau Lotto at University College, London Figure 19.6 Teaching Tip

Color depends on context Cite an interesting example of depth
(a) Believe it or not, these three blue cues working to create an illusion of
disks are identical in color. reality by discussing the proportions
(b) Remove the surrounding context of Michelangelo’s sculpture, The Pieta.
and see what results. The Pieta depicts the Virgin Mary hold-
ing her dead son Jesus. Although the
(a) (b) figure of Christ is lifelike and propor-
tional to reality, if the figure of Mary
Similarly, brightness constancy (also called lightness constancy) depends on context. We were to rise to her feet and stand erect,
perceive an object as having a constant brightness even while its illumination varies. This she would be over 7’ tall! But to look at
perception of constancy depends on relative luminance—the amount of light an object re- the sculpture, one would never notice
flects relative to its surroundings (FIGURE 19.7 on the next page). White paper reflects 90 Mary was so much larger than her son
percent of the light falling on it; black paper, only 10 percent. Although a black paper viewed in reality.
in sunlight may reflect 100 times more light than does a white paper viewed indoors, it will
still look black (McBurney & Collings, 1984). But if you view sunlit black paper through a
narrow tube so nothing else is visible, it may look gray, because in bright sunshine it reflects
a fair amount of light.View it without the tube and it is again black, because it reflects much
less light than the objects around it.

This principle—that we perceive objects not in isolation but in their environmental con-
text—matters to artists, interior decorators, and clothing designers. Our perception of the
color and brightness of a wall or of a streak of paint on a canvas is determined not just by the
paint in the can but by the surrounding colors. The take-home lesson: Comparisons govern
our perceptions.

1/21/14 9:33 AM MyersAP_SE_2e_Mod19_B.indd 187 1/21/14 9:33 AM

Visual Organization and Interpretation Module 19 187

MyersPsyAP_TE_2e_U04.indd 187 2/20/14 8:10 AM

188 U n i t I V Sensation and Perception

TEACH Figure 19.7

Teaching Tip Relative luminance Squares A
and B are identical in color, believe
Have students imagine how disturb- it or not. (If you don’t believe me,
ing the world would be if we suddenly photocopy the illustration, cut out
lost our ability to perceive constancy. the squares, and compare.) But we
What if objects appeared to change perceive A as lighter, thanks to its
shape when they moved? What if color surrounding context.
became different in different levels
of light? “My monster little brother” A
would take on a whole new meaning B
if he grew and changed shapes and
colors right before your eyes! SHAPE AND SIZE CONSTANCIES

ENGAGE Sometimes an object whose actual shape cannot change seems to change shape with the
angle of our view (FIGURE 19.8). More often, thanks to shape constancy, we perceive the
Active Learning form of familiar objects, such as the door in FIGURE 19.9, as constant even while our reti-
nas receive changing images of them. Our brain manages this feat thanks to visual cortex
The importance of perceptual con- neurons that rapidly learn to associate different views of an object (Li & DiCarlo, 2008).
stancy is demonstrated in the follow-
ing passage: Thanks to size constancy, we perceive objects as having a constant size, even while our
distance from them varies. We assume a car is large enough to carry people, even when we
I cdnuolt blveiee taht I cluod aulaclty see its tiny image from two blocks away. This assumption also illustrates the close connec-
uesdnatnrd waht I was rdanieg. Takhns tion between perceived distance and perceived size. Perceiving an object’s distance gives us
to the phaonmneal pweor of the cues to its size. Likewise, knowing its general size—that the object is a car—provides us
hmuan mnid, aoccdrnig to rscheearch with cues to its distance.
at Cmabrigde Uinervtisy, it deosn’t
mttaer in waht oredr the ltteers in a Figure 19.8 Figure 19.9
wrod are, the olny iprmoatnt tihng is
taht the frist and lsat ltteer be in the Perceiving shape Do the tops of these Shape constancy A door casts an
rghit pclae. The rset can be a taotl tables have different dimensions? They appear increasingly trapezoidal image on our
mses and you can sitll raed it wouthit to. But—believe it or not—they are identical. retinas as it opens, yet we still perceive it
a porbelm. Tihs is bcuseae the huamn (Measure and see.) With both tables, we adjust as rectangular.
mnid deos not raed ervey lteter by istlef, our perceptions relative to our viewing angle.
but the wrod as a wlohe. Amzanig, huh?
Yaeh and I awlyas tghuhot slpeling MyersAP_SE_2e_Mod19_B.indd 188 1/21/14 9:33 AM MyersAP_SE_2e
was ipmorantt! if you can raed tihs,
psas it on!!

While this popular Internet message
was not really based on a study by
Cambridge University, and its scientific
validity is in serious doubt, the fact that
people can still decipher this para-
graph is testimony to the power of the
brain to make sense out of nonsense.
Have students discuss ways to test the
claims of this passage scientifically.

188 Unit IV Sensation and Perception 2/20/14 8:10 AM

MyersPsyAP_TE_2e_U04.indd 188

Visual Organization and Interpretation Module 19 189

Even in size-distance judgments, however, we consider an object’s context. The dogs in Figure 19.10 ENGAGE
Module 17’s Figure 17.3 cast identical images on our retinas. Using linear perspective as a
cue (see Figure 19.5), our brain assumes that the pursuing dog is farther away. We therefore The illusion of the shrinking TRM Enrichment
perceive it as larger. It isn’t. and growing girls This
distorted room, designed by When Spanish conquistadors explored
This interplay between perceived size and perceived distance helps explain several Adelbert Ames, appears to have the southwestern United States, their
well-known illusions, including the Moon illusion: The Moon looks up to 50 percent larger a normal rectangular shape when perception was tricked as they looked
when near the horizon than when high in the sky. Can you imagine why? For at least 22 viewed through a peephole with down on the Colorado River from the
centuries, scholars have debated this question (Hershenson, 1989). One reason is that one eye. The girl in the right corner rim of the Grand Canyon. What they
cues to objects’ distances make the horizon Moon—like the distant dog in Figure 17.3— appears disproportionately large perceived to be a small running creek
appear farther away. If it’s farther away, our brain assumes, it must be larger than the because we judge her size based about 6’ wide was actually a raging
Moon high in the night sky (Kaufman & Kaufman, 2000). Take away the distance cue, by on the false assumption that she is river over a mile wide! The perceptual
looking at the horizon Moon (or each dog) through a paper tube, and the object will im- the same distance away as the girl cues from the top of the canyon fooled
mediately shrink. in the left corner. them into thinking the river was much
smaller than it really was. Use Student
Size-distance relationships also explain why in FIGURE 19.10 the two same-age girls Activity: Perceived Lunar Size from the
seem so different in size. As the diagram reveals, the girls are actually about the same size, TRM to demonstrate this phenomenon.
but the room is distorted. Viewed with one eye through a peephole, the room’s trapezoidal
walls produce the same images you would see in a normal rectangular room viewed with ENGAGE
both eyes. Presented with the camera’s one-eyed view, your brain makes the reasonable
assumption that the room is normal and each girl is therefore the same distance from you. Active Learning
Given the different sizes of the girls’ images on your retinas, your brain ends up calculating
that the girls must be very different in size. Have students hold a hand in front of
their face at arm’s length and move
Perceptual illusions reinforce a fundamental lesson: Perception is not merely a projec- it toward their head, then away; they
tion of the world onto our brain. Rather, our sensations are disassembled into information will perceive no change in size. The
bits that our brain, using both bottom-up and top-down processing, then reassembles into size of the retinal image is, of course,
its own functional model of the external world. During this reassembly process, our as- changing. Now, have students hold
sumptions—such as the usual relationship between distance and size—can lead us astray. the forefinger of their left hand about
Our brain constructs our perceptions. 8" in front of their face and focus on
it. They should then position their
*** right hand at arm’s length, past their
Form perception, depth perception, motion perception, and perceptual constancies illumi- left forefinger. While maintaining
nate how we organize our visual experiences. Perceptual organization applies to our other fixation on their left fingertip, they
senses, too. It explains why we perceive a clock’s steady tick not as a tick-tick-tick-tick but should move their right hand toward
as grouped sounds, say, TICK-tick, TICK-tick. Listening to an unfamiliar language, we have and away from their face. Although
trouble hearing where one word stops and the next one begins. Listening to our own lan- their focus should be on the finger,
guage, we automatically hear distinct words. This, too, reflects perceptual organization. But they should also notice the image of
it is more, for we even organize a string of letters—THEDOGATEMEAT—into words that the hand as it moves. It will change
make an intelligible phrase, more likely “The dog ate meat” than “The do gate me at” dramatically in size.
(McBurney & Collings, 1984). This process involves not only the organization we’ve been
discussing, but also interpretation—discerning meaning in what we perceive.

S. Schwartzenberg/The Exploratorium

1/21/14 9:33 AM MyersAP_SE_2e_Mod19_B.indd 189 1/21/14 9:33 AM

Visual Organization and Interpretation Module 19 189

MyersPsyAP_TE_2e_U04.indd 189 2/20/14 8:11 AM

190 U n i t I V Sensation and Perception

“Let us then suppose the mind to Visual Interpretation
be, as we say, white paper void of
all characters, without any ideas: Philosophers have debated whether our perceptual abilities should be credited to our nature
How comes it to be furnished? or our nurture.To what extent do we learn to perceive? German philosopher Immanuel Kant
. . . To this I answer, in one word, (1724–1804) maintained that knowledge comes from our inborn ways of organizing sensory
from EXPERIENCE.” -JOHN LOCKE, experiences. Indeed, we come equipped to process sensory information. But British philoso-
AN ESSAY CONCERNING HUMAN pher John Locke (1632–1704) argued that through our experiences we also learn to perceive
UNDERSTANDING, 1690 the world. Indeed, we learn to link an object’s distance with its size. So, just how important
is experience? How radically does it shape our perceptual interpretations?

Experience and Visual Perception

19-4 What does research on restored vision, sensory restriction, and
perceptual adaptation reveal about the effects of experience on
perception?

TEACH Learning to see: At age 3, Mike RESTORED VISION AND SENSORY RESTRICTION
May lost his vision in an explosion.
Concept Connections Decades later, after a new cornea Writing to John Locke, William Molyneux wondered whether “a man born blind, and now
restored vision to his right eye, he got adult, taught by his touch to distinguish between a cube and a sphere” could, if made to see,
Critical periods are discussed here as his first look at his wife and children. visually distinguish the two. Locke’s answer was No, because the man would never have
well as in Units VII and IX. Be sure to Alas, although signals were now learned to see the difference.
help students connect this discussion reaching his visual cortex, it lacked
with the later ones. the experience to interpret them. May Molyneux’s hypothetical case has since been put to the test with a few dozen adults
could not recognize expressions, or who, though blind from birth, have gained sight (Gregory, 1978; von Senden, 1932). Most
ENGAGE faces, apart from features such as hair. had been born with cataracts—clouded lenses that allowed them to see only diffused light,
Yet he can see an object in motion rather as someone might see a foggy image through a Ping-Pong ball sliced in half. After
TRM Enrichment and has learned to navigate his world cataract surgery, the patients could distinguish figure from ground and could sense colors—
and to marvel at such things as dust suggesting that these aspects of perception are innate. But much as Locke supposed, they
Myers describes experiments in which floating in sunlight (Abrams, 2002). often could not visually recognize objects that were familiar by touch.
infant animals were outfitted with
goggles through which they could Seeking to gain more control than is provided by clinical cases, researchers have outfit-
only see diffuse, unpatterned light. ted infant kittens and monkeys with goggles through which they could see only diffuse, un-
Use of this type of apparatus is called patterned light (Wiesel, 1982). After infancy, when the goggles were removed, these animals
a Ganzfeld procedure. This procedure exhibited perceptual limitations much like those of humans born with cataracts. They could
is often used to create an experience distinguish color and brightness, but not the form of a circle from that of a square. Their
of sensory deprivation. Use Student eyes had not degenerated; their retinas still relayed signals to their visual cortex. But lack-
Activity: The Ganzfeld from the TRM to ing stimulation, the cortical cells had not developed normal connections. Thus, the animals
demonstrate how the elimination of remained functionally blind to shape. Experience guides, sustains, and maintains the brain’s
contours effectively eliminates visual
perception. neural organization as it forms the pathways that affect our perceptions.
In both humans and animals, similar sensory restrictions later in life do no
AP Photo/Marcio Jose Sanchez
permanent harm. When researchers cover the eye of an adult animal for several
months, its vision will be unaffected after the eye patch is removed. When surgeons
remove cataracts that develop during late adulthood, most people are thrilled at
the return to normal vision.

The effect of sensory restriction on infant cats, monkeys, and humans sug-
gests there is a critical period for normal sensory and perceptual development.
Nurture sculpts what nature has endowed. In less dramatic ways, it continues to
do so throughout our lives. Despite concerns about their social costs (more on
this in Module 78), action video games sharpen spatial skills such as visual at-
tention, eye-hand coordination and speed, and tracking multiple objects (Spence
& Feng, 2010).

Experiments on early sensory deprivation provide a partial answer to the en-
during question about experience: Does the effect of early experience last a life-
time? For some aspects of perception, the answer is clearly Yes: “Use it soon or lose
it.” We retain the imprint of some early sensory experiences far into the future.

MyersAP_SE_2e_Mod19_B.indd 190 1/21/14 9:33 AM MyersAP_SE_2e

190 Unit IV Sensation and Perception 2/20/14 8:11 AM

MyersPsyAP_TE_2e_U04.indd 190

Visual Organization and Interpretation Module 19 191

PERCEPTUAL ADAPTATION perceptual adaptation in Courtesy of Hubert Dolezal ENGAGE
vision, the ability to adjust to
Given a new pair of glasses, we may feel slightly disoriented, even dizzy. Within a day or an artificially displaced or even TRM Active Learning
two, we adjust. Our perceptual adaptation to changed visual input makes the world seem inverted visual field.
normal again. But imagine a far more dramatic new pair of glasses—one that shifts the ap- Create or purchase visual distortion
parent location of objects 40 degrees to the left. When you first put them on and toss a ball Perceptual adaptation “Oops, goggles for students to use in class.
to a friend, it sails off to the left. Walking forward to shake hands with the person, you veer missed,” thought researcher Hubert (You can purchase goggles from
to the left. Dolezal as he viewed the world through www.psychkits.com). Have students
inverting goggles. Yet, believe it or not, toss soft balls to each other as they
Could you adapt to this distorted world? Baby chicks cannot. When fitted with such kittens, monkeys, and humans can wear the goggles. After a few tries, they
lenses, they continue to peck where food grains seem to be (Hess, 1956; Rossi, 1968). But we adapt to an inverted world. will find they can throw accurately.
humans adapt to distorting lenses quickly. Within a few minutes your throws would Then have them take off the goggles.
again be accurate, your stride on target. Remove the lenses and you would experi- They will need a few more tries to
ence an aftereffect: At first your throws would err in the opposite direction, sailing off throw accurately again because their
to the right; but again, within minutes you would readapt. vision will be distorted in the opposite
way from what it was while they were
Indeed, given an even more radical pair of glasses—one that literally turns the wearing the goggles. Use Student
world upside down—you could still adapt. Psychologist George Stratton (1896) ex- Activity: Displacement Goggles from
perienced this when he invented, and for eight days wore, optical headgear that the TRM for a tutorial on how to create
flipped left to right and up to down, making him the first person to experience a displacement goggles.
right-side-up retinal image while standing upright. The ground was up, the sky was
down. CLOSE & ASSESS

At first, when Stratton wanted to walk, he found himself searching for his feet, Exit Assessment
which were now “up.” Eating was nearly impossible. He became nauseated and de-
pressed. But he persisted, and by the eighth day he could comfortably reach for an Many of the concepts in this module
object in the right direction and walk without bumping into things. When Stratton are confusing or unfamiliar to stu-
finally removed the headgear, he readapted quickly. dents. Choose 2–4 concepts and have
students write a short explanation of
In later experiments, people wearing the optical gear have even been able to the concept as if they were explaining
ride a motorcycle, ski the Alps, and fly an airplane (Dolezal, 1982; Kohler, 1962). it to an elementary student. This will
The world around them still seemed above their heads or on the wrong side. But by help you see if students understand
actively moving about in these topsy-turvy worlds, they adapted to the context and the material well enough to explain it
learned to coordinate their movements. simply and concisely.

Before You Move On

᭤ ASK YOURSELF

Try drawing a realistic depiction of the scene from your window. Which monocular cues will
you use in your drawing?

᭤ TEST YOURSELF

What do we mean when we say that, in perception, “the whole is greater than the sum of its
parts”?

Answers to the Test Yourself questions can be found in Appendix E at the end of the book.

1/21/14 9:33 AM MyersAP_SE_2e_Mod19_B.indd 191 1/21/14 9:33 AM

Visual Organization and Interpretation Module 19 191

MyersPsyAP_TE_2e_U04.indd 191 2/20/14 8:11 AM

192 U n i t I V Sensation and Perception

Module 19 Review

19-1 How did the Gestalt psychologists 19-3 How do perceptual constancies help us
understand perceptual organization, organize our sensations into meaningful
and how do figure-ground and grouping perceptions?
principles contribute to our perceptions?

• Gestalt psychologists searched for rules by which the • Perceptual constancy enables us to perceive objects as stable

brain organizes fragments of sensory data into gestalts despite the changing image they cast on our retinas.
(from the German word for “whole”), or meaningful • Color constancy is our ability to perceive consistent color
forms. In pointing out that the whole may exceed the sum
of its parts, they noted that we filter sensory information in objects, even though the lighting and wavelengths
and construct our perceptions. shift.
• Brightness (or lightness) constancy is our ability to
• To recognize an object, we must first perceive it (see it as perceive an object as having a constant lightness even
when its illumination—the light cast upon it—changes.
a figure) as distinct from its surroundings (the ground). • Our brain constructs our experience of an object’s
We bring order and form to stimuli by organizing them color or brightness through comparisons with other
into meaningful groups, following such rules as proximity, surrounding objects.
continuity, and closure. • Shape constancy is our ability to perceive familiar
objects (such as an opening door) as unchanging in
19-2 How do we use binocular and monocular shape.
cues to perceive the world in three • Size constancy is perceiving objects as unchanging in
dimensions and perceive motion? size despite their changing retinal images.

• Depth perception is our ability to see objects in three • Knowing an object’s size gives us clues to its distance;

dimensions and judge distance. The visual cliff and other knowing its distance gives clues about its size, but we
research demonstrate that many species perceive the sometimes misread monocular distance cues and reach
world in three dimensions at, or very soon after, birth. the wrong conclusions, as in the Moon illusion.

• Binocular cues, such as retinal disparity, are depth cues that 19-4 What does research on restored vision,
sensory restriction, and perceptual
rely on information from both eyes. adaptation reveal about the effects of
experience on perception?
• Monocular cues (such as relative size, interposition, relative
• Experience guides our perceptual interpretations. People
height, relative motion, linear perspective, and light and
shadow) let us judge depth using information transmitted blind from birth who gained sight after surgery lack
by only one eye. the experience to visually recognize shapes, forms, and
complete faces.
• As objects move, we assume that shrinking objects are
• Sensory restriction research indicates that there is a
retreating and enlarging objects are approaching.
critical period for some aspects of sensory and perceptual
• A quick succession of images on the retina can create an development. Without early stimulation, the brain’s neural
organization does not develop normally.
illusion of movement, as in stroboscopic movement or the
phi phenomenon. • People given glasses that shift the world slightly to the

left or right, or even upside down, experience perceptual
adaptation. They are initially disoriented, but they manage
to adapt to their new context.

MyersAP_SE_2e_Mod19_B.indd 192 1/21/14 9:33 AM MyersAP_SE_2e

192 Unit IV Sensation and Perception 2/20/14 8:11 AM

MyersPsyAP_TE_2e_U04.indd 192

Visual Organization and Interpretation Module 19 193

Multiple-Choice Questions 3. Bryanna and Charles are in a dancing competition. It is Answers to Multiple-Choice
easy for spectators to see them against the dance floor Questions
1. A teacher used distortion goggles, which shifted the because of
wearer’s gaze 20 degrees, to demonstrate an altered a. the visual cliff. 1. a 3. e 5. a
perception. A student wearing the goggles initially b. the phi phenomenon. 2. a 4. a
bumped into numerous desks and chairs while walking c. color constancy.
around, but chose to wear the goggles for a half hour. d. sensory restriction. Answer to Practice FRQ 2
After 30 minutes, the student was able to smoothly avoid e. figure-ground relationships.
obstacles, illustrating the concept of 1 point: A gestalt is a unified whole.
a. perceptual adaptation. 4. The view from Narmeen’s left eye is slightly different We perceive the world in unified
b. visual interpretation. from the view from her right eye. This is due to which groups or patterns.
c. sensory restriction. depth cue? 1 point: Student must apply 2 gestalt
d. perceptual constancy. a. Retinal disparity principles to the perception of food on
e. binocular cues. b. Relative size a plate. Examples might include:
c. Linear perspective ᭹ Figure–ground: The food is the
2. What do we call the illusion of movement that results d. Relative motion
from two or more stationary, adjacent lights blinking on e. Convergence figure that stands out against the
and off in quick succession? ground of the plate.
a. Phi phenomenon 5. Bringing order and form to stimuli, which illustrates how ᭹ Similarity: A dozen Tater Tots would
b. Perceptual constancy the whole differs from the sum of its parts, is called be perceived as a group because
c. Binocular cues a. grouping. the tots all look pretty much alike.
d. Retinal disparity b. monocular cue. ᭹ Proximity: Green peas would be
e. Depth perception c. binocular cue. perceived as a group because they
d. disparity. would be near one another on
Practice FRQs e. motion. the plate.

1. Look at the relative size cartoon in Figure 19.5. Describe 2. Explain the meaning of the word gestalt as it applies to
how the artist who drew this cartoon incorporated perception. Then, apply any two gestalt principles to the
relative size, linear perspective, and interposition to perception of food on a plate.
create depth.
(3 points)
Answer

Specific explanations may utilize different aspects of the cartoon.
1 point: Relative size: We know the woman is closer to us
than the police officer, because she is drawn larger.

1 point: Linear perspective: We can tell that the sidewalk
is receding into the distance, because its sides pinch closer
together in the distance.

1 point: Interposition: We know the woman is closer to
us than the police officer, because our view of her partially
blocks our view of him.

1/21/14 9:33 AM MyersAP_SE_2e_Mod19_B.indd 193 1/21/14 9:33 AM

Visual Organization and Interpretation Module 19 193

MyersPsyAP_TE_2e_U04.indd 193 2/20/14 8:11 AM

TEACH 194 U n i t I V Sensation and Perception Leland Bobbé/CORBIS
TRM Discussion Starter
Module 20
Use the Module 20 Fact or Falsehood
student activity from the TRM to intro- Hearing
duce the concepts from this module.
Module Learning Objectives
ENGAGE
20-1 Describe the characteristics of air pressure waves, and
Active Learning explain the process by which the ear transforms sound
energy into neural messages.
Have band students bring in their
instruments to demonstrate how 20-2 Discuss the theories that help us understand pitch perception.
vibrations work with the different 20-3 Describe how we locate sounds.
instruments.
᭹ What produces the vibrations in

each instrument?
᭹ How does the instrument produce

louder and softer sounds?

20-1 What are the characteristics of air pressure waves that we hear as
sound, and how does the ear transform sound energy into neural

messages?

audition the sense or act of Like our other senses, our audition, or hearing, is highly adaptive. We hear a wide range
hearing. of sounds, but the ones we hear best are those sounds with frequencies in a range cor-
responding to that of the human voice. Those with normal hearing are acutely sensitive to
AP® Exam Tip faint sounds, an obvious boon for our ancestors’ survival when hunting or being hunted,
or for detecting a child’s whimper. (If our ears were much more sensitive, we would hear a
Pay attention to how many constant hiss from the movement of air molecules.)
pages are devoted to each
of the senses. Not only does We are also remarkably attuned to variations in sounds. We easily detect differences
this represent the complexity among thousands of possible human voices: Walking between classes, we immediately
of the sensory system, it also recognize the voice of a friend behind us. A fraction of a second after a spoken word
represents how likely you are stimulates the ear’s receptors, millions of neurons have simultaneously coordinated in
to find questions about that extracting the essential features, comparing them with past experience, and identifying
system on the AP® exam. More the stimulus (Freeman, 1991).
pages are devoted to vision than
hearing, and vision questions are But not everyone has this ability. Some years ago, on a visit to my childhood home, I
somewhat more likely to appear communicated with my then 80-year-old mother by writing on her erasable “magic pad.”
on the exam. Four years earlier she had transitioned from hearing loss to complete deafness by giving up
her now useless hearing aids.

“Do you hear anything?” I wrote.
“No,” she answered, her voice still strong although she could not hear it. “Last night
your Dad came in and found the TV blasting. Someone had left the volume way up; I
didn’t hear a thing.” (Indeed, my father later explained, he recently tested her by sneak-
ing up while she was reading and giving a loud clap just behind her ear. Her eye never
wavered from the page.)
What is it like, I wondered. “A silent world?”
“Yes,” she replied. “It’s a silent world.”

MyersAP_SE_2e_Mod20_B.indd 194 1/21/14 9:33 AM MyersAP_SE_2e

194 Unit IV Sensation and Perception 2/20/14 8:11 AM

MyersPsyAP_TE_2e_U04.indd 194

Hearing Module 20 195

And for her, with human connections made difficult, it became a socially isolated world. The sounds of music A violin’s Dennis MacDonald/Photo Edit
“Not having understood what was said in a group,” she reminisced, “I would chime in and short, fast waves create a high pitch,
say the same thing someone else had just said—and everyone would laugh. I would be so a cello’s longer, slower waves a lower ENGAGE
embarrassed, I wanted to fall through the floor.” Increasingly, her way of coping was to pitch. Differences in the waves’ height,
avoid getting out onto the floor in the first place. She shied away from public events and or amplitude, also create differing Applying Science
found excuses to avoid people who didn’t understand. degrees of loudness. (To review the
physical properties of light and sound Have students measure the decibels of
Our exchange left me wondering: Will I—having inherited her progressive hearing waves, see Figure 18.2 in Module 18.) different sounds common to school:
loss—also become socially isolated? Or, aided by today’s better technology, can I keep my the bells that signal class changes, hall
private vow not to repeat her past? Hearing allows mind-to-mind communication and en- AP® Exam Tip noise, and different teachers’ voices. Do
ables connection.Yet many of us can and do connect despite hearing loss—with help from these sounds fall within the safe range
technology, lip-reading, and signing. For me, it’s worth the effort. Communicating with oth- Note that both light and sound of decibels?
ers affirms our humanity as social creatures. travel in waves. In each case,
the amplitude and length of the ENGAGE
So, how does hearing normally work? How do we harvest meaning from the air pres- waves are important.
sure waves sent from another’s mouth? Active Learning
frequency the number of
The Stimulus Input: Sound Waves complete wavelengths that pass a Students can also demonstrate bone-
point in a given time (for example, conducted sound with a metal coat
Draw a bow across a violin, and you will unleash the energy of sound per second). hanger tied to the center of a thin
waves. Jostling molecules of air, each bumping into the next, create pitch a tone’s experienced highness string about 4’ long. They should first
waves of compressed and expanded air, like the ripples on a pond or lowness; depends on frequency. press each end of the string into each
circling out from a tossed stone. As we swim in our ocean of mov- middle ear the chamber between ear with the tips of the index fingers
ing air molecules, our ears detect these brief air pressure changes. the eardrum and cochlea containing while plugging their ears. Then they
(Exposed to a loud, low bass sound—perhaps from a bass guitar or three tiny bones (hammer, anvil, should ask someone to tap the coat
a cello—we can also feel the vibration. We hear by both air and bone and stirrup) that concentrate the hanger with a knife or fork. John Fisher
conduction.) vibrations of the eardrum on the reports that the effect will sound like
cochlea’s oval window. the city of London’s famous clock
Like light waves, sound waves vary in shape. The amplitude of cochlea [KOHK-lee-uh] a coiled, Big Ben.
sound waves determines their loudness. Their length, or frequency, bony, fluid-filled tube in the inner
determines the pitch we experience. Long waves have low frequency—and low pitch. Short ear; sound waves traveling through
waves have high frequency—and high pitch. Sound waves produced by a violin are much the cochlear fluid trigger nerve
shorter and faster than those produced by a cello or a bass guitar. impulses.
inner ear the innermost part of
We measure sounds in decibels, with zero decibels representing the absolute threshold the ear, containing the cochlea,
for hearing. Every 10 decibels correspond to a tenfold increase in sound intensity. Thus, nor- semicircular canals, and vestibular
mal conversation (60 decibels) is 10,000 times more intense than a 20-decibel whisper. And sacs.
a temporarily tolerable 100-decibel passing subway train is 10 billion times more intense
than the faintest detectable sound.

The Ear

The intricate process that transforms vibrating air into nerve impulses, which our brain
decodes as sounds, begins when sound waves enter the outer ear. A mechanical chain
reaction begins as the visible outer ear channels the waves through the auditory canal to
the eardrum, a tight membrane, causing it to vibrate (FIGURE 20.1 on the next page). In
the middle ear three tiny bones (the hammer, anvil, and stirrup) pick up the vibrations
and transmit them to the cochlea, a snail-shaped tube in the inner ear. The incoming
vibrations cause the cochlea’s membrane (the oval window) to vibrate, jostling the fluid
that fills the tube. This motion causes ripples in the basilar membrane, bending the hair
cells lining its surface, not unlike the wind bending a wheat field. Hair cell movement
triggers impulses in the adjacent nerve cells. Axons of those cells converge to form the
auditory nerve, which sends neural messages (via the thalamus) to the auditory cortex in
the brain’s temporal lobe. From vibrating air to fluid waves to electrical impulses to the
brain: Voila! We hear.

1/21/14 9:33 AM E N G AG EMyersAP_SE_2e_Mod20_B.indd 195 1/21/14 9:33 AM

Enrichment

The technical name for the collection of bones
in the middle ear is ossicles. Each bone also has
a technical name:
᭹ hammer—malleus
᭹ anvil—incus
᭹ stirrups—stapes

Hearing Module 20 195

MyersPsyAP_TE_2e_U04.indd 195 2/20/14 8:11 AM

196 U n i t I V Sensation and Perception

ENGAGE (a) OUTER EAR MIDDLE EAR INNER EAR

Enrichment Semicircular canals

Why does our own voice sound unfa- Bones of the
miliar when we hear it on tape? When
we listen to ourselves speak, we hear middle ear Bone
both the sound conducted by airwaves
to the outer ear and that sound car- Auditory nerve
ried directly to the auditory nerve by
bone conduction. The latter is easily Sound Cochlea
demonstrated by clicking the teeth or waves
munching popcorn, or by striking the
prongs of a fork on a table and quickly Eardrum
applying its handle to the bone behind
the ear. An even more resounding Auditory Oval window
effect will be produced if the fork’s canal (where stirrup attaches)
handle is clenched between the teeth.
The strictly air-conducted sound that Hammer Anvil Cochlea, Auditory cortex
others normally hear (like a sound partially uncoiled of temporal lobe
we hear when our voice is on tape) is
thinner. Students can hear the sound (b) Sound Auditory nerve
waves conducted by bone if they plug waves Nerve fibers to auditory nerve
their ears and talk in a normal voice. Enlargement of middle ear
and inner ear, showing
Fisher, J. (1979). Body magic. New York: Stein cochlea partially uncoiled
and Day. for clarity

Figure 20.1 Eardrum Stirrup Oval window Protruding hair cells
Basilar membrane
Hear here: How we transform Motion of fluid in the cochlea
sound waves into nerve
impulses that our brain My vote for the most intriguing part of the hearing process is the hair cells—“quivering
interprets (a) The outer ear funnels bundles that let us hear” thanks to their “extreme sensitivity and extreme speed” (Goldberg,
sound waves to the eardrum. The 2007). A cochlea has 16,000 of them, which sounds like a lot until we compare that with an
bones of the middle ear (hammer, eye’s 130 million or so photoreceptors. But consider their responsiveness. Deflect the tiny
anvil, and stirrup) amplify and relay bundles of cilia on the tip of a hair cell by the width of an atom—the equivalent of displacing
the eardrum’s vibrations through the top of the Eiffel Tower by half an inch—and the alert hair cell, thanks to a special protein
the oval window into the fluid-filled at its tip, triggers a neural response (Corey et al., 2004).
cochlea. (b) As shown in this detail of
the middle and inner ear, the resulting Susumu Nishinaga/Science Source
pressure changes in the cochlear
fluid cause the basilar membrane to
ripple, bending the hair cells on its
surface. Hair cell movements trigger
impulses at the base of the nerve
cells, whose fibers converge to form
the auditory nerve. That nerve sends
neural messages to the thalamus and
on to the auditory cortex.

Be kind to your inner ear’s hair 1/21/14 9:33 AM MyersAP_SE_2e
cells When vibrating in response to
sound, the hair cells shown here lining
the cochlea produce an electrical signal.

MyersAP_SE_2e_Mod20_B.indd 196

196 Unit IV Sensation and Perception 2/20/14 8:11 AM

MyersPsyAP_TE_2e_U04.indd 196


Click to View FlipBook Version