How the brain works

100 101BRAIN FUNCTIONS AND THE SENSES
Unconscious Movement

Reflex actions Additional relay KEY
neurons send
Reflexes are split-second responses signal to brain Motor neuron Signals to spinal cord
to danger that we do not have to learn sends signal Signals to muscle
or even think about; the body reacts 4 to muscle Signals to brain
automatically. Reflex actions involve the to contract
same muscles that are used in voluntary 5
movements, but the initial, instantaneous 3 SPINAL Receptors in 1
response does not involve the brain. CORD skin detect heat
Instead, the signal from the sensory MUSCLE from flame
nerves travels to the spinal cord, which
triggers a response that travels along the 2
motor nerves. Additional signals are sent
to the brain afterward, to encode the Relay neurons Sensory neurons STIMULUS
memory in case the danger recurs. in spinal cord send signal to
generate response spinal cord

OUR NEURONS AND Bypassing the brain
NERVE PATHWAYS CHANGE Reflexes involve a simple neural
CONSTANTLY IN RESPONSE response called the reflex arc.
TO EXPERIENCES Receptors in the skin and muscles
send a danger signal along sensory
neurons to the spinal cord; there, relay
neurons synapse with motor neurons
to trigger a fast response.

Movement Ball coming DEVELOPING COMPETENCE
sequence toward player
begins Anyone learning a new skill passes
through several stages. Beginners have
Primary motor area plans to work hard to acquire competence.
and executes movement With practice, neural pathways
develop until the learner can perform
Premotor well without thinking about it.
area plans
movement Unconscious
competence
MOTOR Performing skill
CORTEX is automatic

VISUAL Conscious
CORTEX competence
Able to use skill,
3 Planning 4 Conscious action but only with effort
The brain combines real-time By the time the player becomes
visual information and stored programs conscious of acting, the movement Conscious
for movement sequences to create a sequence is well underway. The action incompetence
plan of action. This is first rehearsed in is most likely to be effective if the Aware of skill needed
the premotor area and then sent to the person has sufficient skill, stored but lacking proficiency

Unconscious
incompetence
Unaware of skill needed
and lack of proficiency

primary motor cortex. knowledge, and information.

Mirror Mirroring movement
Neurons
Some scientists suggest that mirror neurons may play
Learning does not just involve a role in learning how to imitate movement. In this
practicing a new skill—we also theory, information on the purpose of an action is
learn by watching others. This passed to mirror neurons from brain areas such as the
kind of learning is thought to prefrontal cortex, which is responsible for analysis.
involve nerve cells in the brain Mirror neurons in various motor areas then encode a
called mirror neurons that allow simulation of that action, which becomes part of our
us to experience actions without own motor programming. We can then go on to use this
actually performing them. “program” if we need to carry out the action ourselves.

What are mirror neurons? Observing an action
Mirror neurons respond differently to various actions of the
Mirror neurons are brain cells that fire both when face and limbs. In particular, neurons in different brain areas
we perform an action and when we see someone are activated for movements of the body itself, such as chewing,
else performing that action. They were first and those focused on a visible object, such as biting a fruit.
discovered in monkeys but have since been found
in humans, too. Most studies have used functional Various motor areas
magnetic resonance imaging (fMRI; see p.43), activated, including
but one study involved people who had electrodes those linked to
implanted into their brains. In this instance, mirror controlling mouth
neuron cells were detected in the supplementary and jaw movements
motor area, where movement sequences are
planned, as well as in the hippocampus, OBSERVER
which governs memory and navigation.
Part of parietal
Where are they? lobe activated by
Mirror neurons
have been found sight of action
in several cortical targeted at object
areas as well as in
structures deeper
within the brain,
such as the
hippocampus.

KEY Primary motor area Parts of premotor
Premotor area Somatosensory area area and Broca’s area
Part of Broca’s area Inferior parietal area (which plays a role in
understanding another
Inferior frontal gyrus person’s movement)
Supplementary motor area activated

OBSERVER

102 103BRAIN FUNCTIONS AND THE SENSES
Mirror Neurons

DO OTHER YAWNING
ANIMALS HAVE
MIRROR NEURONS? Mirror neurons may play a role
in “contagious yawning”—the
Mirror neurons were first impulse to yawn when we see
discovered in macaque someone else yawning. FMRI
monkeys. They have also scans of people who watched
been found in some birds, videos of someone else yawning
such as songbirds, and showed activity in the right
more recently in rats. inferior frontal gyrus, an area
associated with mirror neurons.

1 Watching a body movement Understanding intention
Watching a person perform an
action not linked to an object, such as Mirror neurons are activated in different ways
chewing, activates the premotor area when we see others performing particular actions,
in the observer. This is an area that is suggesting they could play a role in decoding
linked to rehearsing planned intention. Watching similar actions observed in
sequences of action. It also different contexts—such as watching someone
activates areas in the primary pick up a cup either to drink from it or to clean it
motor area associated with up—triggers different levels of neural activity in
the inferior frontal gyrus; an area of the brain that
directs our attention to objects in our environment.

mouth and jaw movements.

0.7 Strong
response from
0.6

0.5 mirror neurons

ACTION WITH 0.4
NO OBJECT Neural activity
0.3 DRINKING

CLEANING0.2

0.1

0 Weak response
from mirror
2 Watching action –0.1 neurons
on an object –0.2

Watching an action directed –0.3 Time

at an object, such as a person Intention and brain activity
biting into a fruit, activates Activity in the brain is greater when a person watches someone
similar areas of the motor cortex. lift a cup to drink rather than when they watch someone pick it
However, mirror neurons also up to clear it away. Some scientists suggest this may be because
fire in an additional area, the drinking has a greater biological function than cleaning.
parietal cortex, which is involved
in interpreting sensory
input as well as providing
information about the THE BRAIN WAVES OF
body’s position. MUSICIANS COME INTO
SYNC WHEN THEY
ACTION WITH PLAY TOGETHER
AN OBJECT



COMMUNICATION

Emotions

Emotions are physiological responses to HORMONES THAT TRIGGER
external events, shaped by experience, EMOTIONAL RESPONSES ARE
that are accompanied by distinctive ABSORBED IN 6 SECONDS
feelings. They evolved to push us away
from danger and toward reward. eptance Awe
S
Acc
Basic emotions erenity D miration
nfusion S Ad
Research suggests that there are four Joy isfaction Relief
physiologically distinct conscious feelings:
anger, fear, happiness, and sadness. Co isgust
Aspects of these combine and allow A
us to feel a range of emotions. Broadly, icipation
emotions are positive or negative Sat
experiences, which vary in intensity. Ant
Different emotional states are associated nxiety
with particular physiological changes
that affect how a person behaves and urprise
thinks. For example, we view the world
differently when we are relaxed and GER FEA
when we are afraid. This coordination AN R
of physiology, behavior, and thought SADNE
with feeling is what makes us adapt
our behavior in response to events.

Emotions
Other emotional experiences stem from the four
key ones. A recent study found there may be 27
types of emotional experiences, some of which are
shown here. Certain emotions lie along gradients,
such as moving from anxiety to fear to horror.

WHY DO WE CRY? APPINESS

Only humans cry, and nobody is certain
why we do it—especially given that both
sadness and joy can evoke tears. Crying
serves an interpersonal function,
signaling that we are in emotional
distress to evoke appropriate
social responses. It is also
cathartic, enabling full
emotional engagement
and processing that is
good for mental health.

SS H

106 107COMMUNICATION
Emotions

The anatomy of emotion SEROTONIN Brain produces Low levels
majority of of serotonin
In response to a stimulus, the brain initiates hormonal hormones in brain
changes that, in turn, trigger physiological changes relating to
that prime us to respond in appropriate ways to the happiness Mildly increased
current emotional state. Heart rate changes, altered bodily feelings
blood flow to the muscles, and sweating are associated Heart rate around neck
with heightened emotions. These changes can be felt decreases and chest
consciously, increasing the emotional intensity.
Large amount Low levels
WHAT IS THE PURPOSE Happiness and sadness of serotonin of serotonin
OF LAUGHTER? Serotonin, dopamine, produced by produced
oxytocin, and endorphins large intestine
The relaxation that results are hormones that affect Sensations
from a bout of laughter our happiness profoundly. Feeling of of decreased
Emotions are felt across well-being limb activity
inhibits the biological fight- the body, with different reported all
or-flight response. emotions felt in different over body SADNESS
places. The effects of
serotonin are shown here.

KEY
Positive feelings reported

Negative feelings reported

HAPPINESS

Unconscious emotions Sensory Hippocampus
cortex The hippocampus
For primitive automatic responses, such as the Sensory information processes consciously
fight-or-flight reflex, speed is critical. Emotionally transmitted to the perceived information to
charged stimuli presented too fast to be consciously sensory cortex is extensively form memories. It also
perceived can evoke emotional responses and processed toward conscious compares incoming signals
activate the amygdala. These initial responses perception and integrated to previous memories to
shape how the cortex processes information. The with stored information. adjust emotional
amygdala is involved in emotional memory that This takes time.
may be automatically activated in the future. responses.

SLOW AND ACCURATE ROUTE

Thalamus QUICK Amygdala Hypothalamus Two routes
Incoming AND DIRTY The amygdala Signals from the Conscious processing
information is relayed instantly assesses the amygdala trigger of emotions involves
to the amygdala for quick ROUTE emotional importance of hormonal changes and integrating sensory
assessment and action and incoming information output to the autonomic information with stored
also to cortical areas where content and rapidly sends nervous system to prime the memories and reasoned
it enters conscious signals to other areas for body to respond to evaluations of a situation—
awareness. immediate bodily action. emotional stimuli. this is the “slow and
accurate route.” In contrast,
unconscious responses, via
the “quick and dirty route,”
happen much faster. The
prefrontal cortex is
important in conscious
emotional regulation.

Fear and Anger Hypothalamus
Thalamus
Fear and anger trigger the release of hormones in the body
that prepare us to deal with threats. In the modern world, Amygdala
however, long-term anxiety can cause overactivation of the Visual cortex
sympathetic nervous system and lead to health problems.
Responding to danger
Fight or flight Saliva production Signals travel to the thalamus and amygdala,
reduces which triggers the hypothalamus to produce
When we see a possible threat, visual Saliva secretion fight-or-flight hormones. A slower, conscious
information travels to our amygdala, slows down when pathway involving the cortex also assesses the
a tiny part of the brain that processes we are afraid. This situation (see p.107).
emotion. The amygdala sends a signal causes a dry mouth.
to the hypothalamus, which activates Pupils dilate
the sympathetic nervous system, Our pupils enlarge,
preparing the body to react to danger letting in more light
(see p.13). The hypothalamus also sends so we can see the
signals to the pituitary and adrenal threat more clearly.
glands, which secrete hormones such
as cortisol and adrenaline. The combined
effect of these pathways is to initiate our
fight-or-flight reflex, which prepares our
bodies to attack or run away.

Muscles tense Digestion slows Breathing rate rises Heart rate Sweating increases Blood vessels
The muscles in our To avoid wasting This oxygenates our increases Our sweat glands constrict
arms, legs, and energy, digestive muscles, preparing Our heart beats faster are triggered, and Blood flow is
shoulders prepare activity falls. In them for action. But to pump oxygen- we begin to sweat, directed away from
themselves for action. extreme cases, we it can also cause and-nutrient-rich ensuring we remain the surface of the
We may feel tense may vomit to eject symptoms of blood to where it is cool if physical skin, so we may
or “wound up.” undigested food. hyperventilation. needed in the body. exertion is needed. appear pale.

Immune system Blood sugar spikes Blood flows Bladder 4 PERCENT
activity reduced Sugar stores are to muscles muscles relax
In the moment, released from the Blood carries This causes us to OF PEOPLE
dealing with liver to provide the nutrients and need to urinate, WORLDWIDE HAVE
infections is not muscles with the oxygen to the which rids the ARACHNOPHOBIA,
crucial, so the energy they need to muscles, readying body of excess A FEAR OF SPIDERS
immune system shuts work. Fat stores are them to fight or weight and makes
down to save energy. also mobilized. flee from danger. us faster and lighter.

Angry or afraid? Panic attacks

The bodily reactions to fear and anger are similar. Panic attacks are physical reactions to fear or anxiety. Symptoms include
It is mainly the way we interpret the sensations we a pounding heart; chest pain; rapid, shallow breathing; and sweating.
experience that determines whether we feel afraid Initially, sufferers can think they are having a heart attack. The first step to
or angry. One theory suggests that if we know why a break the cycle is to recognize that you are experiencing a panic attack.
negative event happened, and who was responsible for
it, we will feel angry. If we are unable to figure out Panic attack The trigger COMMUNICATION
the cause, or it is out of our control, we will feel fear. Left unchecked, this can Panic attacks can have a single
spiral into a full-blown Fear and 108 109Anger
Context is key trigger, like a phobia, or
Whether we react with fear or panic attack. Sufferers 6
anger to a particular stimulus is 1 begin without warning,
often conditioned by its context. may even fear they
are dying. as stress and anxiety
build up.

YOU LIVE ALONE Symptoms Interpreting
danger
increase Your brain
You live alone Without being More hormones
so know there able to figure are released, construes the
Fight-or- should not be out the cause, and symptoms feelings as
flight reflex anyone here. you feel afraid. get worse, 5 The panic 2 danger and
is triggered cycle
releases fight-or-
increasing flight hormones.
anxiety further.
You are woken
by loud noises LIVE WITH ROOMMATE Anxiety builds Physical effect
downstairs in Unaware of the Physical sensations,
the middle of triggers and unsure such as an increase in
why this is happening, 4 3 heart rate, occur in
the night.

You recall your Sensations are your anxiety increases. response to the hormones.
roommate interpreted as
was out and anger about
inconsiderate
realize she has
come back. behavior.

REFLEX FACIAL EXPRESSIONS Feelings CMOROTTEOXR CONSCIOUS FA CIAL EXPRESSIONS
Ongoing feelings are
EMOTIONAL shaped by the senses, MCOORTOTERX
CENTER disposition, memories,
OF BRAIN
body signals, and
attention.

Signals Conscious
Bodily signals such intervention
as heart rate, sweating, Analysis of situations
muscle tension or by the frontal cortex
shapes expectations
relaxation, and and adjusts emotional
trembling all help
processing.
shape feelings.

REFLEX SMILE Expressions CONSCIOUS SMILE
Reflex facial expressions Facial expressions Conscious facial expressions
Emotions generate facial expressions are both products After we have started to experience
without our control. For example, and influencers of an emotion, we can change our
when we hear good news, we emotion—smiling, for
automatically smile. The amygdala and example, elevates facial expressions to hide or
other parts of the limbic system initiate reinforce our true emotions. Such
mood.
these reflex actions. action involves conscious
Motor Motor engagement of the motor cortex.
neuron neuron

Conscious How emotions form
Emotion Both reflex and conscious expressions are mediated
by the motor cortex, but reflex ones are signaled to
Emotions are felt consciously, and the motor area directly from the limbic system rather
whether they are positive or negative, than via the frontal lobes. We can also consciously
changeable or constant, they have modify our physical responses to emotions.
major effects on our quality of life.
Conscious feelings ceaselessly interact Forming emotions
with the unconscious processes that
also shape our emotions. Emotional responses are complex and dynamic. They
arise when rapid innate responses to stimuli interact
with detailed analysis. Innate responses evolved as the
most beneficial reactions to key stimuli. Once such
stimuli have caught a person’s attention, reasoned
assessment follows. Then, how a person’s emotions
change is shaped by their disposition, past experience,
and how they assess multiple streams of information.

110 111COMMUNICATION
Conscious Emotion

Emotional reactions KEY SEROTONIN
Amygdala
Emotional responses evolve over time, Primary visual cortex Alongside dopamine and
from initial protective responses to more Frontal cortex noradrenaline, serotonin is
considered responses. Imagine a friend Fusiform gyrus (face a neurotransmitter that plays
leaping out on you: first, you feel shock recognition area) a key role in regulating mood.
or fear, but as the brain processes what is Motor cortex Although it is not as simple as
happening, you transition to calm. The high serotonin equals happiness
first stage involves attention being grabbed Parietal cortex and low equals sad, decreases in
and the amygdala responding early to this molecule are associated with
prime the conscious brain to “expect” Signal travels depression and anxiety.
an important perception. to motor and Many antidepressant
parietal cortex medications act
Less than 100 milliseconds by increasing
Sensory information goes to Signal travels brain levels
the amygdala, which sends to amygdala of serotonin.
signals to the parietal cortex and then Exercise can
to the motor cortex to produce fast Signal from help, too—for
reactions to emotional stimulus, such sensory areas example, taking
as when fleeing from danger. a brisk walk
Recognition or dancing can
100–200 milliseconds pathway raise serotonin levels.
The information then arrives
in the frontal lobes, where it Signal from EMOTIONS ARE
becomes conscious and appropriate frontal lobe to CONTAGIOUS—
action is planned. motor cortex HUMANS MIMIC
EACH OTHER’S
Information EXPRESSIONS
registers in
frontal cortex

350 milliseconds
Considered reactions are
then conveyed back to
the motor cortex, which signals
appropriate bodily responses.

Emotions versus moods ADAPTIVE BEHAVIORS

Emotions are usually transient— EMOTION POSSIBLE STIMULUS ADAPTIVE BEHAVIOR
arising from thoughts, activities, or Anger
events that act as cues for adaptive Fear Challenging behavior from “Fight” reaction prompts dominant and
behaviors. Moods last for hours, Sadness another person threatening stance or action
days, or even months. For example, Disgust
emotion might be experiencing a Surprise Threat from stronger or “Flight” to avoid threat; or act to socially
sudden rush of joy at seeing a dominant person appease the threatening person
friend waiting to greet you
compared to a lingering mood of Loss of loved one Backward-looking state of mind and
sadness or worry after losing a job. passivity, to avoid additional challenge
Emotions tend to be expressed in
the moment, while moods are not. Unwholesome object (e.g., rotting Aversion behavior—remove oneself from
food or unclean surroundings) the unhealthy environment

Novel or unexpected event Attention on object of surprise maximizes
sensory input that guides reaction

Reward Centers Rush of dopamine tells
brain to repeat activity
The brain’s reward system evolved because it helped Attention
us seek out things that are important for our survival. focused on Dopamine neurons
But if this system is hijacked, it can lead to addiction. activity activated and project
to other brain areas

Reward pathways FRONTAL CORTEX NUCLEUS
ACCUMBENS
When we do something that is important for our survival,
such as eating when hungry, or having sex, neurons that SUBSTANTIA
trigger the release of the neurotransmitter dopamine are VTA NIGRA
activated in the ventral tegmental area (VTA). These send
LIMBIC SYSTEM
signals to an area called the nucleus accumbens—a rush in Route to reward
The reward system starts in the VTA in the
dopamine here tells the brain this is a behavior that should midbrain, then passes to the nucleus
accumbens in the basal ganglia and then the
be repeated. Neurons also send signals to the frontal cortex, frontal cortex. Dopamine also travels from
which focuses attention on the beneficial activity. the substantia nigra to the basal ganglia.
This pathway affects motor control.
LIGHT ENTERS EYE

1 Stimulus Sensory
The initial stimulus can originate information
outside the body, such as the sight of registers in
food, or from within, such as falling limbic system
glucose levels.

2 Urge 3 Desire
Dopamine released from the The urge may be registered as
VTA to the nucleus accumbens drives us a conscious desire in the cortex, but
to seek out and work for the reward sometimes it goes undetected, or even
that is linked to the stimulus. opposes our conscious desires.

5 Reward 6 Learning
The reward triggers parts of the If the reward is better than
brain known as “hedonic hot spots” to expected, the brain releases more
release opioid-like neurotransmitters, dopamine, strengthening the connection
giving a sense of pleasure. between stimulus and reward.

4 Action
A region of the frontal cortex
weighs the inputs and decides whether
to seek the reward. The body then
acts to reach it.

112 113COMMUNICATION
Reward Centers

Addiction UP TO 60%
OF ADDICTION
Most drugs of abuse cause huge amounts of dopamine to build up RISK STEMS
in the reward system—far more than natural rewards like food or FROM GENETIC
sex. This creates a powerful drive to seek out more of the drug. It FACTORS
also causes the brain to reduce the number of dopamine receptors,
so natural rewards no longer give the same sensation. This means
the user loses the urge to seek out things like food and social
engagement. Instead, drug cues become powerful triggers for
dopamine release, causing intense cravings, even when the user
consciously wants to stop and no longer enjoys the drug.

ESPONSE Vesicles in nerve NCE Normal
cell release dopamine
PRNESEYUNRAOPNTIC neurotransmitters PRNESEYUNRAOPNTIC release
Dopamine Dopamine
NORMAL R
TOLERA

SYNAPSE SYNAPSE

RECEPTORS Many receptors RECEPTORS Not many receptors

POSNTESUYRNOANPTIC POSNTESUYRNOANPTIC

Flooded with dopamine Under tolerance
Some drugs of abuse increase dopamine release, while Over time, the brain reduces the number of dopamine
others stop it from being recycled. The buildup in the synapse receptors to counteract the excess. Now, when normal
produces a large response in the brain, triggering the drive amounts of dopamine are released, they have little effect.
to seek out more of the drug. Environmental cues become The user may need bigger and bigger doses of the drug to
linked with the drug and can trigger cravings in the future. feel its effect, and their desire for other rewards decreases.

WHY IS JUNK WANTING VERSUS LIKING
FOOD SO TASTY?
The reward pathway is often called
Most junk food contains a “pleasure pathway,” and dopamine
lots of sugar, salt, and fat, a “pleasure chemical,” but this is not
which trigger our reward accurate. Dopamine in the nucleus
system. This would have accumbens drives “wanting” of a
helped us survive when reward, but it is common for addicts
to experience strong cravings without
food was scarce. liking the effects of the drug. Pleasure
is likely to be caused by other
neurotransmitters such as opioids
or endocannabinoids.

Sex and Love

Sexual reproduction is fundamental DOPAMINE
to passing on our genes. Multiple
emotions evolved that accompany and Reward Brain
facilitate this process, which together pathway in produces
can create the feeling of love. brain triggered dopamine

Love and attraction SEROTONIN Feelings of
excitement
The scientific study of love and sexual and euphoria
behavior has identified three primary
components: attraction, attachment, and lust. Serotonin Brain
These states all occur on different timescales levels produces
and involve different regions of the brain less serotonin
producing an array of chemical messengers— reduced
neurotransmitters and hormones. Lust and
attraction are closely interlinked, and both are Loss of NORADRENALINE
transient, passing in a relatively short time. appetite,
For relationships to last, these states must insomnia,
yield profound attachment, which involves feelings of
long-term changes to the brain. obsession

KEY
Prefrontal cortex

Hypothalmus

Pituitary gland

Brain areas Noradrenaline Brain produces
The hypothalamus and pituitary gland control early levels increased noradrenaline
hormone-led phases of bonding. The prefrontal cortex then
mediates the emotional control involved in attachment. Attraction Energy levels
Surges of the chemical messengers dopamine increased,
THE LOVE DRUG and noradrenaline combine with reduced levels heart races,
of serotonin to produce urgent feelings of appetite
Oxytocin, which is released by the hypothalamus, attraction. In an energized state—with racing decreased,
has long been known as the hormone that heart, sweaty palms, and little appetite—we think insomnia
induces labor in mammals. constantly about our lover, craving their company.
It was then found to be
crucial for mother-offspring
bonding and later to
be central to forming
long-term attachments
in sexual and social
relationships.

114 115

OXYTOCIN REDUCES Facial symmetry
ACTIVITY IN THE
BRAIN’S FEAR CENTER A person’s face is key to how
attractive others find them.
OXYTOCIN Humans and monkeys prefer
symmetrical faces—symmetry
Brain is an indicator of good health
produces and genetics. Many species also
oxytocin favor sexually dimorphic faces,
males preferring feminine faces
Feelings of and vice versa. These factors
bonding and interact: higher facial symmetry
contentment increases a face’s perceived
femininity or masculinity.

Oxytocin SEX HORMONES KEY
levels
Symmetrical Asymmetrical
increased face face

Vasopressin Hypothalamus FEMALE MALE
levels triggers 69% Percentage of

increased production of Increased levels people who
sex hormones of testosterone
and estrogen found face 85%
by testes or
ovaries Increased sex-typical
libido
Brain
produces 31% 15%
vasopressin European
When shown composite faces with high
Feelings of or low symmetry, European observers
bonding and judged high-symmetry faces to appear
attentiveness more feminine or masculine.

62% 60%

VASOPRESSIN

37% Percentage of 39%
people who
Attachment Lust found face
The hormones oxytocin and vasopressin Lust is the primeval urge to engage in sex-typical
have multiple effects—including making sexual relationships, driven by the sex
us feel more protective of our object of hormones testosterone and estrogen. Hadza
attraction and attentive to their needs. While they increase libido in men and Similar results were found in the Hadza
They stimulate long-term bond formation women respectively, they alone do people, an indigenous Tanzanian ethnic
but can increase distrust of others. not induce lasting connections. group. This suggests that the link between
symmetry and attractiveness is universal.

Early stages of

forming an angry or

disgusted expression

GER are similar GUST NESS

AN
DIS
SAD

Brows lowered Nose Raised
wrinkled inner brows

Lips pressed together Upper lip raised Lowered
mouth

Anger causes the brows to lower, the Disgust is associated with a wrinkled A sad person turns down the corners of
lips to be pressed together, and the eyes nose with the cheeks and upper lip their lips while raising their inner brows
being raised. The wrinkled nose stops
to bulge. An observer would be wary the person from inhaling offensive odors. and lowering the outer brow. This
of the person signaling anger. expression might evoke sympathy.

Universal expressions MICRO EXPRESSIONS

Psychologists have found that there are six universal emotions: anger, Micro expressions are tiny,
disgust, sadness, happiness, fear, and surprise. Like primary colors, involuntary, and often barely
they combine to give rise to the many emotions we experience. Each perceptible facial expressions.
one is linked to a distinctive facial expression that is similar in every They last half a second or less,
culture. Expressions are part biologically and part socially driven. When and the person making them
surprised or fearful, for example, widening the eyes takes in more may be unaware that this form
light to better survey the situation. But other aspects of expressions of “emotional leakage” is
evolved to convey social signals to members of the same species. revealing their true feelings.

Expressions

Expressions are extensions of emotions. They allow
us to communicate our feelings to others and to
infer the thoughts and feelings of people around us.
Psychologists believe there are six basic emotions,
each with an associated expression.

PINESS 116 117COMMUNICATION
Expressions
Raised cheeks AR PRISE

Raised brows
HAP
FE

SUR

Eye widening and Jaw dropped
other features are
common to early
stages of expressing

fear or surprise

When we are happy, we raise the The distinctive fearful expression In surprise, people quickly open their
corners of our mouths and also raise includes raised eyebrows, wide eyes, eyes wide and arch their brows, while
our cheeks—the skin under the eyes and the mouth falling open. This signals
wrinkle, and the eyes are said to sparkle. their lower jaw drops, leaving the
others to be on high alert. mouth agape.

Motor cortex Motor cortex

Smiling Frontal cortex
Amygdala
A smile can either be a genuine
expression of positive mood or a Signal causes muscles
conscious, socially motivated action. around mouth to contract
Genuine smiles are unconscious
acts that involve different muscle and pull lips sideways in
groups to social smiles. While both both types of smiles
involve a stretched mouth with lips
upturned at the corners, the genuine Signal causes small muscles
smiling person constricts muscles around eye socket to contract
that raise the cheeks, producing
“crow’s feet” around the eyes. Genuine smile Conscious smile
Conscious smiles vary in their exact The muscular contractions involved in genuine Conscious control of social smiling involves
structure and are used in an array smiles are triggered by signals from the brain’s activation of the frontal cortex and signals
of social interactions—they can be emotional centers, such as the amygdala, from the motor cortex. The mouth muscles
socially bonding but also used to usually operating without our awareness. contract, but we can’t control the eye muscles.
signal dominance, and people may
also smile to mask embarrassment.

Body HAPPY
Language
From a resting
Body language is nonverbal point, pupils can
communication, in which our shrink or expand
thoughts, intentions, or feelings are
expressed by physical behaviors NORMAL Iris muscles
such as body posture, gestures, eye contract to
movements, and facial expressions. enlarge pupil

DILATED

Nonconscious communication Eye signals
Pupils frequently shift size and can
Social interactions between people involve signal various things. A dilated
complex streams of nonverbal communication pupil may indicate surprise orAGGRESSIVE
that are processed in parallel to speech. Many attraction. Constricted
aspects of body language arise instinctively— pupils are associated
eye movements, facial expressions, and with negative
posture, for example, all change without emotions such
conscious control. These movements can as anger.
therefore reveal unspoken intentions. Body MORE THAN 50 PERCENT
language is also used to signal social intentions OF COMMUNICATION
overtly, such as when blowing a kiss. The IS BASED ON OUR
richness of this communication involves the BODY LANGUAGE
whole body and our brains are attuned to it.

Superior temporal Orbitofrontal

gyrus cortex

Amygdala DO GESTURES
HAVE THE SAME
MEANING AROUND

THE WORLD?

No, many gestures are
culturally specific. A simple

hand gesture can have
different meanings for

different societies.

Brain processes
Processing body language involves areas like the amygdala,
which receives emotional content; part of the superior
temporal gyrus, which responds to seeing human
movement; and the orbitofrontal cortex, which analyzes
meaning. Special cells, called mirror neurons (see pp.102–
103), are also activated when you see someone else moving.

118 119COMMUNICATION
Body Language

SAD

Facial expressions Gestures
Facial expressions reveal much about
a person’s emotions (see pp.116–117). Most body language is performed unconsciously, but
The eyes and the mouth, in particular, we have more conscious control over our gestures, which
automatically respond to strong feelings, are movements of the body used to convey meaning.
although people can consciously change There are four categories of gestures: symbolic (or
their expressions to mask emotions. emblematic); deictic (or indexical); motor (or beat); and
lexical (or iconic). They might be used instead of speech
or alongside it for emphasis. Some scientists believe
that increasingly complex gestures evolved as the
forerunners of speech, which now defines our species.

DEFENSIVE TYPES OF GESTURES Symbolic
These are gestures that can be literally translated into
Posture words—for example, waving hello or making the “okay” sign.
An aggressive posture tends to inflate a person’s They are widely recognized in a given culture but may
size. It may involve extending the arms, setting not be recognized beyond that culture.
the feet far apart, and protruding the chest.
The same postures may be used to invade Deictic
others’ personal space. In contrast, defensive Deictic gestures involve pointing or otherwise
postures are closed—folded arms, for example, indicating a concrete object, person, or more intangible
are a classic indicator. item. Used with or without speech, they act like pronouns,
meaning “this” or “that.”

Motor
This type of gesture is short and tied to speech patterns,
such as moving the hand in time with speech, and is used for
emphasis. Motor gestures contain no inherent meaning and
are meaningless without accompanying vocalization.

Lexical
These gestures depict actions, people, or objects, such as
miming throwing when telling a story about throwing a ball,
or using your hands to depict an object’s size. They usually
accompany speech but contain meaning independently.

SIGN LANGUAGE Broca’s Motor cortex
area
Sign language may appear to
be a sophisticated type of Auditory area Wernicke’s area
body language, but it has
more in common with speech.
Studies show that when
people sign, the same brain
areas (see right) light up
as when they speak. Sign
language has grammar, and
each gesture has a specific
meaning, while body language
is interpreted broadly.

How to Tell if
Someone Is Lying

Separating truth from falsehood depends partly
on knowing a person, so you can judge whether they
are behaving differently from usual. With a confident
and persuasive talker, especially someone you don’t
know, how easy is it to spot a lie?

120 121

The short answer is, it is difficult. Clues from speech person’s total cooperation. Certain
Traditional telltale signs of lying parts of the brain are more active
are shifting gaze to avoid eye Speech can be slightly more reliable. when lying and show up together
contact, folding and unfolding arms, Hesitation, repeated words or on screen. These include the
shrugging shoulders, and fidgety phrases, breaking up sentences, prefrontal, parietal, and anterior
hands and feet. However, scientific a change in tone or in speaking cingulate cortices and the caudate
studies do not support these beliefs. speed, vagueness, and describing nucleus, thalamus, and amygdala.
Some honest people are generally trivial details while avoiding the
nervous and squirmy. In others, main topic—are all strategies to In summary:
these signs show someone is give the brain “time to think” and • Be very aware of judging
concentrating on being trustworthy. figure out which falsehood might be someone you don’t know well.
most believable. This is especially • Don’t rely on time-honored
Polygraph, or “lie detector,” true for persistent liars, who must signs such as fidgeting and
machines—which record pulse and access memory so as not to lack of eye contact.
breathing rates, blood pressure, and contradict themselves as their • Clues from speech, such
sweating—have a dubious history. multiple deceptions become ever as hesitation and repetition,
This is partly due to the stress of more tangled. can be slightly more reliable.
using them. Innocent but anxious • In many tests, a simple “gut
people can show up as deceitful, A more reliable method involves feeling” was as successful
while calm, skilled liars pass easily. the use of fMRI (see p.43), a as most other methods.
brain scan that requires the

Morality

Most people living in normal environments develop instinctive
senses of right and wrong. Morality seems to be in part hardwired,
arising from the conjunction of rationality and emotion.

Where do right and wrong come from? Moral judgment KEY
When we make decisions,
Social norms based on shared morals exist across all cultures, our emotions play a vital role. Rational
enabling social cohesion. When making moral decisions, two In order to weigh moral circuit
brain systems come into play: a “rational” system that effortfully matters, brain areas that
and explicitly weighs the pros and cons of possible actions; and are involved in emotional Emotional
a system that rapidly generates emotional, intuitive feelings of experience coordinate with circuit
right and wrong. Interactions between rationality and emotion areas that register facts and
are complex, but studying brain activity while people grapple consider possible actions
with moral dilemmas has identified the key areas involved. and consequences.

Parietal lobe Amygdala Dorsolateral
Involved in working memory prefrontal cortex
and cognitive control, this area This area integrates rational and
of the cortex provides information emotional information. It may
needed to help us perceive social also counteract the ventromedial
signals, to figure out others’ beliefs area to suppress emotional drives
and intentions—such as whether when dealing with complex moral
an act was aggressive or how a dilemmas that favor cognitive
solutions using memories
social context should
affect behavior. or other data.

Posterior superior EXTERNAL VIEW Ventromedial
temporal sulcus prefrontal cortex
Temporal pole This area is an important
This part of the cortex functions The temporal pole functions structure for allowing emotional
with the parietal lobe, providing in both social processing, such responses to influence rationalized
as face recognition and figuring moral decisions. In psychopaths,
information to guide moral out the mental states of others, connections between this region
intuition and attributing beliefs to and in emotional processing. It and both the amygdala and
may also help combine complex reward pathways are
others and integrating this data
with the potential outcomes of perceptual inputs with disrupted.
intuitive emotional
actions. It also helps assess responses.
whether a person is
lying.

122 123COMMUNICATION
Morality

Altruism PSYCHOPATHY MIMICKING
EMOTIONS
Altruism—when a person acts to benefit another Psychopaths can understand
at personal cost or risk—involves empathizing morality and can, therefore,
with another’s distress then acting to help. mimic normal social
It involves distinct processes. interactions. This means
Brain scans show that acting that while they behave
altruistically activates the heinously, they remain
reward pathways (see pp.112– hard to identify. The
113), reinforcing the behavior underlying cause may
and quelling emotional be a disconnect between
discomfort. Selflessness is brain regions linking logical
a distinguishing feature of decision-making and
human behavior and an emotion, leaving them
evolutionary enigma unable to grasp the fallout
given dangers to the altruist. from their behavior.

Posterior Nucleus Medial
cingulate cortex accumbens frontal gyrus
This region is active when our This region of the brain
environment changes and when is important for decision-
we are thinking about ourselves. It making and for choosing
may help assess the seriousness of between alternative potential
offenses and the appropriate actions. This is especially
response by acting as a hub for the case when there is
integrating intuitions about conflict between
the mental states of multiple options.

others.

SEEING SOMEONE INTERNAL VIEW CAN BRAIN
HURT BY ACCIDENT DAMAGE AFFECT
PRODUCES SIMILAR Orbitofrontal
BRAIN ACTIVITY prefrontal cortex MORALITY?
AS IF THE VIEWER Activated by watching morally
WAS HURT charged scenes, this area It depends on the area
THEMSELVES processes emotional stimuli. It aids affected. For example, damage
in representing just rewards and to regions that link emotion to
punishments for observed moral choice can cause people
behavior and in making
emotionally driven moral to make “coldhearted”
decisions.
choices.

Learning Learning to talk
a Language
Our innate preference for looking at faces helps
Unlike other species, humans have newborns focus attention on people talking to them.
a brain with regions dedicated Later, making eye contact and following gaze allows
to language. Babies are born ready them to connect the words they hear with what is
to learn language, acquiring it being talked about. As they learn new words, infants
through an interplay between these make “overextension” errors by using a single word
specialized areas of the brain and to label multiple things, for example, by using the
their own unique experiences. word “fly” to refer to anything small and dark.
To learn language, we also have
to interact with other people. Timeline of speech
The exact timescale for mastering language varies
from child to child, but all children progress through
the main stages in a similar order—from cooing and
babbling to first words and, ultimately, full sentences.

SPEAKING First consonants: Intonation
c and g added to sounds,

Cooing (vowels Laughter begins Babbling, e.g., plus more First true
only) from “ba-ba,” “ga-ga” consonants, e.g., spoken words
6 weeks (true syllables) “ma-ma,” “da-da”

(not words)

UNDERSTANDING Prefers sound Can distinguish Responds to Understands 10–12 months
of mother’s between vowel own name some common Understands
simple
voice sounds and words for
consonants objects or instructions, e.g.,
“give me the ball”
people

PREPARING Prefers looking Throat anatomy Babies start to Begins to 10–12 months
at faces changes to make follow their understand Left hemisphere
speech sounds of brain becomes
(from birth) possible (before caregiver’s gaze pointing specialized for
this, the need to and begin to link
the words they speech
breathe while
breastfeeding hear with the
prevents this) object they are

looking at

PREBIRTH UP TO 4 4 5 AROUND 6 BY 6–8 9–10 10–11

MONTHS 10–12

124 125COMMUNICATION

Learning a Language

The bilingual brain RIGHT White ALCOHOL AND LANGUAGE
HEMISPHERE matter
In the brain of a bilingual speaker, preserved One study of second-language learners
languages “compete” for attention. in older looked at whether alcoholic drinks would
This provides unconscious practice bilingual improve speaking and pronunciation by
in ignoring irrelevant information, adults reducing self-consciousness. It worked
and studies show that bilinguals up to a point—but after too many drinks,
are better at this than monolinguals. Activated performance rapidly deteriorated.
The ability to learn a second region
language like a native speaker is of gray LEFT BONJOUR, BHLEES
usually lost after around four years matter HEMISPHERE ÇA VA? CHIDEVSSSS
of age, especially with pronunciation.
The brains of elderly bilinguals Bilingualism areas
show better preservation of white Areas of gray matter (shown in
matter, which may protect them blue) are activated in bilingual
from the effects of cognitive decline. speakers when they switch
between languages.

One-word stage: Two-word stage “Telegraphic” Multiword, Vocabulary
can use single begins, e.g., stage of sentence-like commonly
words for speech begins: around 3,000
familiar objects, “mommy eat,” utterances of e.g., “shoe all words and
e.g., milk, cat, “daddy bad,” more than two wet.” Also use of growing. Also
cup “big teddy” “where,” “why,” increasing use
words. Also and inversion, of grammar, e.g.,
begins to use e.g., “where did plurals, past Full use
question words, of language—
(e.g., “where my you go?” tenses although many
book?”) and subtleties of
negatives (e.g., meaning remain
“no doing it”) to be mastered

May understand Can understand
around 50 around five

words. Becomes times as many
specialized in words as in
hearing speech speech
sounds within vocabulary
own language

Start to point for AT AROUND 18 MONTHS,
themselves, THERE IS A VOCABULARY
effectively EXPLOSION—THE WORD
“asking” for LEARNING RATE CLIMBS
word names TO ABOUT 40 A WEEK

AROUND 12 FROM 12 12–18 18 MONTHS 2 YEARS 2–21⁄2 3 ONWARD 5

YEARS

The Language
Areas

The human brain, unlike that of any other animal, Motor cortex
has areas dedicated specifically to language, usually The motor cortex enables the
located in its left hemisphere. The unique ability of physical movements required to
humans to communicate using language is thought produce language—for example,
to be an evolutionary advantage. moving your tongue, lips, and jaw.
The motor cortex is activated when
Broca’s and Wernicke’s areas words that are semantically related to
body parts are heard or spoken. For
example, the word “dance” might

be related to your feet.

The two main language areas are Broca’s and Wernicke’s areas.

Broca’s area is associated with moving the mouth to articulate

words. When learning new languages, separate parts of Broca’s

area are activated when we speak either our native or non-native

tongue. In Wernicke’s area, words that we hear or read are Speech travels through
understood and selected for articulation as speech. Damage to air as sound waves

this part of the brain can lead people to speak in peculiar ways,

creating sentences that do not make sense.

BRAIN DAMAGE AND HELLO
LANGUAGE CHANGES
SHWMAE BONJOUR
There have been cases in which
patients with brain injury appeared ASALAAM ALAIKUM
to wake up speaking a different
language or with a different accent. GUTEN TAG
Foreign accent syndrome is one PRIVET
example of such a medical OLÁ
condition. These cases are rare, and
there have not been sufficient KONNICHIWA
scientific studies carried out to
understand them in any detail. HOLA CIAO

#&@å Speaking and understanding
žøï¿œ Processing language is a complex task.
Articulating or decoding even a simple
»§ë greeting, such as “hello,” requires several
different areas of the brain to work together.

126 127COMMUNICATION

The Language Areas

MOTOR CORTEX Supramarginal Aphasia
UPRAMGAYRRGUISNAL gyrus
Aphasia is a medical condition
Although it is not considered in which people are unable to
one of the main language areas, comprehend or produce language,
read, or write due to damage
the supramarginal gyrus caused to the brain—for example,
works with the angular gyrus as the result of a trauma, stroke,
or tumor. The condition can be
to perceive and process relatively mild or severe. There are
language in order to give many types of aphasia (for some
examples, see table below). Some
words their meaning. are named after the brain area
that is affected or the type of
A speech produced. However,
aphasia can affect language,
BROCA’S S NGULAR GYRUS reading, and writing in many
AREA different ways, and some of these
difficulties may not fit into one
AUDITORY CORTEX WERNAIRCEKAE’S specific type or category.

TYPES OF APHASIA

Angular gyrus TYPE SYMPTOMS
The angular gyrus is associated
Global The most severe form of aphasia,
with complex language. causing general deficits in
It coordinates auditory, sensual, comprehension, understanding,
and visual information to help and production of language.
us understand words and concepts.
Broca’s Speech production is affected
The angular gyrus allows the and can be reduced to just a few
association of particular words words, which may be halting or
“nonfluent” in their nature.
with different images, ideas,
or sensations. Wernicke’s An inability to understand the
meaning of words. Speech
Auditory cortex production is unaffected, but
The auditory cortex is part of irrelevant words may be used,
the temporal lobe at the side of forming nonsensical phrases.
the brain. This area processes
auditory information in humans Anomic Difficulty finding words during
and other vertebrates to enable speaking or writing. This can
information to be heard. The auditory lead to vague language, causing
cortex is divided into sections (see significant frustration.
p.76), which allows humans
Primary Language capabilities become
to hear complex sounds, progressive slowly, progressively impaired.
such as words in This form can be caused by
a conversation. diseases such as dementia.

THERE ARE AROUND Conduction A rare form of aphasia that
6,500 DIFFERENT causes difficulty repeating
LANGUAGES SPOKEN phrases, particularly if phrases or
AROUND THE WORLD sentences are long and complex.

Facial expressions FACIAL SHRUG THINKING EMPHASIS EMPATHIC
We constantly use facial expressions RETELLING
during conversation. As speakers, we
raise eyebrows to emphasize a point WOULD
or indicate a question, and as listeners, YOU
we use expressions to show interest LIKE
in what is being said. One study looked
at the top reasons for using facial SYNTAX
expressions in conversation.

KEY Both
Speaker
Listener

QUESTION PERSONAL I’M LISTENING
REACTION

THE SPEAKER Message idea
The starting point of
1

a conversation is an idea the
speaker wants to express and
the intention to express it.
NO,
2 Formulation THANKS
The speaker selects the
words with the right meaning TURN TAKING

(semantics) and then puts them
into the right form and order
(syntax) to make sense. For LIKE
example, “Would you like a drink?” WOULD
is a question; “You would like a
drink” is a statement; and “Like YOU
you drink a would” is nonsense. SEMANTICS
Broca’s area (see p.126) is crucial
to these two processes.

3 Articulation
To say the message, the
speaker moves the mouth, tongue,
lips, and throat, controlled by the
motor cortex, to form the speech
sounds with the right intonation.

GARDEN PATH SENTENCES WOULD
YOU LIKE
We can be misled if the first part of a message suggests A DRINK?
an idea that is contradicted by the later part. For example:
“The car stopped at the crash scene was soon surrounded
by police.” We initially understand “stopped” to mean
something the car did; but when we hear “was soon,” it
becomes clear that the car was stopped by police. We
have to revisit the start of the message to make sense of
it. This type of statement is called a garden path sentence.

128 129COMMUNICATION

Having a Conversation

Having a Beyond words
Conversation
We constantly use nonverbal
A conversation is a shared endeavor between signals alongside speech in
speaker and listener, which involves more than conversation. In addition to adding
producing and understanding words. We take turns, emphasis (via facial expressions)
signal understanding, and align our thoughts. or visual effect (via gestures),
such signals allow the person
not speaking to have a role in
the conversation partnership,
encouraging the speaker without
interrupting or taking over.

4 Response THE LISTENER ELEMENTS OF CONVERSATION

Now the listener can reply Looking
and take their turn as speaker. Listeners look at their conversation
partner much more than speakers
3 Message interpretation do. They do this to show interest—
Usually, listeners add their as without this, speakers often
own experience to understand falter. In contrast, speakers look
the message. For example, if we intermittently at the listener.
are asked “Would you like a
drink?” at 9 a.m., we may expect Gestures
coffee, but at 9 p.m. it is likely the We use many types of hand gestures
offer is a different type of drink. (see p.119), including conventional
signs—such as “thumbs up,” pointing,
2 Message decoding and expressive hand movements—to
The listener recognizes words and add emphasis to the message.
makes sense of the message structure
WORD PARSING by analyzing the syntax (parsing). Parsing “I’m listening” signals
RECOGNITION Listeners use nonverbal sounds and
includes extracting meaning from the gestures, such as saying “mmm” or
order of the words. For example, “dog nodding, to show they are engaged in
bites man” has the same words but the conversation while not speaking.
different meaning to “man bites dog.”
Wernicke’s area (see p.126) is crucial in Turn taking
comprehending speech. Conversation requires taking turns,
and we start learning this from
1 Hearing speech sounds infancy. Conversation partners
The speaker’s speech rarely talk over each other, even
sounds are heard via the auditory though the average gap between
pathway in the listener’s brain. turns is only a few tenths of
a second.
Speaking and listening
PEOPLE TALK
Speaker and listener swap roles many times in a OVER EACH
conversation—and as speakers, we also monitor our own OTHER LESS
speech output. Although both roles involve multiple steps, THAN 5% OF
it can all happen fast—taking from 0.25 seconds between CONSERVATION TIME
having an idea to saying it, and from 0.5 seconds for
comprehension. Hesitation occurs when speakers need
time to “catch up” with the complex speech planning
and production process.

Learning to BIRTH ONWA RD AGE 3+
read and write
Babies imitate Children may
The ability to read and write sounds that start to recognize
is something that most people adults make symbols when
start to learn at a young age. playing
As our brains develop, we learn
important reading and writing 1 Making sounds 2 Recognizing symbols
skills. By the time we reach Babies make sounds that imitate Children begin to understand what
adulthood, we can read on average adults but often aren’t recognizable as words.
200 words per minute. Reading This is the foundation for learning to develop symbols mean when they are in text. They
requires several areas of the use the visual cortex and memory to
brain and body to work together. language skills. Babies see and process facial translate symbols that they see into sounds.
For example, when you read, your expressions using the visual cortex and other
eyes need to recognize the word areas. They then learn to associate sounds As children grow, they connect these sounds
on a page and your brain then with the meanings of words and start to
processes what that word says. and facial expressions with things in the world. relate language to written text.
Writing uses the brain’s language
areas (see pp.126–127), visual areas,
and motor areas concerned with
manual dexterity to make the
necessary hand movements.

Reading WHAT CAUSES
and Writing DYSLEXIA?

Our brains are hardwired for speech, but the Research suggests that children
ability to read and write is not innate. We have with dyslexia have problems
to start training our brains as babies to develop understanding the sounds
these complex skills. letters make, but dyslexia is
also found in cultures where
symbols represent an idea
rather than a sound.

DYSGRAPHIA

Dysgraphia is the inability to write tHisIsaS eNT EncEwriT SPEED READERS
clearly. It can be the symptom of tENbY sOMEonEwItHdYsGRapHiA ARE ABLE TO
some brain conditions, such as READ MORE
Parkinson’s disease, that affect fine THAN 700
motor skills. Writing may be wobbly WORDS PER
and indistinct or completely mangled. MINUTE

130 131COMMUNICATION

Reading and Writing

AGE 5+ AGE 11+ AGE 13+

Reading As fine motor We increasingly
to a child skills advance, read text on
helps them writing becomes screens and type
relate sounds more fluent words on
and text keyboards

3 Beginning to read 4 Expanding vocabulary 5 Continuing to learn
Reading aloud can improve a child’s As we grow older, we experience As adults, we continue to learn and
reading ability. Listening to a story activates more of the world around us so we learn and
the auditory cortex to hear the words, which see new things, adding to our vocabulary. practice our reading and writing skills. Our
vocabulary is constantly being extended.
are then processed by the frontal lobe. Comprehension, the ability to understand Learning to read and write is just the start
Picture books help children practice relating how to use words, requires every lobe of
words to images, and asking them to join in the brain (see p.30) and the cerebellum to of the story. The whole brain is required to
maintain language skills, and good brain
reading builds vocabulary and comprehension. successfully comprehend and use language. health is vital to both reading and writing.

Dyslexia Nondyslexic brain reading ALPHABETIC PRINCIPLE
Broca’s area helps form and articulate
Dyslexia takes various forms, speech. The parietal-temporal cortex works The alphabetic principle is the idea
affecting people’s ability to read or to analyze and understand new words. The that individual letters or groups of
write, or both. It is thought that up occipital-temporal area forms words and aids letters represent sounds when they
to one in five people have dyslexia. in meaning, spelling, and pronunciation. are spoken aloud. The alphabetic
A full neurological explanation of principle has two parts:
the causes of dyslexia has not yet Increased Less
been achieved. Studies have activity activity 1. Alphabetic understanding
suggested that particular Learning that words are made
structures of the brain function up of letters that represent the
differently in dyslexia (see right). sounds made when speaking
As children with dyslexia typically these letters aloud.
struggle with their reading abilities,
it is difficult to determine whether 2. Phonological recoding
the developing brain impacts the Understanding how strings of
dyslexia or if the dyslexia itself has letters in written words combine
an impact on the developing brain. to make sounds, which enables
spelling and pronunciation.

KEY Inferior frontal Dyslexic brain reading
Parietal-temporal gyrus (Broca’s Broca’s area is activated to form and articulate
area) words, but the parietal-temporal and occipital–
Occipital-temporal temporal areas are less active. Broca’s area
can be overactivated to compensate for the
lack of stimulation of the other regions.



MEMORY,
LEARNING,
AND THINKING

What Is Memory?

Our memory allows us to learn from experience and shapes us as
individuals. Memory is not a single discrete brain function; there
are several types, involving different brain areas and processes.

Memory in the brain Types of memories

Memory includes instinctive processes that you are unaware of, as To better understand how it works,
well as the more obvious parts that allow you to remember what you scientists break memory down into
had for lunch yesterday or your boss’s name. Each type of memory a number of types. Many of these
uses a range of different brain areas. Scientists used to think the rely on different networks within
hippocampus was vital for all new memories to form, but now it the brain, although there is also
is thought this is the case only for episodic memories. Other types a lot of overlap between the brain
of memories use other areas, which are spread all around the brain. areas involved in each category.

Caudate nucleus Frontal lobe is Cingulate cortex may Putamen
is associated with involved in working be involved in is involved
and episodic memory memory retrieval in learning
memories of procedural skills
instinctive skills
Parietal lobe is
Mammillary body important for
is involved in spatial memory

episodic memory Thalamus helps
direct attention
Olfactory bulb links Short-term
to the amygdala Hippocampus memory
so smells are turns experience
into episodic Short-term memory is very
potent triggers for memory limited—storing only around 5–9
emotional memories
Temporal lobe items, but this varies between
Brain areas Amygdala is vital for holds general individuals and for different types
Memory areas often relate to the forming emotional knowledge of information. To keep something
information stored. Memories of memories in short-term memory, we often
movement, for example, use the Cerebellum is
motor cortex. Limbic areas, linked to vital for “muscle repeat it to ourselves, but if we
emotion, are also involved in memory. memories” are distracted, we instantly
forget it.

Nonassociative Simple classical Priming and
learning conditioning perceptual learning
In priming experiments, you are
When you are repeatedly exposed Made famous by the Russian shown a word or picture so quickly
to the same stimulus, such as a light, physiologist Ivan Pavlov and his you don’t consciously “see” it—but
a sound, or a sensation, your response dogs, in classical conditioning, it can still affect your behavior.
changes. For example, when you come repetition causes something neutral to For example, someone primed with
home, you smell dinner cooking, but be linked with a response. An example the word “dog” will recognize the
gradually the smell seems to fade. is your mouth watering as you enter word “cat” faster than a
completely unrelated word
This is known as habituation, one a cinema lobby, as you have
form of nonassociative learned to expect popcorn in such as “tap.”
learning.
that environment.

134 135MEMORY, LEARNING, AND THINKING
What Is Memory?

Memory systems WORKING MEMORY 50 x 20
Memory is split into two main
types: short- and long-term To multiply 50 x 20, you must TO DO
memory. Short-term memories are manipulate the numbers stored
fleeting, but important information in short-term memory. This 5x 20 =100
can be passed over to long-term uses a process called working 100 x 10 =
memory for storage. Long-term memory. Working memory
memories may last a whole lifetime ability is one of the best 1,000
and are further divided into predictors of success in
school for young children. WORKING
several different types
of memories.

Long-term
memory
Our long-term memory allows us
to store a—theoretically—almost
infinite number of memories for most
of our life. Long-term memories are
stored as distributed networks of
neurons spread out across the outer
layer of the brain, the cortex.
Recalling the memory sparks
the network to fire again.

Nondeclarative Declarative
(implicit) (explicit)

Nondeclarative memories are Declarative memories can be told
unconscious so cannot be passed to someone else. They are conscious
from person to person using words.
You might try, for example, to explain and sometimes learned through
to someone how to tie their shoe repetition and effort, although others
laces or ride a bike, but they would can be stored without awareness of
the process. They include memories
probably still fail or fall off
the first time they attempted of events that have happened
in your life (episodic) and
to do it for themselves. facts (semantic).

Procedural Episodic Semantic
Skills or abilities, such as riding Episodic memories might be Semantic memories are
a bike or dancing, are termed recalling a big event like your 18th factual—meaning they are things
procedural memories. When first birthday or something mundane like that you know rather than things
learned, they require concentration yesterday’s breakfast. These are things that you remember. For example,
and conscious effort but over time you actually remember happening: these might include recalling the
they become habit. Often called recalling an episodic memory capital of France or the first three
“muscle memory,” procedural is almost like reliving the event. digits of Pi. Semantic memory relies
memories are actually stored The hippocampus is vital for on a large network of brain areas
and may not involve the
in a brain network involving storing new episodic
the cerebellum. memories. hippocampus at all.

How a
Memory Forms
MEMORY TRACES
When networks of neurons in the brain are
repeatedly activated, changes in the cells Scientists have recently been able to
strengthen their connections, making it easier pinpoint a precise memory trace in
for each to activate the next (see pp.26–27). This someone’s brain. In general, memories
process is known as long-term potentiation. tend to be stored near the area of the
brain that relates to how they were
formed. For example, memories for
voices would be near the language
centers, and things that you have
seen are stored, at least partly,
near the visual cortex.

Strengthening connections

When you repeatedly activate a group of neurons—by practicing a

skill or revising facts, for example—they begin to change. This is how AUDITORY
we form long-term memories (see p.135) in a process called long-term CORTEX

potentiation, which depends on various mechanisms taking place

in brain cells. The first (presynaptic) neuron makes more VISUAL
neurotransmitters release when the signal reaches it, and the second CORTEX
inserts more receptors into its membrane. This speeds up transmission
at the synapse. Something like driving a car, which seems complex Memories of sounds
when you start, can become effortless as the neural pathways involved are stored partly in or
near auditory cortex

become more efficient. If this paired activation is repeated enough, new

dendrites can grow, linking the two neurons via new synapses, giving

MORE THAN 100 DIFFERENTthe message alternative pathways and helping it travel even faster. LEARNINtrGaEvelelsctarliocanlgsaigxnoanl
of sending neuron
NEUROTRANSMITTERS BEFORE
HAVE BEEN IDENTIFIED
Action potential AXON
Nerve cell in triggers release of SYNAPS
hippocampus fires a neurotransmitter
signal to a receiving cell

E Vesicle containing
AXON neurotransmitters
NERVE CELL Second DENDRITE
BODY nerve cell

Firing together SYNAPSE
Long-term potentiation
occurs across the brain but 1 Before learning, only a weak connection exists between
has been best studied in the neurons. One action potential (pulse of electrical current)
hippocampus. Electrical signals from the first cell releases only a small amount of neurotransmitters,
travel along a neuron’s axon to and this may or may not be enough to activate the next neuron,
the synapse, where chemical which has just a few receptors.
messengers are released.

136 137MEMORY, LEARNING, AND THINKING
How a Memory Forms

Emotional memories KEY
Neurotransmitter
When something strongly emotional happens, whether that is good or bad,
stress chemicals such as adrenaline and noradrenaline are released. These Phosphate
make it easier for long-term potentiation to occur with fewer repetitions.
This explains why emotionally arousing memories are stored more rapidly
in the brain and why they are easier to recall than nonemotional memories.

Changes Action potential in
triggered in presynaptic neuron triggers
hippocampal
neurons neurotransmitter release

Noradrenaline Neurotransmitter
released by neurons released

in locus coeruleus, HIPPOCAMPUS Phosphates guide
located in pons LOCUS receptors to insert
themselves next to synapse
COERULEUS
1 Hormone released 2 Strong connection Neuron is
Noradrenaline released An enzyme adds primed for
by neurons originating in the PONS phosphate groups to receptors connection
locus coeruleus triggers a cascade in the postsynaptic neuron. This
of changes within cells in makes it easier for more receptors Action potential
the hippocampus. to be inserted in the cell membrane, triggered easily
so the connection is strengthened
and the memory forms easily.

EARNING mtRoeopbreeearnteeeldeuaraoscettrdiavnatsimonittcearusses ARNING More neurotransmitters
produced and
More released
receptors

move to
membrane

surface
DURING L
AFTER LE
Strong
connection

allows
signal to
pass quickly

More receptors
on receiving
cell

Action potential
triggered in

second neuron

2 Both neurons firing repeatedly at the same time causes a 3 Now, a single action potential causes the release of
chemical cascade within the second cell (see p.26), which more neurotransmitters, carrying the message quickly
and efficiently across the synapse, where it is received by
makes it more sensitive to the neurotransmitter, and causes extra many receptors. This makes it easier for the second neuron
receptors to migrate to the edge of the synapse. A signal travels
back to the first cell, telling it to produce more neurotransmitters. to be activated, sending its electrical signal onward.

Storing Memories CORTEX

After being encoded by the hippocampus, memories are PREFRONTAL CORTEX
consolidated and transferred to the cortex for long-term
storage. These memories are formed by strengthening
connections, a process called long-term potentiation
(see pp.136–137).

Storage in the cortex WHY DO I
FORGET WHERE I
To transfer memories for long-term LEFT MY KEYS?
storage, the hippocampus repeatedly
activates a network of connections Often, things we “forget”
in the cortex. Each activation actually weren’t stored
strengthens connections until they as memories in the first
are secure enough to store the place, because we weren’t
memory. It was thought that paying attention when
memories formed first in the
hippocampus, with the cortical we did them.
memory trace forming later, but
recent research in mice suggests Memory bank
that they may form simultaneously, Memories are stored as networks
although the cortical memory is of connections in the cortex. The
initially unstable. Repeated number of neurons here creates
reactivation of the network a near infinite amount of possible
somehow “matures” the cortical combinations—in theory, long-
memory, meaning we can use it. term memory is virtually unlimited.

Consolidation LEARNING CONSOLIDATION

This storage process, known as 1 Study 2 Sleep
consolidation, happens mainly When you learn something new, While you sleep, new
while we sleep. During this time, your brain takes in that information and information is consolidated. The
your brain is not processing forms new connections, or strengthens memory becomes less reliant on
information from the outside synapses that already exist. the hippocampus and less likely
world so it can carry out these to be affected by interference
housekeeping tasks. Memories from other inputs or brain injury.
are sorted, prioritized, and the
gist extracted. They are also
linked with older memories,
already in storage. This makes
it easier to retrieve important
memories in the future. Studies
have shown it is better to take a
nap after learning something
new than it is to keep studying!

138 139MEMORY, LEARNING, AND THINKING
Storing Memories

2 Memory stored in cortex A certain combination of
Networks across the cortex neurons fires repeatedly
store memories for things that to consolidate memory M

happened less recently. Different EMORY TRACE
types of memories might be stored
in various combinations of regions.

X
SOMATOSENSORY CORTE
COVIRSTUEAXLAUDITORY
CORTEX

HIPPOCAMPUS Synapses strengthen,
storing memory as
1 Memory encoded by hippocampus a trace
Experiences are registered by the
hippocampus, and some of them—those that are HIPPOCAMPAL
destined to become memories—are encoded INJURY CAN MAKE
there. Long-term potentiation alters connections FORMING NEW
between neurons in the hippocampus to create LONG-TERM
a memory. This area is vital for new memories. MEMORIES
IMPOSSIBLE
RETRIEVAL
PRACTICE MAKES PERFECT
3 Remember
When you wake up, the memory If you learn something just once, over time that memory
of what you learned is stored more trace will fade as the connections weaken. The more times
securely. It has also been linked to other you practice or revise something, the stronger those
facts, making it easier to recall, and you connections between neurons become and the more likely
may find that you you are to remember it in the future.
understand the
underlying KEY
concepts better. RestStrength of memory trace
Study

Time

Recalling a Memory Nerve-cell connection
activated during recall
Recalling a memory is not the passive process we once
thought, like playing back a recording on your phone.
Instead, our brain actively reconstructs our experience from
the information it has stored. This introduces the opportunity
for mistakes, meaning our memories can change over time.

1 Memory in the cortex
Each time we recall a
long-term memory, the network of
cortical neurons storing it is activated.
This strengthens the connections
between the cells, so it is less likely
Neuron in cortex

to be forgotten in the future.

Nerve-cell connection
strengthens

2 Strong connections Strong emotions Cortex
If we do not recall a memory make it easier for DATES
frequently, the connections between connections to
the cells will weaken and the memory strengthen
will fade. Memories associated with
strong emotions, however, are less STORED MEMORY

HOME LIF

E

likely to decay with time.

Reactivating a memory RELATIONSHIPS TRIPS
Stored memories
When we recall a memory, we activate Most memories are stored
the same network of neurons that long-term in the cortex, but
fired during the original experience, you can’t point to the area for
bringing it back to mind. While being your 18th birthday, for example.
recalled, the memory enters a flexible, Each memory is represented
or labile, state. This means that once by a network of neurons,
we have finished thinking about that spread across the brain.
memory, it must be reconsolidated
and stored again. If new information
is presented while the memory is
labile, it can be stored alongside old
information. This allows memories to
be changed and updated.

140 141MEMORY, LEARNING, AND THINKING
Recalling a Memory

False memories 1 True memory
Scientists asked participants to watch
When a memory is reconsolidated, clips of car accidents. After each clip, they had
new information is stored with old. to describe what happened and answer
But when we next recall the memory, questions. This meant they were recalling
it is impossible to tell which is which. and reactivating
This means we can end up with the memory.
false memories. Just talking about
an event can change our memory of
it, so in legal cases, witnesses must
be questioned carefully, to avoid
contaminating their memories.

WHAT IS 2 New information
DÉJÀ VU? Some participants were asked about the cars’
The feeling of déjà vu speed when they “contacted” each other, while
might arise because we others were asked about the speed when
recognize something in the cars “smashed.” The first group
an environment but cannot rated the cars as slower than
recall what. This gives the second group.
a vague feeling
of familiarity. TIME LATER NEW INFORMATION
STORED WITH OLD
VACATIONS
3 False memory recalled
One week later, subjects recalled the video again
and were asked whether there was any broken glass (there
was not). Significantly more people in the “smashed”
group “remembered” broken glass. The
words used had changed their
memory of the event.

BIRTHDAYS

RECALL VERSUS RECOGNITION

It is much easier to recognize something
as familiar when we are shown it than it
is to recall the details without any input.
For example, we all know what a quarter
looks like, but could you draw one
from memory?

How to Improve
Your Memory

Once we understand learning and recall, research
shows that we can find ways to boost these
processes and improve our memories. Some of the
best memory techniques, such as the memory
palace, are actually some of the oldest.

Often, when we “forget” external—such as the scent of
something, we haven’t stored it freesias taking you back to your
properly in the first place. To avoid wedding day. The memory palace
this, we must process information technique uses associations and
deeply—paying full attention to triggers to help recall long lists
what we are learning, thinking of information in order.
about it, and seeing how it links
to other things we already know. Probably the most important
thing we can do for our memories
Once stored, we need to make is get enough sleep. If we are tired,
sure the information stays put, by our focus and attention suffer, and
practicing or repeating whatever the brain just isn’t in the right state
we are trying to learn. The more to learn. Sleep is also vital after
often we activate pairs of neurons learning for memories to be
together, the stronger that consolidated, sorted, and stored.
connection becomes and the more
likely we are to remember it in the Here is a quick recap of how
future. The spacing of repetitions is to boost your memory:
important, too—it is better to revise • Process the information deeply.
for 10 minutes a day for six days • Rehearse it regularly.
than one hour on a single day. • Use cues and associations.
• Get plenty of sleep.

The power of cues and rest Using a memory palace
Imagine you are walking through somewhere
There are techniques we can use to familiar, such as your house. At strategic points,
help recall information, and many visualize objects relating to the words you
of them rely on cues. These triggers hope to remember, such as the items on a
can be internal, such as mnemonics, shopping list. To recall the list, simply “walk”
which provide the first letters of a the route again – the objects act as triggers.
list of items, cuing recall of the
items themselves. Or they can be

142 143

Why We Forget

There are many theories to explain why we forget things. Memory trace
Some scientists think that all our memories remain in our exists in brain;
brains but that we sometimes lose the ability to access them. often, blockage is
Our memories may also interfere with one another. later released and
memory can
Forgetting in the brain MEM ORY ORY be recalled
MEMY RECALL
There are many conditions that Memory cannot
cause us to forget (see pp.146–147). be accessed or
Broadly, there are two possibilities brought to mind,
for what happens in the brain when perhaps giving
we do. The simplest idea is that a “tip of the
over time memories fade away; tongue” feeling
information is lost as the trace that
was formed is no longer there. But MEMOR
evidence for this is hard to come by,
as other factors could be involved.
Most of us have experienced the
struggle to remember information
that later pops into your head for no
reason—this suggests memories
can still exist but be inaccessible.
This could be because other similar
memories are interfering with them,
or because there is no cue in our
environment to prompt that recall.
It is not known whether the
nerve-cell connections of a memory
disappear or if they still exist but
we are unable to access them.

WHY DO I FORGET Memory retrieved Failure to retrieve
WHAT I WENT When we recall If recall is unsuccessful, it
UPSTAIRS FOR? may be that the memory
something, we must
Leaving a room changes the reactivate the network is still in the cortex,
environmental cues that help of neurons that stores it. we are just unable to
access it (above). Or
us remember. When you If this is successful, connections may have
go back to where you were, we remember the been lost (see right).

the memory often fact or event.
reactivates.

144 145MEMORY, LEARNING, AND THINKING
Why We Forget

Interfering memories ACTIVE FORGETTING

Our brains experience interference, particularly when information Forgetting seems passive,
is similar. Learning new information can block recall for old, and but you can choose to forget.
old information can also affect new. These problems might arise In one study, subjects’
because the wrong memory trace is activated when you go to recall prefrontal cortices—involved
the information, blocking access to the right one. Or it may be that in suppression—were activated
old information can disrupt consolidation of new, and if successful, when they were told to forget
the new memory may actually replace the old one. a specific word.

Proactive BONJOUR, HOLA, Prefrontal
interference ÇA VA? ¿CÓMO cortex
Old memories may ESTÁS?
disrupt new ones. WE MAY BE LESS
For example, when LIKELY TO RECALL
starting to learn INFORMATION WE
Spanish, you may CAN FIND EASILY
experience interference ONLINE; THIS IS THE
from French words GOOGLE EFFECT
learned as a child.

Retroactive BONJOUR, HOLA,
interference ÇA VA? ¿CÓMO ESTÁS?
If you later went to
speak French and
instead spoke Spanish,
that would be new
memories disrupting
the recall of old ones.

ONTHS YEARS CADES
M
DE

1 Storage 2 Memory fades 3 Losing a memory
Long-term memories are stored If months or years pass before you One theory for forgetting is that
in the cortex as networks of connections. recall a memory, it may begin to fade. synapses that are not in use become weaker
These form and strengthen over weeks or Without reactivation, connections between and are eventually pruned away, taking that
months. Recalling a memory activates it, nerve cells are not strengthened. Specific memory with them. The longer a memory
strengthening the synapses and making details about special events, such as the food is inactive, the more likely it is to be lost
the memory easier to retrieve later. you ate at your wedding, may be forgotten. through this process.

Memory Retrograde amnesia
Problems People often forget moments before
an accident, but they can lose weeks,
Memory problems increase with age, and dementia or even years. Some memories,
affects one in six people over 80. Sometimes, brain especially older ones, return slowly.
damage, stress, or other factors can cause us to
experience an inability to remember (amnesia). Anterograde amnesia
People with anterograde amnesia are
Amnesia unable to form new memories. They
remember who they are and retain
If someone suffers a brain injury that damages the hippocampus and memories from before the damage.
surrounding areas, it can cause amnesia. There are two main types,
depending on whether the patient forgets memories they had stored Transient global amnesia
before the incident (retrograde amnesia) or is unable to form new This is a sudden episode of memory
memories (anterograde amnesia). There are also cases of amnesia loss, typically lasting a few hours.
without any obvious signs of damage, for example, after experiencing There are no other symptoms or
a psychological trauma. Drugs and alcohol can cause temporary obvious cause.
amnesia, although this can become permanent if large amounts are
used over a long period. It is also possible to suffer anterograde and Infantile amnesia
retrograde amnesia at once, particularly if there is significant damage Infantile amnesia refers to the fact
to the hippocampus. This condition is called global amnesia. that people usually cannot retrieve
memories of situations or events
before the age of two to four years.

Dissociative amnesia
This can be triggered by stress or
psychological trauma. Patients forget
days or weeks around the trauma or,
in rare “fugue states,” who they are.

Aging and memory BY THE TIME PEOPLE
REACH THEIR 80s, THEY
As we age, it is normal to experience memory MAY HAVE LOST AS MUCH
lapses and encounter more difficulty learning new AS 20 PERCENT OF THE
things. Focusing attention and ignoring distractions NERVE CONNECTIONS
becomes harder, and you may forget everyday IN THEIR HIPPOCAMPUS
things, such as why you went upstairs, more often.
These experiences differ from the symptoms of
dementia (see p.200), which can include getting lost
in your own house or forgetting a partner’s name.

1 Losing trust in memory 2 Using memory less 3 Memory getting worse
Older adults often begin Brain abilities are like muscles, getting Not exercising your memory can cause a
doubting their memories, seeing normal stronger with use. Writing things down or vicious cycle of cognitive decline. Encouraging
lapses as a sign of worsening abilities. looking them up instead of exercising your older adults to use their memory, by providing
This can lead them to rely on it less. memory could make it worse. feedback showing it still functions well, may help.

146 147MEMORY, LEARNING, AND THINKING
Memory Problems

A curious case FRONTAL LOBE WHAT IS
Henry Molaison (1926–2008) was HIPPO “SHELL SHOCK”?
an American assembly line worker CAMPUS
suffering from severe epileptic The expression was coined
seizures. In 1953, he underwent during World War I to describe
surgery to remove sections of his an effect thought to be caused
medial temporal lobe, including
both hippocampi, to treat severe by the sound of exploding
epilepsy. This controlled his shells. Soldiers were, in fact,
seizures, but he forgot several suffering from PTSD, brought
years before the surgery
and developed anterograde on by the trauma of war.
amnesia. He could retain new
declarative memories (see
p.135) only for a few seconds
but could learn new skills.

Large areas CERE
of medial temporal lobe BELLUM

removed from brain VIEW FROM BELOW
in each hemisphere

Other memory problems POST-TRAUMATIC STRESS
DISORDER
Many things affect memory, from short-term stress to life events,
such as having children. Memory changes can be linked to changes Normally when we store memories, the
in our neurochemistry. For example, cortisol is released when we emotion fades over time, so we recall past
worry and hormones surge in a pregnant woman around the time events without reliving them. In post-
of birth. Lifestyle changes such as sleep deprivation also play a role. traumatic stress disorder (PTSD), sufferers
fail to dissociate memory from emotion,
CAUSE EXPLANATION and intrusive memories bring the fear
Stress flooding back. These memories can be
Moderate, short-term stress can make it easier to form activated by sights or sounds, and often
Anxiety memories, but it becomes harder to recall facts you have the patient is unaware of their triggers.
already learned. This may explain why the feeling of “going
Depression blank” during an examination is so common.

“Baby brain” Long-term or chronic stress, such as is experienced
by people with anxiety disorders, can damage the
hippocampus and other memory structures of the brain,
causing memory problems.

Depression can impact the short-term memory and cause
people to have difficulty recalling details of events they have
experienced. Healthy people tend to remember positives
better than negatives. In depression, this is reversed.

Pregnant women may experience mild decline in a range of
cognitive abilities, although these are likely to be noticeable
only to the women themselves. After the baby is born, sleep
deprivation can worsen memory problems.

Special Types Posterior hippocampus,
of Memories involved in spatial navigation

Although a few children exhibit remarkable skills,
most people with exceptional memory are not born
that way. Instead, they use special techniques and
lots of practice, sometimes leading to physical
changes in their brains.

Training exceptional memories Hippocampal Anterior
structures hippocampus
Scientists studying trainee London taxi drivers as they Our two hippocampi—
learned “the Knowledge” (a huge network of roads and one on each side of
landmarks) found that the volume of the subjects’ the brain—are vital for
posterior hippocampi increased as their ability to learning and memory.
navigate improved. This could occur due to the birth They can be divided
of new neurons or the growth of existing dendrites (see into posterior (back)
p.20). However, the taxi drivers performed worse than and anterior (front),
control subjects in memory tests not involving London with the posterior portion
landmarks. This suggests memory is finite, and particularly important for
improving one area may come at the expense of others. spatial navigation.

Savant syndrome ALL SA VANTS FLASHBULB MEMORIES
10%
People with mental disabilities People often remember where
sometimes demonstrate incredible ACQUIRED they were when receiving
abilities in one specific area, often CONGENITAL emotional news, and the memory
related to memory. This is called seems extremely vivid and
savant syndrome. Many savants are 90% detailed. These are called flashbulb
autistic, but the syndrome can also memories. However, studies have
be triggered by severe head trauma. AVANTS shown that we are as likely to be
Some savants can calculate the day 21% mistaken about these snapshots as
of the week for any given date. we are about any other memories.
Others remember everything they FEMALE
read or can paint detailed pictures CONGENITAL S
of scenes they have seen only once. MALE
Scientists think these talents may 79%
develop because of savants’ By genetics and gender
extreme focus and interest in one One database of savants, as reported by their
area. There is also evidence they parents or caregivers, found that the vast
see the world as building blocks, majority (90 percent) are born with the
not whole pictures, by accessing condition, and of these, most were male.
perceptual information most of us
are not consciously aware of.

148 149MEMORY, LEARNING, AND THINKING
Special Types of Memories

KEY Taxi driver’s posterior Posterior hippocampus Posterior hippocampus
hippocampus increases in volume returns to original size
Taxi driver’s
hippocampus

Before training, taxi drivers
have hippocampi with
regions of normal size

1 Same size 2 Changing anatomy 3 Returning to normal
At the start of the study, scientists The trainee taxi drivers who passed The brains of retired taxi drivers look
scanned the brains of the participants to “the Knowledge” had larger posterior much more like those of the control group.
measure the size of their hippocampi. There hippocampi than the control group, or the This suggests that the changes to the
were no differences between the trainee taxi trainees who failed. Some studies found that hippocampus revert once taxi drivers stop
drivers and the control group. the front of their hippocampi was smaller. using “the Knowledge” on a daily basis.

“Photographic” memory CAN PEOPLE
REMEMBER
There is no such thing as photographic memory—no one can literally EVERYTHING?
recall pages of text or images as if they were really in front of them. The
closest is eidetic memory, which occurs in 2–10 percent of children. After A perfect memory does
looking at an image, “eidetikers” continue to “see” it in their visual field, not exist, but a few people
until it gradually fades or disappears as they blink. have superior autobiographical

Picture imperfect memory, giving them
Studies have shown that eidetic images are not exceptional recall for
perfect. Children may not manage to remember
all the letters in a word they were shown, or events during
they may invent details, for example, “recalling” their lives.
something in a picture that was not really there.

MEMORY PEOPLE WITH
INCREDIBLE RECALL
Sometimes, people FOR FACES ARE
with an eidetic memory CALLED SUPER
vividly recall details that RECOGNIZERS
were not present in the

original scene, such as
the color of this roof

PHOTOGRAPH CHILD

Intelligence Network implicated
in hypothesis testing—an
There are many theories about how intelligence
evolved, what it actually constitutes, and which integral component
factors are key to high intelligence. of intelligence

What is intelligence? 1 Acquire Frontal lobe houses
Information large-scale networks
Intelligence is our ability to acquire is gathered through
information from our surroundings, various experiences, associated with
incorporate that information into understood, and intelligence
a knowledge base, and then apply retained for
it to new situations and contexts. processing. Theories of intelligence
While there are many models for Some studies suggest that connectivity
how human intelligence evolved, 2 Process between the prefrontal and parietal cortices
language and social living New and small areas of neurons (networks) is the
undoubtedly played a role as this information is key to high intelligence (above). Other
enabled knowledge to be passed critically analyzed, explanations (right) have also been put
on from generation to generation. compared with forward, suggesting that intelligence is related
The evolution of human intelligence existing knowledge to connectivity across the brain as a whole.
has led to our success as a species, and placed in context.
enabling us to adapt to and inhabit
almost all environments on Earth.

THERE ARE OVER 3 Apply
1,000 HUMAN Existing
GENES THAT knowledge is applied
HAVE BEEN LINKED to a new situation or
TO INTELLIGENCE problem, as opposed
to being repeated
from memory.

Types of intelligences Naturalist Existential
Recognizes features of plants Uses observations, insight,
Intelligence is often spoken of in a and animals and infers insights and knowledge to explain the
broad sense, but there is a theory based on what is known about external world and the role
that multiple intelligences exist. the natural world. of humans in it.
It recognizes that people may have
the capacity to acquire and apply Musical Interpersonal
knowledge in specific areas. For Sensitive to rhythm, pitch, Sensitive to people’s moods,
example, someone may struggle tone, melody, and timbre and feelings, and motivations.
with solving math problems but applies this to playing and Applies this to relationships
can reproduce a piece of music after composing music. and helping groups function.
hearing it only once. Some argue
this theory supports a more Logical–mathematical Bodily–kinesthetic
realistic definition of intelligence, Quick with numbers and easily Uses heightened body
while critics claim that these quantifies things. Figures out awareness, coordination,
“intelligences” are merely aptitudes. problems systematically and and timing to master physical
thinks critically about issues. activities such as sports.