Typographical support for dyslexics - Bureau ICE

Typographical support for dyslexics

The effect of textual alterations
on dyslexics’ test scores

A. E. Schoonewelle
VU University, Amsterdam
Faculty of Arts
Applied Linguistics
Master’s thesis

Supervisors:
Dr. P. H. F. Bos, VU University
Prof. dr. M. M. R. Coene, VU University
Dr. R. van Veen, Bureau ICE
Dr. M. Pit, Bureau ICE

Declaration of originality

I hereby declare that this dissertation is an original piece of work, written by myself alone. Any information and ideas
from other sources are fully acknowledged in the text and notes.

Amsterdam, June 2013

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 1

Acknowledgements

This thesis could not have been written without the help and support of a number of people, whom I would like to
thank here.

First of all, the schools in the The Hague/Voorburg region that participated in the experiment, especially the
students and the school’s coordinators who made it possible to set up, organise and carry out the experiment. The
experiment could not have taken place without their help.

I would like to thank my supervisors and colleagues at Bureau ICE. They contributed to this thesis by helping
me setting up the experiment’s design and selecting the schools, as well as offering technical support in the process
of developing the experiment’s software.

Special thanks to my family, friends, flatmates and fellow students who were there to listen to me, who
supported me when I needed it and who advised me what steps to take along the way. Your patience and
understanding have been great.

Last but certainly not least, a word of gratitude to my supervisor Petra Bos. I could not have done this
without her support, guidance and critical view whenever I asked her to reflect her thoughts on a subject. Thank you
for the comprehensive and quick replies to my questions, which is much appreciated. Finally, thank you for your
commitment and the time and effort you dedicate to all of your students.

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 2

Table of contents

Abstract …………………………………………………………………………………………………………………………5

Samenvatting (Dutch summary) ……………………………………………………………………………………………. 6

1 Introduction …………………………………………………………………………………………………………………..7

2 Background …………………………………………………………………………………………………………………. 8
2.1 Laws and regulations ………………………………………………………………………………………… 8
2.2 ICT support ……………………………………………………………………………………………………. 10

3 Theory ……………………………..…………………………………………………………………………………………13
3.1 Historical account of reading theories……..………………………………………………………………...13
3.2 Theoretical perspectives ……………………………………………………………………………………...14
3.2.1 Explaining dyslexia ……………………………………………………………………………… 14
3.2.1.1 Neurological and cognitive theories ………………………………………………14
Phonological deficit hypothesis ………………………………………………… 15
Double-deficit hypothesis ……………………………………………..………… 16
Rapid auditory processing hypothesis ………………………………………… 18
Visual deficit hypothesis ………………………………………………………… 19
Cerebellar deficit hypothesis ……………………………………...................... 19
Magnocellular theory …………………………………………………................ 20
Noise-exclusion hypothesis ……………………………………………………...22
3.2.1.2 Comorbidity …………………………………………………………………………. 23
3.2.1.3 Evolutionary theory ………………………………………………………………… 24
3.2.1.4 Genetics …………………………………………………………………………….. 24
3.2.1.5 Side effects …………………………………………………………………………. 25
3.2.2 Facilitating dyslexia / Typographical effects …………………………………………………. 26
3.2.2.1 Font type ……………………………………………………………………………. 27
3.2.2.2 Font size …………………………………………………………………………….. 32
3.2.2.3 Spacing ……………………………………………………………………………… 33
3.2.2.4 Contrast and colour ………………………………………………………………... 35
3.2.3 Summary of theoretical perspectives …………………………………………………………. 37

4 The experiment ………………………………………………………………………………………..…………………… 39
Research question …………………………………………………………………………………………………39
Hypotheses ………………………………………………………………………………………………………… 39
4.1 Participants ……………………………………………………………………………………………………..39
4.2 Material and design …………………………………………………………………………………………...39
4.3 Procedure ……………………………………………………………………………………………………… 40
4.4 Analysis …………………………………………………………………………………………………………40

5 Results ………………………………………………………………………………………………………………………. 41
5.1 Results of the experiment …………………………………………………………………………………….41

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 3

5.2 Results of the questionnaire ……………………………………………………………………………….... 41

6 Discussion and conclusion ………………………………………………………………………………………………...43
6.1 The experiment ……………………………………………………………………………………………….. 43
6.2 The questionnaire …………………………………………………………………………………………….. 44
Recommendations ………………………………………………………………………………………………… 48

Bibliography …………………………………………………………………………………………………………………… 49

Appendix I: Test Nederlands Lezen 2F toets 1 (Dutch Reading 2F test 1), normal test condition ………………… 54

Appendix II: Test Nederlands Lezen 2F toets 1 (Dutch Reading 2F test 1), experimental test condition ………….55

Appendix III: Questionnaire …………………………………………………………………………………………………. 56

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 4

Abstract

Font size, interletter spacing and interline spacing were increased in an experiment testing typographical alterations
facilitating dyslexics. The objective of this study was to test whether dyslexics benefit from these textual alterations.
Another aim was to provide an overview of theories regarding the nature of dyslexia, an overview of theories regarding
facilitative measures for dyslexics, and a background on current ICT facilities for dyslexics and on laws and
regulations. Both a qualitative method and a quantitative method were applied: Thirty-eight dyslexic students from two
secondary schools participated in the experiment, consisting of a reading comprehension test in a web-based testing
environment and a questionnaire. The participants were divided into two groups: a control group, taking the test in the
default setting, and an experimental group, taking the test in an experimental setting for which textual alterations were
applied. No significant difference was found between the groups. However, the questionnaire’s results indicated that
the participants preferred the experimental setting over the default setting. The main conclusion was that it is
recommended to keep the textual alterations as an option in the web-based environment.

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Samenvatting (Dutch summary)

In een onderzoek naar typografische aanpassingen voor dyslectici zijn lettergrootte, letterspatiëring (tekenafstand) en
regelafstand vergroot. Het doel van dit onderzoek was om te testen of dyslectici baat hebben bij deze tekstuele
aanpassingen. Andere doelen waren het geven van een literatuuroverzicht van theorieën over de aard van dyslexie,
een overzicht van theorieën wat betreft de faciliterende maatregelen voor dyslectici en het verstrekken van
achtergrondinformatie over de huidige ICT-faciliteiten en wet- en regelgeving voor dyslectici. Aan bod kwamen zowel
een kwalitatieve als een kwantitatieve methode: achtendertig dyslectische leerlingen van twee middelbare scholen
namen deel aan het experiment, dat bestond uit een toets begrijpend lezen in een web-based toetsomgeving en een
vragenlijst. De participanten werden verdeeld in twee groepen: een controlegroep die de toets in de normale setting
maakte, en een experimentele groep die de tekst in de experimentele setting maakte waarbij de tekstuele
aanpassingen waren doorgevoerd. Er werd geen significant verschil gevonden tussen de groepen. Uit de resultaten
van de vragenlijst bleek echter dat de participanten de voorkeur gaven aan de experimentele setting boven de
normale setting. De belangrijkste conclusie is dat het wordt aanbevolen om de tekstuele aanpassingen in de web-
based toetsomgeving aan te blijven bieden als optie.

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1 Introduction

Ever since humans began to read, reading has been a problem for some of them (Shaywitz & Shaywitz, 2008). The
concept of dyslexia was first described as ‘wordblindness’ by Kussmaul in 1877 (Stein & Walsh, 1997). In 1925,
Samuel Orton called the reading-related problem strephosymbolia, meaning as much as ‘twisted signs’ (Stein &
Walsh, 1997). The term ‘dyslexia’ was first introduced by Rudolf Berlin in 1887 (Wagner, 1973).

Today, dyslexia is commonly defined as a persistent reading and spelling problem which manifests itself in word
identification and language comprehension (Masterplan Dyslexie, 2005; Shaywitz & Shaywitz, 2008; Stichting Dyslexie
Nederland, 2008; Vellutino, Fletcher, Snowling & Scanlon, 2004). Vellutino et al. also describe it as a basic deficit in
learning to decode print (2004). The term ‘dyslexia’ is used interchangeably with ‘(specific) reading retardation’
(Ramus et al., 2003; Snowling, 1998) and ‘(specific) reading disability’ (Stanovich, 1988; Stein & Walsh, 1997; Wolf &
Bowers, 1999). An important characteristic of dyslexia is that it is a “discrepancy between reading ability and
intelligence in children receiving adequate reading tuition” (Ramus et al., 2003, p. 841), and therefore unrelated to IQ.
Dyslexia is a problem that does not only manifest itself in language education, but in all forms of education where
reading or writing is concerned. It exerts a great influence on dyslexics’ scores and test results and is therefore a
problem that needs remediation, facilitation or, ideally, recovery. Unfortunately, the latter is not (yet) in our range of
possibilities, which leaves remediation and facilitation.

This thesis is focused on the facilitative part of dyslexia. It is composed of an extensive literature review of leading
theories in dyslexia research and facilitating measures in dyslexia research. An experiment was set up and carried
out, based on the most recent and important findings in literature. This experiment took place in a practical and
meaningful setting of the Toolkit for the Education and Employment Market, hereinafter referred to as TOA (Toolkit
Onderwijs en Arbeidsmarkt). The TOA is a digital test system containing all kinds of tests to measure language
proficiency, math proficiency and many other skills, qualifications and competences. These tests, approved by the
Dutch Inspectorate of Education, are available for secondary education, vocational education, higher education,
integration and reintegration, companies, ministries and municipalities. The TOA is developed by Bureau ICE, a
company specialised in developing tests and exams, but also questionnaires, competence scans, assessments and
other measurement instruments.

Over time, Bureau ICE’s helpdesk has been receiving an increasing number of questions related to dyslexia. Most of
these inquiries involved questions about extra test time, zoom functions or text-to-speech software. The possibilities
and facilities that modern ICT provides are developing rapidly; besides, there is a growing need for facilities for
dyslexics among Bureau ICE’s customers. In this thesis it is investigated to what extent facilitative measures,
typographical measures in particular, are able to aid dyslexics in web-based testing in the TOA.

The goals of this thesis are 1) to provide a background on current ICT facilities for dyslexics and on laws and
regulations regarding dyslexia; 2) to provide an overview of theories regarding the nature of dyslexia; 3) to provide an
overview of theories regarding facilitative measures for dyslexia; and 4) to test whether dyslexics benefit from these
measures when they are applied in the TOA.

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2 Background

Before turning to the main theories regarding dyslexia in an explanatory and facilitative way, some practical
background is presented in order to provide a complete picture of dyslexia’s current position in the Netherlands.
Moreover, in order to construct an experiment to what kind of supporting technical facilities are needed, it is necessary
to know what legal regulations exist, what rights dyslexics have and what kind of facilities already exist. This chapter
focuses on Dutch laws and regulations and today’s ICT resources designed to support dyslexics.

2.1 Laws and regulations
In 2004, the Protocol Dyslexie Voortgezet Onderwijs (Protocol Dyslexia Secondary Education) was introduced, a
protocol developed to support schools in how to appropriately deal with dyslexia (KPC Groep, 2004). There are other
protocols for other levels of education as well, such as vocational education and higher education, but this particular
protocol is the most extensive of all and on top of that, the experiment in this thesis will be carried out in secondary
schools, which is why the focus will be on this particular protocol.

The most significant statements of the protocol are the following:
- Integrated approach: support in the classroom as much as possible. The most important factors of learning-
to-read-success are quality education and quality teachers;
- Economical principle: maximum effectiveness with minimum effort;
- Support during entire school time: not just intervention in the first year. Support measures like extra test time,
occasional oral exams, alternative spelling assessment, etc. should be available to everyone;
- Raising awareness and sharing responsibility among dyslexics and teachers, establishing a student-centred
policy: What is the student’s viewpoint? What kind of intervention has the student already had? What is the
teacher’s viewpoint? How can the effect of dyslexia in overall development be reduced to a minimum?
- Successful intervention and support is about adopting a positive attitude;
- Establishing a clear vision and policy of dyslexia support.

In 2012, the Dutch Ministry of Education, Culture and Science commissioned the Dutch Inspectorate of Education to
carry out a thorough study of the implementation of the protocol (Inspectie van het Onderwijs, 2012). Common
findings from their report are that special care is especially provided outside the classroom and, generally, teachers do
not play an active role in supporting their dyslexic pupils. On the other hand, all schools do have some kind of policy,
but only for incidental and organised care. Incidental care and organised care are the two lowest levels of the care
system out of the four levels described in the protocol, namely 1) incidental care, 2) organised care, 3) integrated care
and 4) integrated chain care (KPC Groep, 2004). Incidental care only takes place outside the classroom. There is only
ad hoc supervision and the teachers are merely informed about the student’s dyslexia. Organised care is also
separated from education, but works according to a supervision plan and is part of a care system. When it comes to
integrated care, teachers and supervisors work together to make care an integral part of pedagogical-didactic actions
by developing a shared supervision plan. Finally, in integrated chain care, care is also part of pedagogical-didactic
actions and on top of that, teachers and supervisors maintain an intensive cooperation with external organisations.

Only six out of the sixteen schools the Dutch Inspectorate of Education examined held a vision with regard to dyslexia;
one of the protocol’s bullet points. The inspectorate further distinguishes between vmbo (‘voorbereidend middelbaar
beroepsonderwijs’, literal translation ‘preparatory middle-level vocational education’) and havo/vwo (‘hoger algemeen

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voortgezet onderwijs/voorbereidend wetenschappelijk onderwijs’, literal translation ‘higher general secondary
education/pre-university education’).

The second level of the care system described above applies to most vmbo schools, meaning there is
organised care, but dyslexia support is separated from regular education. In most cases, a mentor or dyslexia coach is
available to provide support for dyslexics. Furthermore, there are supporting technical facilities inside the classroom
such as Kurzweil, Sprint or a Daisy player (see paragraph 2.2), but remediation takes place outside the classroom.
There is no supervision plan involving the teachers, which the protocol does advise.

Four out of eight of the examined havo/vwo schools have an organised care system like the vmbo schools.
The other four have an incidental care system, meaning that the pupil has to indicate his/her own needs and point out
what kind of facilitative measures are needed.

The Dutch Inspectorate of Education concludes that only the two lowest levels of the care system are offered in
schools. Professionalisation of dyslexia support among teachers, such as extra courses or contact with external care
institutions, is only optional and non-committal. There are no major differences when it comes to type of education or
school size, and there are few between-school partnerships regarding dyslexia.

All dyslexics of the sixteen schools examined have a ‘dyslexia declaration’, a document stating they have
officially been diagnosed with dyslexia. However, for most of the dyslexics, no specification was available and as a
result, no custom-made supporting facilities could be specified. Based on their dyslexia declaration, the dyslexics
received extra test time, tests printed in a larger font size, alternative spelling assessment and occasional oral
examination. Dyslexics may receive dispensation from learning a second modern foreign language, English being the
first modern foreign language, as stated in the Secondary School Act (Wet op het voortgezet onderwijs, 1963).
However, oral examination or alternative assessments are not a possibility at the final examination, the central exams.

Although the current situation appears to be insufficient based on the inspectorate’s examination, the inspectorate’s
final conclusion seems to be in contradiction with the recommendations in the protocol. They conclude by stating that
the sixteen schools do pay attention to dyslexia and try to offer the dyslexics an adequate amount of support, which
can be translated into offering them a fair chance of succeeding.

A similar, exploratory study commissioned by the Dutch Ministry of Education, Culture and Science was carried out in
2011. In that same year, the ministry introduced more stringent examination requirements (Examenblad, 2011). In a
formal reaction to parliamentary questions about the exploratory study, the former Minister of Education, Culture and
Science states that there is no reason to believe that schools operate inadequately when it comes to supporting
dyslexics (Tweede Kamer der Staten-Generaal, 2012). Like the 2012 report implies (Inspectie van het Onderwijs,
2012), the minister states that schools offer sufficient support systems to provide dyslexics with the same chance to
succeed as non-dyslexics.

In reply to parliamentary questions, the minister states that the percentage of dyslexics in secondary
education in 2011 is as follows: vmbo 15%, havo 11% and vwo 6%. The minister believes there is no relation between
dyslexia and intelligence, but dyslexics may be receiving education on a lower level because of their reading
problems. This contradiction is not further dealt with by the minister, but will be addressed in the theoretical part of this
thesis. All in all, the minister’s opinion is that dyslexics are sufficiently supported and that schools are performing
adequately in establishing equal chances for dyslexics and non-dyslexics in terms of examination (Tweede Kamer der
Staten-Generaal, 2012).

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2.2 ICT support
Supporting dyslexics with ICT applications is already happening on a large scale. There are several organisations and
institutions exclusively involved in designing and developing software and technology, especially for the reading-
impaired or -disabled. Opdidakt Supplies is a Dutch company developing support tools for dyslexics, and is specialised
in training educational institutions and companies on how to use these tools. In their brochure, they describe the many
advantages ICT tools provide. ICT tools provide a chance for dyslexics to be the best they can be, to receive
education at an appropriate level, it increases their independence and their competence (Opdidakt Supplies, 2012).
Furthermore, it is important that the tools are customised for the dyslexic in question. Lexima, a Dutch company
specialised in ICT solutions for reading- and learning problems, established some principles ICT tools should meet
(Lexima, 2012):

- ICT tools support both reading and spelling;
- The read-out word and the sentence are made visible with a (double) marker to stimulate actively reading

along;
- There is a variety of reading voices, reading speed and languages, and navigation is enabled throughout the

text;
- ICT tools support reading comprehension;
- ICT tools help developing study skills;
- Content is appropriate and compatible;
- ICT tools fit into learning trajectories for primary, secondary and vocational education.

Products meeting these criteria are developed by commercial companies such as Opdidakt or Lexima in the
Netherlands and Texthelp in the United Kingdom and the United States. Several (Dutch) ICT tools and their features
are described below.

Kurzweil 3000
The Kurzweil 3000 reads out several kinds of files, such as scanned texts, pdf, word, txt or rtf files, e-mails, internet
texts and other digital files. While reading out (text-to-speech), Kurzweil marks the read-out word, sentence or
paragraph. This stimulates dyslexics to actively read along.

Sprint
The Sprint software consists of a toolbar that is applicable to Word, pdf and internet browsers. Unlike the Kurzweil
3000, texts do not need to be transferred or converted to a special browser, but can be scanned and read out from
their own environment. One of Sprint’s features is a marker, which allows the reader to mark words or lines in the text.
After marking, Sprint makes a summary of the marked text. Another feature of Sprint is the option to save a text to an
mp3-format.

Sprint consists of multiple products:
- Sprint NL: This is the most basic product. It contains one language, Dutch, with several reading voices.
There is no dictionary or OCR-software (optical character recognition software) included, although it is
possible to upgrade Sprint with SprintOCR. Sprint NL works with a word predictor named ‘Skippy’, a word
predictor containing 24,000 words in each of the languages Dutch, English, French and German. In Sprint
NL, Skippy only supports Dutch.
- Sprint NL/EN: Sprint NL/EN is the extended version of Sprint NL. Needless to say, it does not only support
Dutch texts, but English texts as well. In addition to its Dutch-only counterpart, Sprint NL/EN does have a

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dictionary installed. Word predictor Skippy supports both Dutch and English. The remaining aspects are
comparable to Sprint NL.
- Sprint Plus: This most complete version of Sprint contains four languages: Dutch, English, French and
German. Word predictor Skippy supports these four languages and on top of that, Sprint Plus has
dictionaries installed for all four languages. Reading voices are available in these languages as well. Sprint
Plus has a spelling check called ‘Primus’, which is designed to correct mistakes known to be common to
dyslexics.

WoDy
This is a different kind of software that is designed for writing, but which also contains a reading-out function.
However, WoDy’s main purpose is not to read out, but to predict text while writing. The predictor is designed for
dyslexics, meaning that mistakes often made by dyslexics are anticipated and corrected.

Dragon Naturally Speaking
Dragon Naturally Speaking is a dictation program. Based on speech recognition, it converts speech to text. This
software is recommended to be used in combination with WoDy.

Ginger Premium
Ginger Premium is a grammatical spell check for English. Like WoDy, it is designed for dyslexics; it detects mistakes
known to be common to dyslexics and suggests alternative spellings. It also contains a text-to-speech function.

AppWriter NL
This app, designed for iPad, facilitates both reading and writing. It contains four languages with accompanying reading
voices. While reading out, the text is being marked, stimulating actively reading along. AppWriter NL also contains
OCR-software and the text processor works with the font Dyslexie, a font especially designed for dyslexics (see
paragraph 3.2.2.1).

BrowseAloud Plus
This is a reading tool for web-based content and is also compatible with smartphones and tablets. It is recommended
for e-learning and online testing. BrowseAloud enables the user to alter pronunciation of text, thereby allowing the
content to be customised. There are many languages and several reading voices available per language.

ClaroRead
ClaroRead is software which provides support in writing, reading, checking and correcting texts. It is a toolbar,
meaning the text does not have to be transferred to a different program or browser. The standard software contains
four languages: Dutch, English, French and German, with a possibility of adding other languages. There are twenty
additional languages available. Many of ClaroRead’s features are adjustable, such as reading voice, reading speed
and using a reading-along cursor. ClaroRead pronounces the words or sentences after they have been written. All
versions of ClaroRead include an optional word predictor, supporting the four languages mentioned before.

ClaroSpeak
ClaroSpeak’s features are similar to those of ClaroRead, but ClaroSpeak is an app especially designed for iPhone,
iPod Touch and iPad.

L2S

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L2S is originally a Scandinavian tool, but it has been adapted to Dutch, taking into account grammatical rules,
common mistakes and vocabulary lists. It is a reading-out tool, able to read out several kinds of files, such as
Microsoft Office (including Word), pdf and internet texts. It contains scanning software. The cursor moves along while
reading, stimulating actively reading along. This software is also meant as a tool for writing; it reads out text
immediately after it has been written. Another function is to convert texts to mp3 or other audio formats.

Easy Tutor
This is text-to-speech software which supports Microsoft Office, internet and pdf. Besides reading out, Easy Tutor also
highlights the read-out text by marking it and by applying extra spacing. It contains dictionaries in Dutch, English,
French and German.

BrowseAloud Plus
This text-to-speech software is web-based and highlights the text while reading out. The speech sounds relatively
natural and also takes into account intonation and prosody. The software is highly adjustable and the reading-out
function can be turned on and off on different parts of the website it is applied to.

ReadSpeaker
Another kind of text-to-speech software that contains more than 35 languages. ReadSpeaker is web-based and works
on all devices and browsers. It also highlights the text while reading out and is user-friendly.

DAISY player
Finally, the DAISY player (Digital Accessible Information System) is not a computer-based system, but a device in
itself. It is a device that reads out audiobooks or computerised texts and allows users to navigate through the text.
There are devices similar to the DAISY player which are also developed to support dyslexics, but they will not be
further described in this thesis. Since ICT is developing at a rapid pace, more ICT resources are becoming available
to dyslexics. The DAISY player is among the devices that are used less and less in the Netherlands (Tweede Kamer
der Staten-Generaal, 2012), while ICT products that can be used on a computer or tablet are taking the upper hand.

These tools were all designed to facilitate dyslexics in a practical way. The TOA in its current form, however, does not
offer any options to facilitate dyslexics, except for extra test time. In the next chapter, a more theoretical approach will
be taken, comparing different theories and reflecting on experiments that tested various typographical measures. The
most important results from this literature review will be implemented in this thesis’ experiment, in which textual
features will be altered in the TOA, testing whether dyslexic users of the TOA do also benefit from these changes.

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3 Theory

3.1 Historical account of reading theories
This paragraph offers a historical account of reading theories, or more specific, theoretical approaches towards
reading processes. This is an essential basis that provides information on the overall picture of reading, before the
more specific theories, narrowed down to dyslexia, will be discussed.

At the time when research into developmental dyslexia was only emerging, a psychologist named Chall wrote a book
about the different approaches towards reading. It was called Learning to read: The great debate (1967) and it explains
concepts such as the bottom-up or the top-down approach with regard to dyslexia. This book was published years
after her co-authored article on the ‘Dale-Chall readability formula’ (Dale & Chall, 1948), in which a mathematical
formula to measure readability was introduced, expressed in a number representing readers’ comprehension difficulty.
This formula is based on a ratio between both difficult words and the number of words, and the number of words
divided by the number of sentences. However, although being extensively used for decades, the formula eventually
did not make it in the world of ever-changing and -developing linguistics. Perhaps because of the almost indefinability
of terms such as ‘difficult words’, but more likely because of the increasing knowledge and awareness concerning the
reading problem called dyslexia, which was more and more being perceived as a cause for reading difficulties. A
model describing these difficulties, but not linking them to dyslexia, grew to be outdated. Furthermore, it became clear
that dyslexia is not just a plain disorder or deficiency and that formulating its causes and development is more
complicated than a simple formula. Hence, more and more theories have been developed and tested over time.

Chall’s The great debate (1967) offers an overview of research conducted between 1910 and 1965. In these years, the
main distinction in reading theories was between bottom-up and top-down approaches. In bottom-up theories, reading
development starts from primitive processing (one letter, two letters) to advanced processing (word, sentence, text).
This information processing model focuses on training phonological awareness, letter recognition and synthesis. A
typical hypothesis coming from bottom-up thinking is failing short-term memory: While reading, letters need to be
remembered and stored in the short-term memory, at least until the word is finished. In this case the short-term
memory functions as a buffer memory in which information is being retained, while semantic information is being
retrieved from the long-term memory. Top-down theories focus on meaning rather than content. Readers are
constantly predicting what is to come, based on context and understanding. Chall’s conclusion is that children
beginning to read gain more benefit from bottom-up teaching methods, focused on decoding skills, rather than top-
down methods, focused on the reader and making them aware of how they process text and how they should contrast
text with their world knowledge. Subsequently, an interactive model of reading arose, taking into account both
approaches. This resulted in findings such as the word superiority effect (a letter in a well-known word is recognised
more easily than a letter in a pseudo-word), the word frequency effect (frequent words are better recognised than less
frequent words), context superiority (words are more easily recognised within a context), and the neighbour frequency
effect (pseudo-words with great similarity to real words take longer to be recognised than pseudo-words without so-
called neighbours). This last finding, however, is remarkable: Ziegler and Goswami (2005) found that words, real
words, were more easily recognised when they had many neighbours because phonological similarity, or rhyme,
contributes to phonological awareness.

A reaction to this information processing model is the dual route model (Van den Broeck, 1993). This model
assumes information in the mental lexicon can be activated in several ways: through pronunciation, word meaning,

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word image, etc. The two routes described in the model are the direct or lexical route, and the indirect of phonological
route.

Another reaction to the information processing model is the connectionist model (Van den Broeck, 1993),
which assumes the memory is a network of fragments instead of a lexicon with words. In this view, reading
development is the building of a network of co-occurring fragments in which frequent words are retrieved more easily
than less frequent words. Reading consists of sounds and of horizontal and vertical lines creating images, and
together these two elements add up to a grapheme-phoneme correspondence, enabling phonological decoding.

These are just a few of the many general theories about reading. In the following chapters of this thesis, more recent
theories regarding developmental dyslexia will be discussed.

3.2 Theoretical perspectives
The main focus of this section of the thesis will be the evaluation of several theoretical perspectives on dyslexia.
These theories sometimes overlap and sometimes contradict each other, but by all means they construct a framework.
A broad framework, supported by very different views, all contributing in some way to the shaping and making of ‘the
dyslexia theory’ – perhaps someday a valid, accurate theory embodying all aspects that make dyslexia such a
complex deficiency.

This evaluation of theories is divided into two main branches: On the one hand, theories attempting to explain
dyslexia, to break down its causes and label its effects; on the other hand, theories describing methods aiming to
facilitate dyslexics. Not included in this thesis are the remedial theories; the branch that focuses on training dyslexics
in linguistic subskills, such as auditory perception and phonological discrimination. Coping with dyslexia consists of two
pillars: remediating and facilitating. The focus in this thesis will be on facilitating as a way of coping with dyslexia.

These facilitating theories are mainly focused on typographical alterations, in-text adjustments to facilitate the dyslexic
as much as possible. The other theories may be categorised by type of theory: The main emphasis is on neurological
theories, including the phonological deficit hypothesis, the rapid auditory processing theory, the visual theory and the
cerebellar deficit theory. Taken together, these four theories form the foundation of the magnocellular theory, which is
currently a leading theory in dyslexia research. Besides these neurological viewpoints, other theories such as cognitive
theories, evolutionary theories, genetics and the noise-exclusion hypothesis are also taken into account. Furthermore,
comorbidity will be considered, as well as dyslexia’s ‘side effects’ such as less-developed motor skills, self-esteem,
creativity and entrepreneurial skills.

3.2.1 Explaining dyslexia

3.2.1.1 Neurological and cognitive theories
In their research into major leading theories of developmental dyslexia, Ramus et al. (2003) describe the
magnocellular theory as a unifying theory of the phonological, rapid auditory processing, visual and cerebellar deficit
hypotheses. Moreover, it is a generalisation of the visual deficit hypothesis, not restricted to visual aspects but also
linked to other modalities. Before digging into the magnocellular theory, the theories which the magnocellular theory is
composed of will be described and discussed in order to obtain a clear view and to provide a comprehensible account
on leading theories in dyslexia. Through these neurological and cognitive theories we will work towards the
magnocellular theory and have a critical look at its claims and evidence.

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Phonological deficit hypothesis The phonological deficit hypothesis postulates that people with dyslexia have a
specific impairment in the representation, storage and retrieval of speech sounds (Ramus et al., 2003). Dyslexics also
have an impaired automatisation of the grapheme-phoneme correspondence because sounds are poorly represented,
stored and retrieved. They perceive phonetic boundaries less sharply than typically developing readers do (Vellutino et
al., 2004). Dyslexics also show a poor performance on phonological awareness tasks, for example tasks that include
consciously segmenting or manipulating sounds (Ramus et al., 2003; Snowling, 1998). They have trouble
discriminating between phonemes and therefore often confuse letters that sound alike, such as s, sh, th, f and v (Stein
& Walsh, 1997). Wolf and Bowers describe the basis of the phonological deficit hypothesis as a deficit in phonological
processes, impeding “the acquisition of word recognition skills, which, in turn, impedes the acquisition of fluent
reading” (1999, p. 415).

Ramus et al. (2003) and Snowling (1998) argue whether dyslexia is a more basic deficit in the access and
retrieval in short-term memory, which explains the low quality of the automatisation of the phonological
representations. Shaywitz et al. (2002) also attribute dyslexia to a dysfunction in the left hemisphere of the brain,
which is mainly responsible for language production and comprehension.

Apart from a deficit in short-term memory, Snowling (1998) states that dyslexics have trouble with long-term
memory learning and retrieval as well, such as learning the days of the week, or the months of the year, multiplication
series or learning a foreign language.

A typical strategy for a dyslexic is to rely on visual information instead of decoding sounds, according to Stanovich
(1988), who describes dyslexia as a phonological-core deficit. On the other hand, there are also dyslexics who rely
heavily on grapheme-phoneme associations instead; pronouncing ‘island’ as ‘izland’ and ‘glove’ as ‘gloave’, the so-
called morphemic or surface dyslexics (Snowling, 1998). These dyslexics particularly have problems with irregular
words and tend to spell out words while reading. They would not be accounted for if dyslexia were a phonological
problem only. Nevertheless, Snowling (1998) explains that most dyslexics are phonological dyslexics, who, for
example, have difficulties recognising pseudo-words. These dyslexics have an actual developmental disorder, whereas
morphemic or surface dyslexics are simply developmentally delayed (Snowling, 1998). As such, both types of dyslexia
are compatible with the phonological deficit hypothesis.

The phonological deficit hypothesis, or phonological theory, accounts well for the symptoms of dyslexia
across the lifespan: Adult readers are often fluent but slow readers and still have trouble with spelling, decoding
pseudo-words, rapid naming, verbal short-term memory tasks, and their phonological awareness is poorer compared
to their peers (Snowling, 1998).

Evidence for the phonological deficit hypothesis comes from different fields of study. Snowling (1998) claims
that in terms of genetics, phonological aspects of reading have a greater inheritability than visual aspects.
Furthermore, PET scans showed that for dyslexics, the insula (a brain structure between Broca’s area and Wernicke’s
area) showed reduced activity (Snowling, 1998). The insula is an area that is associated with the intermission of
language and that transitions spoken language input and speech production. When this activity is reduced, as it is with
dyslexics, one can indeed speak of a phonological problem (Snowling, 1998).

More evidence in favour of a phonological deficit is described by Vellutino et al. (2004). Among phonological
deficiencies are problems with word identification, phonological awareness, letter-sound decoding, rapid naming and
verbal memory. Vellutino et al. describe research in which direct instructions and training, designed to facilitate
phonological awareness, seemed to have a positive effect on spelling, word identification and reading ability in general
(2004). As Vellutino et al. state, this “evidence garnered from these more direct tests of the weak phonological coding
theory of reading disability, although inconclusive, is highly suggestive” (2004, p. 13).

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But what distinguishes the dyslexic reader from other poor readers? In his phonological-core variable-difference
model, Stanovich describes dyslexia as a discrepancy between reading and intelligence (1988). In general, pure
dyslexics have a normal or higher IQ compared to the ‘garden-variety poor reader’, who have a lower IQ. But, and this
is where the phonological-core variable-difference model comes in, pure dyslexics with a low IQ or garden-variety
readers with a high IQ are not accounted for in existing models: The term ‘variable-difference’ is used to indicate the
contrast between the pure dyslexic and the garden-variety poor reader. Dyslexia, in the light of this model, is “a
domain-specific process” (Stanovich, 1988, p. 601), for it is a deficit that is solely related to reading. When the deficit
is related to IQ, it becomes an intelligence problem, thereby reducing the discrepancy between reading and
intelligence, in which case it is more likely the child is not dyslexic.

Stanovich (1988) describes a causal relationship between phonological skills and reading ability. His
phonological-core variable-difference model is linked to a formula (figure 1) by which reading comprehension can be
calculated (Gough & Tunmer, 1986).

Fig. 1: Reading comprehension as a product of decoding skill and listening comprehension ability (Gough & Tunmer, 1986).

To exemplify this, D and C could be given a score: When decoding skill D equals 4 and listening comprehension
ability C equals 9, reading comprehension R scores 36. But when D scores 6 and C scores 6 as well, R is still 36,
meaning reading comprehension is, although different in composition, equal in both cases. According to Stanovich
(1988), the phonological-core variable-difference model offers an explanation for phonological deficits, but other
deficits as well. It constructs a multidimensional framework that represents pure dyslexics, garden-variety poor readers
and everything in between (Stanovich, 1988). Badian (1994) tested this model by comparing dyslexics, garden-variety
poor readers and good readers, finding that both dyslexics and garden-variety poor readers have phonological
processing deficits, but that these deficits are more extensive in dyslexics. This supports the phonological-core
variable-difference model (Stanovich, 1988).

Ramus et al. (2003) also state that dyslexia does not consist of a single (phonological) deficit, but that it is
rooted in more general sensory, motor or learning processes. Snowling (1998) claims dyslexia is a phonological
disorder. However, she also argues that “the course of reading development followed by a particular dyslexic child will
be determined not only by the severity of their phonological processing problem, but also by their other language
skills” (Snowling, 1998, p. 8).

Clearly, the phonological deficit hypothesis does not meet all researchers’ expectations and requirements for an all-
embracing theory when it comes to dyslexia. A new hypothesis, building on the phonological deficit hypothesis but
also taking into account processes underlying naming speed, was created: the double-deficit hypothesis (Wolf &
Bowers, 1999).

Double-deficit hypothesis The double-deficit hypothesis, as its name suggests, consists of two hypotheses: The
phonological deficit hypothesis, discussed above, and a hypothesis assuming a deficit in processes underlying naming
speed (Wolf & Bowers, 1999). These hypotheses are two separable hypotheses; not necessarily co-occurring, but
when they do – ‘the double-deficit hypothesis’ – they lead to profound reading impairment.

Naming speed tasks provide a “microcosm of reading, a window on how rapid visual-verbal connections –
essential to reading – are made in the developing child’s system” (Wolf & Bowers, 1999, p. 418). Besides, it provides

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information on how children derive orthographic patterns from exposure to print text. Naming speed can be measured
by the rapid automatized naming (RAN) test (figure 2) designed by Denckla (1972, in Wolf & Bowers, 1999). The RAN
is composed of 50 stimuli, letters in this example.

Fig. 2: Rapid automatized naming (RAN) task for letters (Denckla, 1972, in Wolf & Bowers, 1999).

Deficits in naming speed derive from different sources. Wolf and Bowers (1999) mention three: 1) a disruption in
lexical access and retrieval; 2) a slower processing speed of perceptual or motoric processes; and 3) a consistent
deficit in perceptual or motoric processes, affecting the speed of lexical retrieving processes (p. 430).

Evidence for the naming speed deficit hypothesis also comes from different angles. Dyslexics have more difficulties
processing lower-level visual information than typically developing readers. Besides, in a series of stimuli, for instance
in a RAN task, dyslexics are also having trouble determining whether a stimulus differs from the previous stimulus
(Wolf & Bowers, 1999).

Further proof is found at the motoric level: In a finger-tapping experiment in which children had to tap along
with a simple rhythm provided by a metronome, Wolff (1993, in Wolf & Bowers, 1999) found that dyslexics were
having more trouble tapping asynchronously, compared to normal controls.

In neurophysiological findings, significant differences are found in the lateral geniculate nuclei and the medial
geniculate nuclei in dyslexics’ brains (Livingstone, Rosen, Drislane, & Galaburda, 1991; Wolf & Bowers, 1999). These
areas are known as magnocellular systems, which will be further explained when the magnocellular theory is
explained and discussed.

In summary, Wolf and Bowers state that naming speed tasks are “one of the two best predictors of reading
achievement (along with phonemic awareness tasks)” (1999, p. 430). Before turning to the criticisms and
counterevidence of the double-deficit hypothesis, a schematic overview of the double-deficit hypothesis and its
components is provided in table 1.

hypothesis characteristics examples

Phonological - deficit in phonological decoding The dyslexic has trouble applying grapheme-phoneme

deficit hypothesis - naming speed intact correspondence in a context-free situation (decoding

(pseudo-)words).

Naming speed - deficit in naming speed The dyslexic has trouble identifying words, in particular

deficit hypothesis - phonological decoding intact when rapidly presented in a task.

Double-deficit - deficit in phonological decoding The dyslexic has substantial reading impairments. The

hypothesis - deficit in naming speed dyslexic has trouble decoding (pseudo-)words, as well as

identifying words in a rapid automatised task.

Table 1: Overview of the double-deficit hypothesis and its components.

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Weighing the evidence on the double-deficit hypothesis, Vellutino et al. (2004) doubt Wolf and Bowers’ argumentation
on the lack of a precise timing mechanism in dyslexics (1999). This precise timing mechanism “lacks the type of
specification that would lend it psychological reality and allow it to be evaluated experimentally as a valid hypothetical
construct” (Vellutino et al., 2004, p. 14). In other words, the double-deficit hypothesis is not testable and therefore
invalid.

In addition, more recent views on the double-deficit hypothesis have classified reading fluency as non-
phonological, thereby further invalidating the hypothesis (Vellutino et al., 2004). Other arguments against the double-
deficit hypothesis include implications like motivational factors that may differ between individual dyslexics (Vellutino et
al., 2004). On the other hand, these factors are present in almost every hypothesis.

Most importantly, Vellutino et al. (2004) argue that the two factors, i.e. phonological decoding and naming speed, tend
to correlate. Hence, readers with both deficits have substantially lower phonological awareness scores in comparison
to the readers with a single deficit. However, this effect is mainly due to phonological skills, instead of being a sum of
both phonological deficits and naming speed difficulties. This would plead against the double-deficit hypothesis.

Another theory considers the phonological deficit is secondary to a more basic, auditory deficit (Ramus et al., 2003):
the rapid auditory processing hypothesis.

Rapid auditory processing hypothesis The deficit that makes it so hard for dyslexics to read, “lies in the perception
of short or rapidly varying sounds” (Tallal, 1980). Results from a temporal order judgement task show that dyslexics
perform worse than normal controls (Tallal, 1980). In a temporal order judgement task, two tones are rapidly
presented in succession, and the participants need to determine whether the tones were the same or different
(McAnally, Castles, & Stuart, 2000). The fact that dyslexics have more trouble doing so, shows that their categorical
perception of contrasts is poor compared to normal controls (Ramus et al., 2003).
McAnally et al. found that children with reading disabilities benefit from longer intervals between stimuli in order to
correctly distinguish between two sounds (2000). These results seem to suggest that they need space, quiet intervals,
between stimuli or input; just like they benefit from spacing in written text (Martelli, Di Filippo, Spinelli, & Zoccolotti,
2009; Zorzi et al., 2012). Dyslexics are having more trouble distinguishing between slight changes in amplitude or
frequency of acoustic sounds (McAnally et al., 2000; Stein & Walsh, 1997). On top of that, they have difficulties
detecting “phase differences between the ears” (Stein & Walsh, 1997). Dyslexics also show a delayed response to
frequency change (Watkins, Baldeweg, Richardson & Gruzelier, 1995, in McAnally et al., 2000) and to speech stimuli
(McAnally et al., 2000). In anatomy, the left medial geniculate nucleus, also known as the auditory thalamus, contains
more small cells for dyslexics than for typically developing readers (Galaburda, Rosen, & Menard, 1994, in McAnally
et al., 2000).

McAnally et al. state that “auditory processing deficits are proposed to have caused impaired speech perception:
There is evidence that dyslexics categorize speech stimuli less well than normal readers” (2000, p. 148). These
deficits in speech perception may be the reason dyslexics are having difficulties processing speech and, moreover,
manipulating speech sounds. In other words, their phonemic awareness is poorer than in normal controls (McAnally et
al., 2000).

According to the rapid auditory processing hypothesis, a low-level auditory deficit causes the phonological analysis
problems dyslexics have (Stein & Walsh, 1997; Tallal, 1980). Reed (1989) tried to replicate Tallal’s findings (1980), but
where Tallal tested non-human sounds only, Reed found that dyslexics particularly had trouble with stop consonants

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and tones in human speech, while there was no difference in steady state vowels (i.e. neutral, isolated vowels) for
dyslexics and normal controls.

Vellutino et al. (2004), giving an overview of several deficits found among dyslexics, state that in dyslexics, (low-level)
auditory deficits indeed do exist. However, they do not explain the problems regarding word recognition that these
dyslexics also have. They reject the rapid auditory processing hypothesis because it does not account for all problems
dyslexics have. Moreover, most of the experiments on which these results are based, consisted of sound stimuli that
were of a non-human nature (i.e. no speech stimuli). Therefore, it should not be automatically presumed that these
results can be generalised to speech sounds.

Visual deficit hypothesis The visual deficit hypothesis gathered many of its followers in the previous century.
However, at the turn of the century, many of these supporters had left again. Recently there has been a renewed
interest into the possibility of a visual deficit impairing reading ability. But, this time, the focus shifted from low-level
deficits to a more specific, magnocellular deficit. This will be discussed in a later paragraph. First, the visual theory
and its assumptions are discussed. The visual theory does not necessarily exclude a phonological deficit, but
describes another deficit contributing to the phonological problems dyslexics already have (Ramus et al., 2003).
Ramus et al. (2003) describe one of dyslexics’ visual deficits as having difficulties with processing words on a page of
text. Described possible causes are unstable binocular fixations or poor vergence (Ramus et al., 2003), one of the
effects is called ‘crowding’. Crowding is a perceptual deficit that accounts for sixty percent of dyslexics’ slow reading in
Italian, a language with a transparent orthography (Martelli et al., 2009). For more opaque languages, such as English,
results may differ. Martelli et al. (2009) attribute the effect of crowding to a damaged accessibility to the lexicon.
Crowding will be discussed in more detail in paragraph 3.2.2.3. Stein and Walsh suggest that dyslexics’ confusion with
b and d, for example, is also an effect of crowding: Dyslexics confuse these letters because of a disruption in the
posterior parietal cortex of the brain (1997). A monocular occlusion, or an eye patch, may relieve these problems
partially (Stein & Walsh, 1997).

Getman (1985, in Vellutino et al., 2004) suggests that an oculomotor deficit (a deficit in the oculomotor nerve) causes
visual tracking problems. However, evidence for this case has not been found for non-verbal stimuli (Vellutino et al.,
2004), implying that dyslexia is more than just a low-level deficit. Hulme (1988, in Vellutino et al., 2004) states that
“the trace persistence theory of reading disability predicts that dyslexics should be impaired only when they are
reading connected text and not when they encounter printed words one at a time under foveal vision conditions” (p.
9). However, poor readers do in fact encounter problems when they read printed words in a non-contextual setting
(Vellutino et al., 2004). On the other hand, Vellutino et al. state that “there is no evidence that dyslexics experience
visual acuity- and visual masking problems under normal reading conditions” (2004, p. 9). All these results do not
indicate a sole, low-level visual deficit. McAnally et al. (2000) argue that dyslexia might be caused by a more general
sensory processing deficit.

There is a substantial overlap between many aspects discussed in visual theories and in the magnocellular theory.
These aspects will be discussed in a later paragraph. Before turning to the magnocellular theory, the last component
of this theory will be examined: the cerebellar deficit hypothesis.

Cerebellar deficit hypothesis In an elaborate study of direct and indirect indicators of dyslexia, Nicolson, Fawcett
and Dean (2001) found that 80% of all dyslexics have abnormalities in the cerebellum. These results were obtained by
testing a group of ‘pure’ dyslexics – i.e. dyslexics with an IQ over 90 and no other problems such as ADHD – and a
group of controls in two kinds of experiments. First, they carried out an indirect experiment, containing three tests: a

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balance test including a secondary task, a phonemic segmentation test and a naming speed test. Nicolson et al.
(2001) found that these dyslexic children’s automatisation skills were indeed not as good as the normal controls’ skills
and that this was probably due to a cerebellar deficit, affecting motor skills as well. To verify this, they conducted a
second experiment of a more direct nature: The dyslexics underwent a PET scan. The results from the PET scans
showed that dyslexics had significantly less activity going on in the cerebellum during a trial and error sequence task,
compared to normal controls (Nicolson et al., 2001). It has been generally accepted that deficits in the cerebellum do
indeed affect motor skills, such as a less fluent way of talking and walking for infants and a slower rate of language
acquisition.

In a critical note, Ramus et al. (2003) state that the cerebellar deficit hypothesis is not a complete, all-
embracing theory to fully explain dyslexia. On the contrary, the theory may explain some of dyslexics’ problems, but
does not account for all problems. On the other hand, not all dyslexics do necessarily have a cerebellar deficit. Stein
and Walsh (1997) state that generally, dyslexics’ motor skills are not as good as compared to normal controls. In fact,
dyslexics are “notoriously clumsy and uncoordinated, their writing is appalling, their balance is poor, and they show
other ‘soft’ cerebellar signs, such as reach and gaze overshoot, and muscle hypotonia” (Stein & Walsh, 1997).
However, Ramus et al. suggest that only dyslexics with an additional attention deficit show a motor dysfunction (2003).

Magnocellular theory In their article about the cerebellar deficit hypothesis, Nicolson et al. (2001) describe how the
cerebellar theory offers an explanation for the symptoms of dyslexia. They also state that the phonological and
magnocellular theories fail to account for all deficits and difficulties associated with dyslexia. The cerebellar deficit
hypothesis is an alternative way of explaining the magnocellular deviations, encountered on a biological level, by
attributing the problems to a cerebellar deficit (Nicolson et al., 2001).

On the other hand, Ramus et al. (2003) perceive the magnocellular theory as “a unifying theory that attempts
to integrate all the findings mentioned above” – i.e. the phonological deficit hypothesis, the double-deficit hypothesis,
the rapid auditory processing hypothesis, the visual deficit hypothesis and the cerebellar hypothesis (Ramus et al.,
2003, p. 843). To get a better understanding of these views, the magnocellular system itself needs some explanation.

The magnocellular system, together with the parvocellular and the notably smaller koniocellular system, are layers that
the visual system is composed of. The layers start behind the retina and lead all the way up to the lateral geniculate
nucleus, on which visual input is projected. The magnocellular layer consists of large neurons (‘magno-’ meaning
‘large’), responsible for perceiving contours and movement, but also depth and brightness. Its functions have earned
the system the nickname of the ‘where’-system. The parvocellular layer consists of smaller neurons (‘parvo-’ meaning
‘small’) and is responsible for perceiving finer details and colours, and relaying input from the red and green cones.
The koniocellular system relays input from short-wavelength cones, the blue cones. The magnocellular system is also
called ‘the transient system’ (Skoyles & Skottun, 2004; Vellutino et al., 2004).

The magnocellular theory assumes that dyslexics have a deficit in the magnocellular system, causing dyslexia
(Livingstone et al., 1991; Skottun, 1998; Stein, 2001; Stein & Walsh, 1997; Vellutino et al., 2004). The magnocellular
system is responsible for the tracking of eye movements while reading, for binocular control, as well as maintaining
focus during saccades; the consecutive movements of the eye. In case of a deficit, the magnocellular layer becomes
less sensitive and as a result, dyslexics have a reduced motion sensitivity, causing the letters to move around, merge
into each other and blur (Stein, 2001; Stein & Walsh, 1997). Saccade control is affected as well: In individuals with a
normally functioning magnocellular system, saccades are fluently connected as in a high-frame rate film. When the
magnocellular system is less sensitive, as it is in dyslexics, the images do not fade into each other as fluently as in
typically developing readers, creating the effect of an old, silent film. When the saccades are no longer controlled, the

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process of decoding is disrupted. This causes crowding and hence, letter- and word recognition is disrupted (Stein &
Walsh, 1997).

Researchers used to think the parvocellular system was suppressed by the magnocellular system at the time of each
saccade (Skottun, 1998). However, experiments show that the confusion of letters only happens between directly
neighbouring letters, not between letters at a saccade’s distance (Stein, 2001), and on top of that, evidence has been
provided that the magnocellular system does in fact not inhibit the parvocellular system during saccades (Burr,
Morrone and Ross, 1994, in Stein, 2001; Skottun, 1998). The first interpretation of the magnocellular theory,
considering the magnocelullar system as a suppressor of the parvocellular system, turned out to be incorrect.
Therefore, Stein and Walsh (1997) altered the hypothesis: The magnocellular theory purports that in dyslexics,
magnocellular sensitivity is reduced. This is not only restricted to the visual system, but also to auditory, tactile and
cerebellar modalities (Ramus et al., 2003).

In a normal-functioning magnocellular system, magnocells are gatherers of light from a large area. Typically
developing readers therefore have a fast and good vision. When the sensitivity of the system is reduced, as it is in
dyslexics, vision is not as fast and good. However, this also makes dyslexics more sensitive to the finer details and to
colours, induced by the parvocellular system (Stein, 2001).

Overall, the magnocellular theory assumes that dyslexics have a poor motion sensitivity, which embodies the
ability to determine the correct order of letters in a word (Stein, 2001). They also have a visual perceptual instability,
meaning that the computation of perception is disrupted. Eyes are never stationary; they move constantly, even while
asleep. The magnocellular system does not only control these movements, but also ‘glues’ them together by
transmitting magnocellular signals (Stein, 2001), making the world seem quite stationary for normal-sighted individuals.
Another common feature of dyslexics, according to the magnocellular theory, is unsteady binocular fixation: The two
eyes seem to lack a proper kind of communication, causing the eyes to cross and recross again. This is accompanied
by a lack of strong right- or left handedness, caused by a failure in fixation of hemispheric specialisation (Stein, 2001).
As a result, dyslexic children with unsteady binocular fixation tend to make more visual errors when letter size is
decreased (Cornelissen, Richardson, Mason, Fowler & Stein, 1995) and when letters are crowded close together
(Atkinson, 1991, in Stein, 2001). A commonly used treatment for this specific problem, is monocular occlusion, for
example, covering one eye with an eye patch (Stein, 2001; Stein & Walsh, 1997).

One of the earliest tests to measure magnocellular activity, is the Ternustest (Ternus, 1926). In this test, three
horizontally aligned squares are shortly shown to the participant. Subsequently, a similar image is shown in which it
seems like the three squares have been slightly shifted to the right. This optical illusion is experienced differently
according to the interval between the stimuli: When the interval is shorter than 50 milliseconds, the three squares
seem to have shifted as a group, while an interval longer than 50 milliseconds makes it seem as if only one of the
squares has shifted. This motion is perceived differently by dyslexics; they have more difficulties noting the group of
squares’ optical illusion than typically developing readers (Slaghuis, Twell and Kingston, 1996, in Wildhagen, 2011).

A more recent test to measure movement detection is the random dot kinematogram test or RDK (Newsome
& Paré, 1988). In this test, randomly, constantly moving dots are shown on a screen. The participant has to point out
a coherent cloud of movement in the constantly moving dots (figure 3). RDKs, probing the whole magnocellular
system, have shown that dyslexics have more difficulties detecting motion (Newsome & Paré, 1988; Stein, 2001).

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 21

Fig. 3: Random Dot Kinematogram (Newsome & Paré, 1988).

More evidence for a magnocellular deficit comes from post mortem examinations. In dyslexics, neurones in the
magnocellular layers were 30% smaller than in control brains, as well as the corresponding receptive fields
(Livingstone et al., 1991; Stein, 2001). Galaburda, Lemay and Kemper (1978, in Stein, 2001) found that the normal
asymmetry of the planum temporale, caused by right- or left handedness, is missing in dyslexics. This, again,
indicates a lack of fixation of hemispheric specialisation (Stein, 2001).

The posterior parietal cortex, in which ‘directed auditory attention’ is organised, is also connected to dyslexia:
A lesion in this particular area causes so-called ‘cocktail party’ problems, or in other words, difficulties focusing
auditory attention on one source, filtering out all other sources (Stein & Walsh, 1997).

A deficit in the magnocellular system also causes reduced contrast sensitivity (Lovegrove, Martin, Blackwood,
& Badcock, 1980, in Stein & Walsh, 1997; Skottun, 1998). However, Stein and Walsh argue that these observations
have only been made at low luminance levels, not at normal or high luminance levels (1997).

The magnocellular theory of dyslexia is a strong theory that accounts for many aspects of dyslexics’ problems in
reading ability. But, as with every theory, critical remarks have been made by more than one researcher. Ramus et al.
(2003) describe how attempts to replicate the auditory deficits caused by a magnocellular deficit, have failed. They
also state that “the magnocellular theory suffers mainly from its inability to explain the absence of sensory and motor
disorders in a significant proportion of dyslexics” (Ramus et al., 2003, p. 844).

Another substantial piece of counterevidence comes from Skoyles and Skottun (2004). In their experiment,
they tested not only dyslexics for a magnocellular deficit, but also typically developing readers. They found a
magnocellular deficit in relatively more typically developing readers than in dyslexics (Skoyles & Skottun, 2004),
suggesting a paradoxical overdiagnosis. On the other hand, Amitay, Ben-Yehudah, Banai and Ahissar’s results (2002)
indicate an underdiagnosis: Only 20% of the dyslexics they examined had a magnocellular deficit, but were impaired
on other perceptual tasks.

Noise-exclusion hypothesis Finally, Sperling, Lu, Manis and Seidenberg (2006) state that there is no such thing as a
magnocellular deficit in dyslexics. Rather, it is a deficit in noise-exclusion that makes it hard for dyslexics to read. They
describe this noise-exclusion hypothesis as a theory that predicts that dyslexics “will show performance deficits in both
magnocellular and parvocellular types of tasks in the presence of high levels of external noise, and in neither type of
task at lower levels of external noise” (Sperling et al., 2006, p. 1047). The noise, in this case, refers to distracting
features around or within texts, such as background colour. Besides excluding external noise, Sperling et al. also
suggest that dyslexics may have a deficit in signal enhancement, resulting in problems with “maintaining signal
integrity during processing” (2006, p. 1047). Taken together, these two mechanisms affect how the dyslexic’s attention
may improve his perception. Sperling et al. tested these claims in two experiments, including a word attack task, a
word identification task and an orthographic choice test (2006). Results from these experiments included a higher
contrast threshold for poor readers in a high-noise condition and to both poorer phonological decoding skills and

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 22

orthographic skills in the high-noise condition. This leads Sperling et al. to believe that the presence or absence of
noise is related to general reading ability and not to a specific reading skill (2006).

Sperling et al. finally state that their results construct a consistent picture (2006): Poor readers had higher
contrast thresholds in high-noise conditions than normal readers. When the amount of noise was reduced, there were
no differences between poor and normal readers.

Researchers are still disputing the question whether a magnocellular deficit does indeed cause dyslexia or not. The
magnocellular theory will remain a subject of interest, but the emergence of new theories, such as the noise-exclusion
hypothesis (Sperling et al., 2006) makes the magnocellular theory waver.

3.2.1.2 Comorbidity

In an extensive experiment, Menghini et al. (2010) researched what other underlying neurocognitive causes occur in
children with dyslexia. They used several kinds of tasks to test phonological processing, visual processing, attention,
learning, and executive functions. Their research provides an overview of comorbidity in children with dyslexia,

(table 2).

comorbidity 76.6% no comorbidity 21.5%

- phonological deficit and executive deficits 16.6% - phonological deficit 18.3%
- attention deficit 1.6%
- phonological deficit, visual-spatial perception deficits, 13.3% - motion perception deficit 1.6%

attention- and executive deficits

- phonological deficit, attention- and perception deficits 8.3%

- phonological deficit, attention- and executive deficits 8.3%

- other combinations 30%

Table 2: Comorbidity in children with dyslexia (Menghini et al., 2010).

The results show that in many cases of children with dyslexia, other cognitive deficits are found as well (Menghini et
al., 2010), mainly executive deficits which are often linked to ADHD (Attention Deficit and Hyperactivity Disorder).
Vellutino et al. (2004) vaguely support this claim by stating that 30-70% of all dyslexics also have ADHD. They
mention this rather broad range because the exact number is dependent on how ADHD is defined (Vellutino et al.,
2004). Stein and Walsh (1997) mention that attention problems in dyslexics cause crowding, for the reader will be
distracted by neighbouring words.

Pennington, Groisser and Welsh (1993) tested what symptoms were stronger in comorbid children with both dyslexia
and ADHD. They hypothesised that ADHD symptoms are secondary to symptoms associated with dyslexia. To
measure this, they tested three groups of children: 1) children with dyslexia, 2) children with ADHD, and 3) children
with both dyslexia and ADHD. Two cognitive domains were tested: phonological processes, associated with dyslexia,
and executive functions, associated with ADHD. They found that both the dyslexics and the comorbid group (with both
dyslexia and ADHD) were impaired on the phonological processing task, but scored normally on the executive
functioning task (Pennington et al., 1993). Vice versa, the ADHD group scored normally on phonological processes,
but had low scores on executive functioning. Pennington et al. (1993) stated that these results indicated a double
dissociation between dyslexics and children with ADHD. On top of that, ADHD symptoms were found to be secondary
to dyslexia symptoms, proving their hypothesis to be true.

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 23

3.2.1.3 Evolutionary theory
A more philosophical approach is taken by Dalby (1986), who focuses on asking ‘why’ questions instead of ‘how’
questions. An example: The previously discussed theories were about issues like ‘how does a dyslexic child learn to
read’ or ‘how does the magnocellular system work’. Dalby changes these questions: ‘Why does a dyslexic child learn
to read’ and ‘Why does the magnocellular system work’. He approaches dyslexia as a problem that man has only
‘recently’ encountered; only since we began to develop a way to write down our speech and, moreover, since written
text became available to the masses through the movable printing press in the 15th century. Dalby states that “[t]he
human ability to speak stands in sharp contrast to our reading facility” (1986, p. 228).

Taking the declining illiteracy rates into account, the majority of the world citizens has only been reading since about
1950. Dalby philosophises that, in terms of evolution, this time has been too short for man to adapt (1986). Reading
skills have only been needed for a short time, and therefore our body, our physique, has not yet adapted to these
newly required skills (Dalby, 1986; Stein, 2001). However, if this is true, this philosophy does not account for the
majority of people who experience no difficulties in reading whatsoever. Besides, written word has been around for
much longer than the 1950s, Egyptian hieroglyphs and Chinese characters being early examples.

3.2.1.4 Genetics
Mankind has not been reading long enough, in terms of evolution, to be fully adapted to these specialised skills. This
idea is shared by McGrath, Smith and Pennington (2006). They state that “reading is a recent cultural invention for
which specific genes are unlikely to exist” (p. 337).

Contrary to these claims, researchers have found several chromosomes that might be responsible for
dyslexia. This genetic approach considers dyslexia as a genetic deficit, a heritable reading disability, marked in several
genes: Chromosome 6 has been found to be involved in dyslexia (Shaywitz & Shaywitz, 2005; Stein, 2001; Stein &
Walsh, 1997; Vellutino et al., 2004), as well as chromosomes 2, 3 and 15 (Fagerheim et al., 1999; Shaywitz &
Shaywitz, 2005). It has been proved that both orthographical and phonological ability are regulated on chromosome 6
and that they may co-occur on this chromosome, but may occur separately as well. This finding suggests that there
are at least three genes involved: one for orthographical ability, one for phonological ability and one for a combination
of the two (Vellutino et al., 2004). McGrath et al. (2006) propose four candidate genes, three of which are certainly
involved in dyslexia (ROBO1, DCDC2, KIAA0319) and one of them is very likely to be involved (DYX1C1). Powers et
al. (2013) found that some variants of a gene regulator called READ1, located on the DCDC2 gene, are associated
with reading difficulties, while other variants are responsible for verbal language. They also stated that these particular
gene regulators interact with the KIAA0319 gene (Powers et al., 2013). Hawke, Olson, Willcut, Wadsworth and
DeFries (2009) claim that the x-chromosome is the chromosome on which dyslexia is located.

Many studies confirm that family history is one of the most important risk factors for dyslexia (Hawke et al., 2009;
Scarborough, 1990; Snowling, 1998; Stein, 2001; Vellutino et al., 2004): 23-65% of the children whose parents have
dyslexia have reading difficulties as well (Scarborough, 1990), and the other way round: 25-60% of dyslexic children’s
parents also display reading difficulties (Vellutino et al., 2004). More proof for a genetic basis of dyslexia comes from
twin studies: Concordance rates for monozygotic twins are above 80% (Vellutino et al., 2004). Stein explains that the
heritability, i.e. “the amount of variance in reading ability that can be explained by inheritance rather than environment”
(p. 28), is 60% (2001). Other studies, reviewed by Vellutino et al. (2004), position this number between 50% and 60%.
The probability for a boy to become dyslexic when his father is dyslexic, is 50%. When his mother is dyslexic, the
probability is 40% (Snowling, 1998). These probabilities are slightly lower for girls.

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 24

The difference in prevalence between boys and girls is very likely to be of a genetic nature (Hawke et al.,
2009). Possible causes Hawke et al. describe for gender differences are immunological factors, differences in brain
functioning, sexual imprinting and perinatal complications, i.e. complications around childbirth (2009). Females may
also be less susceptible for environmental factors such as socio-economic status or education. A possible explanation
for the fact that the prevalence of dyslexia is greater for males, is that the variance for reading performance is greater
for males (Hawke et al., 2009).

If dyslexia is a genetic problem, it has to be a universal problem, present in all sorts of people and in all kinds of
languages. However, “the nature and prevalence of dyslexia differs across languages” (Paulesu et al., 2001, p. 2165).
The main cause for differences across languages is the orthography of the language: When a language has a shallow
orthography, Italian for example, it may be classified as relatively easy to read because of a direct grapheme-
phoneme correspondence. A language with a more opaque orthography, such as English, is relatively difficult to read
(Helmuth, 2001; Martelli et al., 2009; Paulesu et al., 2001). Helmuth states that the relative number of dyslexics in the
United States is twice as high as it is in Italy, probably due to the opacity of the language (2001).

There is still much to be discovered when it comes to genetics. McGrath et al. state that “genetics is still in its infancy
with respect to understanding the complexity of gene regulatory regions” (2006, p. 338). Dyslexia could possibly be
identified in an earlier stage as the field of genetics continues to develop.

3.2.1.5 Side effects
Dyslexia is generally classified as a reading and spelling deficit, making reading and writing considerably harder for
those affected. However, recent developments were made in research into the other side of dyslexia; the positive side
of dyslexia. This field of (popular) science focuses on the good qualities dyslexics have and the neurocognitive
advantages they possess. In February 2012, an article appeared in the New York Times called The upside of dyslexia
(Murphy Paul). In this article, Murphy Paul describes dyslexia not just as a deficit, but also as a gift, moreover, as a
talent (2012). She states that dyslexics are not always the ones with learning problems, but are in some cases
superior learners. One of their talents is taking in a scene as a whole, having an overview of a situation; possibly
caused by a more efficient parvocellular system (Murphy Paul, 2012; Stein, 2001) which provides a sharper peripheral
vision. Dyslexics show a heightened development of the parvocellular system, making them more artistic, creative,
holistic and entrepreneurial (Stein, 2001). Glaudé (1988, in Billiaert, 2003) suggests that an overproduction of
testosterone disturbs the development of the left hemisphere, resulting in an overdeveloped right hemisphere. As a
result of this, dyslexics are more creative, but also more often left-handed. On top of that, he states that the
development of the thymus is inhibited, which results in a weaker immune system and a greater risk of allergies
(Glaudé, 1988, in Billiaert, 2003). Popular scientific evidence for the entrepreneurial talents of dyslexics is found in
individuals such as Richard Branson, Steve Jobs, Winston Churchill, but also Hans Christian Andersen, Leonardo Da
Vinci, Thomas Edison and Albert Einstein; all of whom are said to be or have been dyslexic (Gonzalez, 2011; Logan,
2009; Stein, 2001).

Logan conducted a study into the incidence of dyslexia in entrepreneurs and corporate managers (2009).
She found that dyslexia was more frequent among entrepreneurs than among corporate managers. Another finding
was that dyslexic entrepreneurs have significantly more staff than non-dyslexic entrepreneurs. Compared to non-
dyslexic entrepreneurs, they more often own more than one business. However, they do run companies for a
significantly shorter time. On a critical note, these results were acquired using a questionnaire, of which only the
statistically significant findings have been discussed here. Logan mentions many other non-significant ‘findings’ and

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uses several different significance levels (α ranging from .01 till .1). The results obtained in this study should therefore
be interpreted “with caution” (Logan, 2009, p. 344).

Not all side effects of dyslexia are positive, though. The process of diagnosing can be long and tiresome, not to
mention the reading difficulties that a dyslexic has to live with. Stein describes how dyslexics can end up in a
downward spiral, bringing along feelings of misery, frustration, depression, even aggression and delinquency (2001).
In a review article, Burden concludes that dyslexics have a low academic self-concept, that they are vulnerable to
depression and that dyslexia has a negative effect on children’s self-esteem (2008). An important factor in their
feelings is the moment of diagnosis and how it is explained to them (Burden, 2008).

Mortimore and Crozier investigated in what way students in higher education experience difficulties caused
by dyslexia (2006). They asked students about their use of numerous support systems, divided into seven categories,
using a questionnaire. These categories were exam assessment, tutorial support, group activities, IT support,
coursework support, lecture support and other kinds of support. They distinguished between three optional responses:
‘have used’, ‘would like to use’ and ‘no need to use’. Most dyslexics’ needs, often unmet, were related to coursework
and lecture support, such as organising coursework, expressing ideas in writing and taking notes. IT support scored
very low in the ‘no need to use’-category, meaning that dyslexics rate it as important and either use it or would like to
use it. The extra time that is often given to dyslexics during exams is also appreciated: 62% have used this kind of
support and 18% have not, but would like to use it. Only 20% of the dyslexics claim that they feel no need to use
extra time (Mortimer & Crozier, 2006).

Beside this inventory of needs among dyslexics, Mortimer and Crozier also asked students about their self-
esteem and self-confidence (2006). Several students felt anxious about assessments, or inferior because of their
reading difficulties. Others reported frustration because of the delay “to get it sorted” and having dyslexia recognised
by the university (Mortimer & Crozier, 2006, p. 248) or because of the constant need to explain they are entitled to
extra time on exams.

Dyslexics need additional support systems in education, it is up to educational institutions to make resources available
(Mortimer & Crozier, 2006). These resources may ease the burden for dyslexics and may alter the negative impact on
their self-esteem and self-confidence. In the next part of this thesis, more facilitating resources will be discussed,
compared and eventually tested.

3.2.2 Facilitating dyslexia / Typographical effects
In contrast to the previously discussed theories, which focused on explaining dyslexia, the theories discussed in this
paragraph are about facilitating dyslexia. Moreover, these theories are about typographical effects, for instance font
type, font size and spacing; but also colours and contrast. The goal of this paragraph is not only to provide a
theoretical account of typographical effects, but also to work towards a practical implementation of these measures.
These will be put to direct use in an experiment comparing different testing conditions within a group of dyslexics,
which will be described in more detail in chapter 4.

One possible explanation for reading comprehension found in literature is the earlier discussed formula by Gough and
Tunmer (figure 1), describing reading comprehension as a product of decoding skill and listening comprehension
ability (1986). Another example is the phonological-core variable-difference model by Stanovich (1988) that expands
Gough and Tunmer’s formula (1986), constructing a framework that represents all readers: dyslexics, garden-variety
poor readers and normal or good readers. These models attempt to explain how people read and what factors affect

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this reading process from within, internally; that is, they describe biological, neurological or cognitive factors affecting
reading ability. The following paragraphs focus on external factors, more specifically, typographical factors.

There are many typographical features described in literature that influence the way dyslexics, but also readers in
general, read. In other words, typographical features play a role in the readability and legibility of a text. Russell-Minda
et al. (2007) define readability as a measure to describe “which font design is the most appealing or comfortable to
the reader” (p. 403). In this definition the term ‘font design’ is one with many interpretations: the height of letters, the
size of letters (or magnification), the space between letters, the presence or absence of serifs; but also more general,
textual features such as contrast, illumination and leading, by which the space between lines of text is meant. There
is, however, a subtle difference between readability and legibility. Readability is generally used to express how
readable a larger body of text is, and not as much single characters, whereas legibility may be interpreted as a
measure for more specific textual features, such as serifs, and their influence on how much effort it takes to read the
text. In this chapter, the interpretations of ‘font design’ will be discussed. In the end, the most apparent, evident
features will be implemented in an experiment.

3.2.2.1 Font type
The term ‘font type’ refers to the collection of typefaces, for example Times New Roman or Arial. One distinct feature
that is regularly used to divide typefaces into two main categories is the presence or absence of serifs. Serifs are best
explained through an example. Figure 4 shows a comparison between Times New Roman and Arial.

The quick brown fox jumps over the lazy dog.

The quick brown fox jumps over the lazy dog.

Fig. 4: Serif and sans serif: typefaces Times New Roman (serif) and Arial (sans serif).

Other examples of typefaces with serifs are Courier and Georgia. Typefaces without serifs are Calibri, Comic Sans
MS, Microsoft Sans Serif and the recently developed Dyslexie (Boer, 2009). Serifs are known to have an effect on
readability (Arditi & Cho, 2005). More specific, they help making letters distinctive. Lockhead and Crist (1980) state
that dyslexics do not particularly have difficulties identifying letters, but distinguishing letters; discriminating between
letters. In this view, a letter in itself is not particularly hard or easy, but the relations between letters determine the
readability of a typeface. This idea has been described by De Vinne more than a century ago:

A letter of modern cut is really not so distinct as the same letter in the old style. The old punch-cutter and the
modern-punch cutter worked to reach different ends. The old cutter put readability first; he would make his types
graceful if he could, but he must first of all make them distinct and readable in a mass. The modern punch-cutter
thinks it his first duty to make every letter of a graceful shape, but his notion of grace is largely mechanical. (1900,
p. 190)

From this we may conclude that letters serve different purposes for different kinds of people. In De Vinne’s example,
dating back to the 1900s, letters are formed in agreement with artistic trends of time. Today, from our perspective,
letters should be simple, not distracting and easy to learn and to read (Lockhead & Crist, 1980). Serifs play an
important role in this. According to Arditi and Cho (2005), who use the terms readability and legibility interchangeably,
serifs have two major impacts on readability and legibility: First, they make the spatial code of letters more complex,
thereby increasing letter discriminability. Second, serifs increase the visibility of strokes, the lines of which letters are
made up, which increases the salience of the strokes. Used in this way, serifs can enhance legibility. On the other

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 27

hand, when used in a wrong way, serifs may also decrease legibility. When they are used mainly ornamental, as
described in De Vinne (1900), they might act as a form of noise (Arditi & Cho, 2005). This was measured in a
staircase method-experiment in which five letters were put in a row and different sizes of serifs were applied to the
letters. Serifs interfered with legibility at the smallest letter size. However, it is unsure whether this is because of serif
size or because of the smaller spacing that comes with smaller serif size. In two other experiments by Arditi and Cho,
serif size did not show any significant effects (2005). In one of these experiments they found a non-significant
tendency that enlarging serifs with 5% was legibility-enhancing. On the contrary, another non-significant tendency
showed that enlarging serifs with 10% was legibility-reducing. However, these results cannot be easily generalised, for
Arditi and Cho only used one single font in their experiment. On top of that, the experiments’ participants were readers
with low vision, not dyslexics.

Similar results were found in Lockhead and Crist (1980) who carried out an experiment in a kindergarten
class. The participants were children who had not learned to read yet. The experiment consisted of a sorting task of
letters written on cards, one card per letter. Some letters had an extra feature on it, a dot or something similar to
make the letter more distinguishable. In this experimental setting, differences between letters like b, d, p and q were
increased, making them more discriminable (figure 5). The modified letters were sorted faster than the original letters.

Fig. 5: Making letters distinctive by adding features (Lockhead & Crist, 1980, p. 486).

In another experiment by Lockhead and Crist (1980), adults showed similar results, leading the authors to conclude
that “the relations among features determine whether stimuli will be perceived as similar or different from one another”
(p. 493). This is in line with results from Bernard, Chaparro, Mills, and Halcomb (2002), who state that serifs are not
always strictly ornamental, but may also have a function, i.e. discriminating individual letters from one another.

In summary, one century after De Vinne’s statement against the ornamental serif (1900), counterevidence against this
case comes from Lockhead and Crist (1980), Arditi and Cho (2005) and Bernard et al. (2002).

But this does not mean that serifs are by definition always helpful and facilitating for readers. Bernard et al. (2002)
hints that serifs might act as a form of noise, especially on computer screens, as described in the noise-exclusion
hypothesis (see paragraph 3.2.1.1). In 2003, Bernard Chaparro, Mills, and Halcomb suggest that “the presumed
greater readability of serif typefaces for print material might be reduced, or even eliminated on a computer because of
the screen’s display characteristics” (2003, p. 824-825). Bernard et al. had already tested this in an experiment
including four fonts in two different point sizes, one year earlier (2002). The fonts with serifs were Times New Roman
and Courier, and the fonts without serifs were Arial and Comic Sans MS. The two point sizes were 12 and 14. The
point size of 14 turned out to be easier to read than the point size of 12. Courier turned out to be less readable than
the other fonts, in contrast to earlier results in which Courier was used as a bold font and showed significant
advantages over Times New Roman (Mansfield, Legge, & Bane, 1996, in Russell-Minda et al., 2007). Courier might
be less readable due to its monospaced width: Every letter in Courier has the same width, as shown in figure 6.

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 28

The quick brown fox jumps over the lazy dog.

Fig. 6: Courier, a monospaced font.

The fonts without serifs, Arial and Comic Sans MS, were significantly easier to read than the fonts with serifs.
However, Bernard et al. (2002) suggest that in fact it is not the presence or absence of serifs that causes this
difference, but the x-height of the font. The x-height may be defined as the height of the ‘torso’ for letters. The x-height
for Times New Roman and Courier is smaller than in Arial and Comic Sans MS, when comparing the fonts in equal
point sizes. In point size 12, the x-height of Times New Roman and Courier is 2.0 mm, in point size 14 it is 2.5 mm;
while in Arial and Comic Sans MS point size 12 the x-height is 2.5 mm and in point size 14 no less than 3.0 mm.

Yet it is not only x-height that determines a letter’s readability. In a comparison between Times New Roman point size
12 and Arial point size 10, having approximately the same x-height (2.0 mm), Times New Roman turned out to be the
least readable font (Bernard et al., 2003). This shows that x-height is not exclusively responsible for the observed
difference between fonts’ legibility. There seems to be an interaction between x-height and other features. Serifs are
one of these features, as well as spacing (the space between the letters) and an underestimated influence: familiarity.
Getting accustomed to a font, or being trained using a font, also affects the readability for an individual. But in this
experiment familiarity did not seem to be the factor making the difference: In a questionnaire, 57% of the participants
stated that they used Times New Roman as their default font, while the results show that Arial was preferred over
Times New Roman. Any familiarity effect would have been in favour of Times New Roman, but this was not the case.
More evidence on this case comes from Campbell et al. (2005; in Russell-Minda et al., 2007), who compared Times
New Roman and an unmodified sans serif font ‘Adsans’. Among 398 participants, a significant majority found Adsans
more readable than Times New Roman.

Russell-Minda et al. provide a review article in which they compare several results regarding serifs and readability
(2007). In general the preference of the reader goes to fonts without serifs (Perera, 2001, in Russell-Minda et al.,
2007), but the results regarding reading speed are inconclusive: Some experiments found significant effects in reading
speed (Yager, Aquilante, & Plass, 1998, in Russell-Minda et al., 2007) while others did not find any effects (Arditi &
Cho, 2005; Moriarty & Scheiner, 1984, in Russell-Minda et al., 2007). In several cases, reading performance improved
for fonts without serifs (Morris, Aquilante, Yager, & Bigelow, 2002, in Russell-Minda et al., 2007; Perera, 2001, in
Russell-Minda et al., 2007, Yager et al., 1998, in Russell-Minda et al., 2007).

Overall, typefaces without serifs, such as Arial, Comic Sans MS, Helvetica and Verdana seem to be more readable
than typefaces with serifs (Russell-Minda et al., 2007). The x-height also contributes to the legibility of text (Bernard et
al., 2003). But the central question is: What do poor readers, more specific dyslexics, benefit from?

Particularly helpful for dyslexics is making letters distinctive (Arditi & Cho, 2005; Bernard et al., 2002; Lockhead &
Crist, 1980), making it easier to discriminate between letters. With this in mind, several individuals or organisations
began developing their own typefaces, especially developed for dyslexics or people with impaired vision. One of these
typefaces designed for visually impaired people is the large-print Tiresias (figure 7), which was found more legible
than Times New Roman and Arial (Perera, 2001; in Russell-Minda et al., 2007). However, only the people who
actually had a visual impairment preferred Tiresias over the other typefaces. The participants with good vision did not
prefer Tiresias as much as their visually impaired co-participants.

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 29

The quick brown fox jumps over the lazy dog.

Fig. 7: The large-print Tiresias font, or LP Tiresias.

Two typefaces exclusively designed for dyslexics, are OpenDyslexic (Gonzalez, 2011) and Dyslexie (Boer, 2009),
shown in figure 8.

Fig. 8: Typefaces especially designed for dyslexics: OpenDyslexic (top) and Dyslexie (bottom).

In the OpenDyslexic font the letters are warped differently: The base of the font is heavier than it is in regular fonts.
This particular form makes the letters more distinctive, which is in line with the earlier discussed research (see figure
5). For example, the b, d, p and q are quite similar in regular fonts, but in OpenDyslexic these letters are more
distinct; mostly because of their heavier base. Furthermore, the b and d are different because the b is more rounded,
and the p and q are made distinct from each other by adding a little block on the q’s tail.
Boer (2009) also made these four letters distinctive in his self-created font Dyslexie, as shown in figure 9. The q in
Boer’s typeface is clearly the most distinct from the other three, making the p more distinctive as well, as it is no
longer interchangeable with q. The b and the d are shaped differently: the b’s bowl having a heavier base, while the
top of the d’s bowl is broader.

Fig. 9: Typefaces OpenDyslexic (top) and Dyslexie (bottom).

Gonzalez added more features to his OpenDyslexic font: When used in web browsers, the punctuation marks are
darker than the letters and the background lights up as the cursor is being moved over the text (figure 10).

Fig. 10: The web browser’s background lights up when the cursor is moved over the text using OpenDyslexic.

The characteristics of Boer’s font Dyslexie include a heavier base of the letter, as well as increased openings in
letters, all enhancing legibility. Furthermore, the x-height of the letters is larger than in most other fonts, some letters
are slightly tilted, capitols and reading signs are more bold in comparison to the other letters, there is more spacing

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 30

between the letters and resembling letters differ in form, such as the b and the d. This line of characteristics is largely
in agreement with results of research into readability. Lockhead and Crist already mentioned making letters distinctive
back in 1980, while more recent research shows that the x-height indeed plays a role in readability (Bernard et al.,
2003).

The font Dyslexie has been researched by two Dutch students, who independently wrote their master’s theses about
this font. De Leeuw (2010) compared Dyslexie to Arial in an experiment testing reading speed and the amount of
errors made among 43 participants, using two well-known Dutch tests; the EMT (Brus & Voeten, 1979) and the Klepel
(Van den Bos, Lutje Spelberg, Scheepstra, & De Vries, 1994). The EMT, short for Een-Minuut-Test (one-minute-test),
is a test that measures technical reading of words. The Klepel is a similar test, but this test consists of pseudo-words.
De Leeuw (2010) found that reading speed increased for neither dyslexics nor typically developing participants when
reading in the Dyslexie font. However, the dyslexics made fewer errors in the EMT when reading in the Dyslexie font
compared to Arial. De Leeuw makes the assumption that the Dyslexie font is beneficial for dyslexics, but for dyslexics
only and it is not enhancing readability for typically developing readers. The results of De Leeuw’s questionnaire
support this statement partially: 71.4% of the dyslexics found the font more low-key than Arial, while 45.5% of the
typically developing readers shared this opinion. Of this latter group, 36.4% found the font easier to read compared to
Arial. Only 42.9% of the dyslexics thought Dyslexie was easier to read. On the other hand, 22.7% of the typically
developing readers were under the impression they made more errors using the Dyslexie font, as opposed to 9.5% of
the dyslexics. Twenty-one dyslexics and twenty-two non-dyslexics took part in the experiment, with an age ranging
from 19 to 28.

Sturm (2012) also compared the fonts Arial and Dyslexie, taking into account reading speed and fluency. In
addition, she also looked into the difference between Dutch and English texts. Fifteen dyslexics and fifteen non-
dyslexics participated in her experiment, age ranging between 14;5 and 16;7, education level vmbo (preparatory
middle-level vocational education). Her results were similar to De Leeuw’s (2010); both dyslexics and typically
developing readers did not particularly benefit from the Dyslexie font in both reading speed and fluency. Moreover,
even more errors were made using the font Dyslexie compared to Arial in the English texts. Sturm attributes these
results to Dyslexie’s heavier base and its ‘messy look’, similar to visual noise.

In both De Leeuw (2010) and Sturm (2012), reading speed clearly does not improve with the font designed
especially for dyslexics. Accuracy, however, might be positively affected by Dyslexie. De Leeuw focused her research
on single, isolated words, while Sturm used words in context, coherent texts. The two experiments were conducted
from different angles, but produced similar results.

Kuster, Braams and Bosman (2012) conducted another experiment comparing Dyslexie to Arial. They had more
participants at their disposal; 163 dyslexic primary school pupils took part in the experiment. But again, the choice of
font did not significantly affect both reading speed and accuracy. The only small differences that were found are likely
to be attributable to a repetition effect.

Finally, dyslexia researcher Ossen tested 39 primary school pupils in comprehension, technical reading and writing,
using the Dyslexie font compared to Arial (2012). What distinguishes her research from the other experiments
described above, is that Ossen actively trained these pupils in reading with Dyslexie. The results are more promising
than the results from the previously described research: Reading speed increased for 31 out of 39 participants, and
the mean number of errors in Dyslexie was 21.4 compared to 27.6 in Arial. Unfortunately, Ossen does not report how
long these texts were, so these numbers are hard to interpret. Besides these results, 75% of the pupils stated to be
positive about the new font. However, Ossen did not support these results with any statistics, making these numbers

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 31

rather unreliable. Moreover, the description of the experiment lacks details, which makes replicating the experiment
practically impossible. And on top of that, Ossen wrote this article while working for the company selling the Dyslexie
font, indicating a possible conflict of interest. Although at first sight the results seem promising, this experiment is not
scientifically objective and independent and therefore unreliable.

Typefaces have been researched for years. Nevertheless, there is still research to be done: Fonts especially designed
for dyslexics might be of little help, but the results so far were not convincing. More research is needed to gain insight
on readability and legibility, and perhaps to help font developers to fine-tune their typefaces in order to be facilitating
for dyslexics.

3.2.2.2 Font size
Being inextricably linked to font type, font size has already been mentioned in the previous paragraph. Bernard et al.
(2002) stated that x-height, the height of the torso of the letter (figure 11), affects readability more than the presence
or absence of serifs. Moreover, the x-height of the typeface is claimed to be a better determinant of its readability than
point size (Bernard et al., 2002). Generally, readability is increased by a larger x-height. But having too large of an x-
height may again decrease readability. Arial is considered a better typeface for dyslexics, not only because of the
absence of serifs, but also because of the enlarged x-height (2.5 mm in point size 12) compared to Times New
Roman (2.0 mm in point size 12).

Fig. 11: X-height in Times New Roman (top) and Arial (bottom).

Besides x-height, Bernard et al. suggest that a point size of 12-14 is most appropriate for children, although the results
in their experiment showed that point size did not significantly affect reading performance (2003). For normal readers,
a point size of 9-14 is best for the usual reading distance of 40 centimetres, while readers with low vision are better
off with a point size of 16-18 (Russell-Minda et al., 2007). It is generally accepted that a larger print or point size is
better for dyslexics, poor readers or people with low vision (Bernard et al., 2003; Martelli et al., 2009; Russell-Minda et
al., 2007; Stein & Walsh, 1997). This is not only supported by objective, strong empirical evidence, but also by
subjective information gathered by questionnaires (Bernard et al., 2003), in which point size 12 is preferred over point
size 10. Stein and Walsh (1997) link visual reading errors to the magnocellular theory. When dyslexics are given a
larger print, they make less reading errors. A larger print size makes text more readable because of dyslexics’ poor
binocular control (Cornelissen et al., 1995; Stein & Walsh, 1997)

Researchers are clear about print size: Dyslexics benefit from a larger print size, but the question arises to which
extent print should be enlarged. Russell-Minda et al. state that the minimum magnification can be measured by critical
print size, which is the smallest print size at which an individual can read at his maximum reading speed (2007).
Besides, critical print size is a frequently used measure to determine the legibility of a typeface. Martelli et al. (2009)
conducted an experiment comparing reading speed in dyslexics and normal controls. The fastest reading rate for

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 32

dyslexics was obtained at a significantly larger print size than the reading speed for controls. However, the reading
rate for dyslexics was still considerably slower than the reading rate for controls, even with enlarged print size: ca. 40
words per minute for dyslexics versus 110 words per minute for controls (Martelli et al., 2009). According to Martelli et
al., “the critical print size for obtaining the maximum reading rate was larger for dyslexics than controls, indicating
abnormal crowding” (2009, p. 14). This indicates once again that dyslexia is a multidisciplinary deficit, which cannot
simply be reduced to one single problem. Crowding takes the discussion from print size to spacing.

3.2.2.3 Spacing
The term ‘spacing’ can be used for both interletter spacing and interline spacing, which is also known as leading
(Russell-Minda et al., 2007). In this paragraph, it generally refers to interletter spacing; the spacing between letters.

Before moving on to the concept of crowding, some general views on spacing are provided. Perrera (2001, in Russell-
Minda et al., 2007) states that people with low vision prefer enlarged spacing. Moreover, bigger spacing increases
legibility (Arditi & Cho, 2005; Bernard et al., 2003). Times New Roman’s narrow spacing, for example, possibly makes
it more difficult to read, especially on a computer screen (Bernard et al., 2003).

However, not all research into spacing has been as positive as these examples. Chung (2002, in Russell-Minda et al.,
2007) carried out an experiment in which several letter spacings were compared. The participants did not have
dyslexia, but had low vision. In this experiment, increased spacing beyond the standard size did not have a significant
effect on reading speed. Moriarty and Scheiner (1984, in Russell-Minda et al., 2007) did not find a significant effect
either. But more recent research opposes these findings and sheds new light on facilitating dyslexia by means of
spacing, as described below.

The required distance between letters, in order for the letters to be readable, is called the ‘critical spacing’ (Martelli et
al., 2009). Critical spacing is defined by measuring the distance between the centres of two adjacent letters. Dyslexics
need a larger space between two adjacent letters than typically developing readers in order to identify a letter (Martelli
et al., 2009). An example of how a dyslexic may perceive a sentence is given in figure 12. Clearly, spacing is only one
of the problems illustrated in this figure: The letters are distorted and blurred, reversed (‘worbs’) and superimposed
(‘for several different’) (Stein & Walsh, 1997).

Fig. 12: Letter reversals, distortion and blurring, superimposition (Stein & Walsh, 1997).

This mixing of letters, the jumbling and the overlap, is called crowding. One of the first researchers to describe
crowding, is Bouma (1970). Martelli et al. define crowding as “the impaired recognition of a target due to the presence
of neighbouring objects in the peripheral visual field” (2009, p. 2). Zorzi et al. take it one step further by appointing
spacing as the core of the problem, stating that crowding is “a perceptual phenomenon with detrimental effects on
letter recognition that is modulated by the spacing between letters” (2012, p. 11455). In other words, the neighbouring
letters are interfering with the target letters, making letter recognition difficult and therefore making word recognition
even more difficult (Martelli et al., 2009). Zorzi et al. (2012) also state that this letter recognition is particularly impaired
when the space between letters is smaller than the critical spacing. But when spaces become too large, they may also
have an impeding effect on reading.

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 33

Martelli et al. state that for dyslexics, identifying letters is particularly difficult in the peripheral visual field (2009). In an
ideal world, spacing and print size would therefore be bigger in the peripheral visual field than in the foveal field.
Unfortunately, with the current technology and knowledge, facilitating this is practically impossible. It would require a
system that tracks the readers’ eye movements and simultaneously spaces the text accordingly. An exaggerated
example of this idea is shown in figure 13.

Fig. 13: Ideal spacing when the focus is on ‘centre’.

The text would constantly change, in accordance with the readers’ eye movements. Apart from the question of
practicality, it is also the question whether this constantly changing visual field is helpful at all.

Crowding is not just a term applicable to dyslexics: It also affects the peripheral vision of normal readers. Because it
only takes places in the peripheral zones, normal readers usually do not experience any difficulties. However, for
dyslexics, it does not only affect the peripheral zones of vision but also the central vision, thereby impeding letter
identification, causing a lower reading speed and a lower reading accuracy (Zorzi et al., 2012). Dyslexics also need a
higher number of eye fixations than normal readers, which causes them to grow tired of reading more easily than
normal readers (Martelli et al., 2009).

Arditi, Knoblauch, and Grunwald (1990, in Russell-Minda et al., 2007) found crowding effects, as well as Morris et al.
(2002, in Russell-Minda et al., 2007), who made the connection between crowding and typeface, stating that crowding
effects are worse for poorly rasterised fonts than for well-rasterised fonts. The rasterisation of fonts is best explained
by an example; poorly rasterised fonts lose their quality when zooming in, while well-rasterised fonts maintain their
quality (figure 14).

Fig. 14: The difference between well rasterised and poorly rasterised text.

Zorzi et al. carried out an experiment in which they showed that manipulated spacing improved reading performance
(2012). In their within-subject experiment, 74 dyslexics were asked to read lines of text. There were two kinds of text;
normal-spaced text (Times New Roman, point size 14) and large-spaced text (Times New Roman, point size 14,
spacing +2.5) (figure 15). Interline spacing (or leading) was also applied to maintain the right proportions between
lines and text. The results encouraged spacing: In the spaced-text condition, the reading performance of dyslexic
children significantly improved. For the controls, the normal readers, there was no significant difference in reading
performance when larger spacing was applied. According to Zorzi et al., “[t]his finding suggests that increased
crowding is most likely a fundamental deficit in dyslexia that can be specifically improved by increasing interletter
spacing” (2012, p. 11456).

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 34

This text is in Times New Roman, regular spacing

This text is in Times New Roman, spacing +2.5

Fig. 15: Lines of text in regular spacing (top) and +2.5 (bottom).

Finally, graph 1 shows the two reading conditions of Zorzi et al.’s experiment, normal (Times New Roman with normal
spacing) and spaced (Times New Roman with 2.5 extra-large spacing). Zorzi et al. compared Italian dyslexics and
French dyslexics to reading-level controls (RL). The graph shows that under normal conditions, the reading-level
controls produce a significantly lower number of errors than the dyslexics. For the reading-level controls, reading
accuracy slightly increases under spaced conditions, but not significantly. For the dyslexics though, the extra-large
spacing increases their reading accuracy to such an extent that their reading accuracy is almost as good as the
reading accuracy of reading level-controls. Although the term ‘reading-level controls’ suggests that these children’s
scores should be similar to the dyslexics’ scores, the difference observed here is supporting the hypothesis of
crowding: Dyslexics have more difficulties reading accurately under normal conditions than reading-level controls;
children who would normally read on the same level. However, under spaced conditions, the observed difference
disappears: Apparently, dyslexics are disadvantaged by crowding, but when spacing is enlarged, their reading
accuracy becomes similar to that of reading-level controls.

Graph 1: Reading accuracy in Italian dyslexics, French dyslexics and reading-level (RL) controls, under normal and spaced conditions (Zorzi
et al., 2012, p.11457).

Extra-large spacing seems to have a positive effect on facilitating dyslexic readers. It would be even better if spacing
could be “optimized adaptively on an individual basis” (Zorzi et al., 2012, p. 11458).

3.2.2.4 Contrast and colour
Dyslexics have a reduced luminance sensitivity (Cornelissen et al., 1995) and a reduced motion sensitivity (Ray,
Fowler, & Stein, 2005), likely to be caused by a deficit in the magnocellular system. According to Chase,

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 35

Ashourzadeh, Kelly, Monfette and Kinsey (2003) the problems which dyslexics encounter are caused by “an
abnormally large L-cone to M-cone ratio in their magnocellular surrounds” (Chase et al., 2003, in Ray et al., 2005, p.
286). Cone cells are cells located in the retina of the eye. They are able to perceive fine details, rapid changes and
they are the cells responsible for colour vision. There are three types of cones: S-cones (short), M-cones (medium)
and L-cones (large). Each cone is sensitive for different wavelengths; S-cones absorb blue colours, M-cones absorb
green colours and L-cones absorb red colours. Chase et al. (2003) claim that for dyslexics, the balance between these
three types of cones is disturbed: They have substantially more L-cones than M-cones compared to a typically
developing reader.

Trying to replicate research into luminance sensitivity, Cornelissen et al. (1995) tested whether dyslexics’ luminance
sensitivity is indeed reduced. They tested dyslexics’ contrast sensitivity under photopic luminance conditions, i.e. well-
lit conditions (as opposed to scotopic vision, i.e. low-light conditions). Earlier research showed reductions in dyslexics’
contrast sensitivity under mesopic luminance conditions, i.e. a combination of photopic and scotopic vision; low but not
yet dark lighting (Lovegrove et al., 1982, in Cornelissen et al., 1995). Cornelissen et al. (1995) found that under
photopic luminance conditions, the difference in contrast sensitivity reduction between dyslexics and controls is
negligible. In other words; under ideal lighting circumstances, there seems to be no significant difference between
dyslexics and normal controls.

The reduced motion sensitivity, as described in 3.2.2.3 and illustrated by figure 3, caused by a magnocellular deficit
(Newsome & Paré 1988; Ray et al., 2005), may be neutralised by yellow filters. Blue input is said to impede the
magnocellular pathway, but a yellow filter may boost magnocellular cell activity and neutralise this effect. Ray et al.
(2005) found that yellow filters increased motion sensitivity, convergence and accommodation, with and without a
training period. Magnocellular cells are sensitive to yellow and are being inhibited by blue. Hence, when yellow filters
are applied, short wavelengths are being cut out and the relative ratio of L-cone and M-cone influence is normalised,
increasing the efficiency of magnocellular cells (Ray et al., 2005). When this efficiency increases, the magnocellular
pathway improves and as a result, yellow filters may benefit the dyslexic reader. This hypothesis was tested in an
experiment by Ray et al. (2005), in which 38 poor readers, different groups of children, participated. In a series of
experiments, they were given either a yellow filter, a neutral control filter or a placebo filter. In a first reaction, the
participants stated that the yellow filters improved the clarity of the text. One experiment proved that yellow filters
improved motion sensitivity and, hence, improved magnocellular functioning without any training (Ray et al., 2005). In
the experiment that included a training period of three months, reading ability significantly increased for the
participants using yellow filters, not for the placebo group (Ray et al., 2005).

However, Skottun and Skoyles (2007) criticise Ray et al.’s (2005) approach. They argue that the magnocellular system
is not equal to the luminance system and that Ray et al. (2005) wrongly assume that S-cones are inhibitory to the
magnocellular system. Skottun and Skoyles (2007) state S-cones are excitatory instead of inhibitory, and therefore the
theoretical framework of Ray et al.’s research (2005) is inadequate.

An experiment by Estey, Jeremy and Jones (1990, in Russell-Minda et al., 2007) showed that out of blue, green and
black text on a white background, black text on white background is preferred. In an experiment where critical
contrasts were measured, the results showed that dyslexics obtained the same critical contrast as typically developing
readers (O’Brien, Mansfield, & Legge, 2000, in Martelli et al., 2009). Yager et al. (1998, in Russell-Minda et al., 2007)
found that low luminance generally affects reading speed.

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 36

3.2.3 Summary of theoretical perspectives

In the first part of this thesis’ theoretical part, theories attempting to explain dyslexia were discussed. First of all, the
phonological deficit hypothesis, which describes a deficit that accounts for an impaired grapheme-phoneme
correspondence (Ramus et al., 2003), problems in word identification, phonological awareness, letter-sound decoding,
rapid naming and verbal memory (Vellutino et al., 2004). Gough and Tunmer (1986) presented reading comprehension
as a mathematical formula (figure 1).

Taken together with a deficit in processes underlying naming speed, the phonological deficit hypothesis
forms the double-deficit hypothesis (Wolf & Bowers, 1999). This hypothesis consists of two separable hypotheses, but
when they occur together, as they do in the double-deficit hypothesis, they may cause major reading impairment (Wolf
& Bowers, 1999).

The rapid auditory processing hypothesis describes a deficit in perception of short or rapidly varying sounds
(Tallal, 1980). Results improve when spaces between stimuli are increased (McAnally et al., 2000) like spacing in
written text (Martelli et al., 2009).

In the visual deficit hypothesis, a difficulty processing words on a page of text is described (Ramus et al.,
2003). Getman (1985, in Vellutino et al., 2004) suggests an oculomotor deficit is the cause for visual tracking
problems.

The cerebellar deficit hypothesis is a theory describing a cerebellar deficit that accounts for a small part of
dyslexics’ problems, such as having difficulties balancing, poor automatisation skills and poor motor skills (Nicolson et
al., 2001).

An interaction between the hypotheses mentioned above is the magnocellular theory (Ramus et al., 2003).
The theory assumes a deficit or a reduced sensitivity in the magnocellular system, which tracks eye movements
during reading and is responsible for binocular control and maintaining focus during saccades (Livingstone et al.,
1991; Skottun, 1998; Stein, 2001; Stein & Walsh, 1997; Vellutino et al., 2004).

The noise-exclusion hypothesis does not assume a magnocellular deficit, but a deficit in visual noise-
exclusion instead (Sperling et al., 2006). Taken together with a deficit in signal enhancement, a noise-exclusion deficit
affects the dyslexic’s perception (Sperling et al., 2006).

Besides these hypotheses, this first theoretical part also described dyslexia and comorbidity, dyslexia from an
evolutionary perspective, dyslexia linked to genetics and dyslexia’s side effects. In the second theoretical part, a shift
from internal factors to external factors was made. In this paragraph about facilitating dyslexia and typographical
effects, the focus is on textual features and typographical alterations, beginning with font type. The absence or
presence of serifs may make letters distinctive (Lockhead & Crist, 1980) or act as a form of visual noise (Arditi & Cho,
2005). This idea of visual noise is shared by the perception noise exclusion hypothesis (Sperling et al., 2006), which
hypothesises that dyslexics have performance deficits in tasks with a high level of external noise, both magnocellular
and parvocellular (Sperling et al., 2006). Other textual features such as width and x-height were discussed, the latter
increasing readability when enlarged in fonts (Bernard et al., 2002), and two typefaces developed exclusively for
dyslexics were discussed: Dyslexie (Boer, 2009) and OpenDyslexic (Gonzalez, 2011). In two studies comparing
Dyslexie to regular typefaces, there was no significant difference between the two fonts (De Leeuw, 2010; Sturm,
2012).

Dyslexics generally benefit from a larger font size (Bernard et al., 2003; Cornelissen et al., 2005; Martelli et
al., 2009; Russell-Minda et al., 2007; Stein & Walsh, 1997). Enlarged interletter spacing decreases the amount of
crowding and enhances legibility (Arditi & Cho, 2005; Bernard et al., 2003; Martelli et al., 2009; Perrera, 2001, in
Russell-Minda et al., 2007; Zorzi et al., 2012).

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 37

According to Ray et al., there is a magnocellular deficit responsible for reduced motion sensitivity (2005).
This motion sensitivity may be improved by applying yellow filters (Ray et al., 2005), but this suggestion is criticised by
Skottun and Skoyles (2007). When it comes to contrasts, black text on white background is preferred (Estey et al.,
1990, in Russell-Minda et al., 2007).

In the following chapter, the most important results will be linked to this thesis’ experiment.

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 38

4 The experiment

Dyslexia is regarded as a reading disability which can be facilitated in many ways. These ways of facilitation range
from applying larger font sizes to increased spacing and from monocular occlusion to coloured filters, depending on
the adopted theoretical framework. In this experiment, two groups of dyslexics were compared to each other in an
experiment in which three textual features were altered: font size, interletter spacing and interline spacing (leading).
These features were selected for two main reasons: 1) research literature elaborately describes them as facilitating for
dyslexics when they are enlarged, and 2) these features could be altered in the TOA, the digital environment in which
the dyslexics were tested, after special software was developed.

The central question in this experiment is:

Research question
- To what extent can textual adaptations make a difference in dyslexics’ reading comprehension?

To answer this question, the following hypotheses, based on the literature review in chapter 3, were tested in this
experiment:

Hypotheses
1) Dyslexics’ reading comprehension scores are higher when font size, interletter spacing and interline spacing are

increased.
2) Dyslexics find it easier to read when font size, interletter spacing and interline spacing are increased.

The first hypothesis is tested in an experiment. The dyslexics’ opinion, as described in the second hypothesis, is
measured by a questionnaire.

4.1 Participants
Thirty-nine vmbo-students (‘voorbereidend middelbaar beroepsonderwijs’, literal translation ‘preparatory middle-level
vocational education’) (32 male, 7 female, mean age 14;5, range 12;4 to 15;6) of two secondary schools in the The
Hague/Voorburg region participated in this study. They were all diagnosed with dyslexia or the teachers strongly
suspected dyslexia. Twenty-four participants were in the first year, fifteen participants were in the second year. The
participants were not given a grade for the test but they were told it was ‘a test’ they were making, without any further
remarks about grading. One participant from the experimental group did not finish the test because he ‘was unable to
read the small letters’; this participant was excluded from further analyses.

4.2 Material and design
A reading test was selected from the TOA, Nederlands Lezen 2F toets 1 (Dutch Reading 2F test 1). The test contains
eight texts varying in length, and 20 multiple-choice questions. The 2F level of the Meijerink Framework of Reference
(Expertgroep Doorlopende Leerlijnen Taal en Rekenen, 2008) is roughly comparable to the B1 level of the Common
European Framework of Reference for Languages (Council of Europe, 2008). The participants made the test in the
web-based TOA, which was already a familiar online environment for them. They were divided into two groups, taking
into account previous test scores of another reading test (Nederland Lezen 1F-2F Jongeren, Dutch Reading 1F-2F
Youngsters) to create two similar, comparable groups. An independent t-test, based on these test scores, was
performed to make sure the two groups were indeed similar and comparable. The control group

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 39

(16 male, 3 female, mean age 14;6) did not differ statistically from the experimental group

(15 male, 4 female, mean age 14;4); .

There were two test conditions: a ‘normal’ test condition in which the selected test was presented as it is currently
presented in the TOA, based on the default settings of the TOA (Verdana 8.5 pt or 11 px, interletter spacing 0 pt/px,
interline spacing +1.0 pt or 16 px), and an experimental test condition in which the textual features were altered to
Verdana 10 pt or 13 px, interletter spacing +0.5 pt or 1 px, interline spacing +1.15 pt or 19 px. Interline spacing was
altered to maintain a clear overall picture of the text. Each group was assigned to one test condition, making it a
between-subject design. By using a between-subject design, any learning effects are being prevented and the
participants only need to take one test. Examples of the two versions of the test are provided in the appendices (I and
II).

The participants also filled in a questionnaire. In the questionnaire they were asked about their opinion of the test,
whether they experienced any difficulties making the test, how they felt about the typeface and font size and to what
extent dyslexia disabled their reading skills. The full questionnaire is provided in appendix III.

4.3 Procedure

The test took place in three sessions in the computer labs of the participants’ schools and the circumstances were
equal for each participant. The participants first listened to an instruction about how to log in and that they were about
to make a reading test. The web-based tests were made individually and each participant had the same amount of
time to complete the test. After the test, each participant filled out the paper-based questionnaire.

4.4 Analysis

In an experimental design, one independent variable (textual adaptation) and one dependent interval variable (test
score ranging from 0-100), an independent t-test was carried out to compare the groups, using SPSS. All assumptions
for an independent t-test have been met: There is interval data, the two groups are independent, the observations
were independent, there are no significant outliers, the Kolmogorov-Smirnov test confirmed that the data are normally
distributed and Levene’s test, testing the homogeneity of the variances, was non-significant, meaning we can assume
that the variances are roughly equal and that this assumption has been met.

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 40

5 Results

5.1 Results of the experiment
The results of the reading test used in the experiment ( , mean score, standard deviation) are displayed in table 3.

Mean score Standard deviation Standard error
3.595
control group 19 50.526 15.670 5.277

experimental group 19 55.000 23.004

Table 3: Results of the reading test Nederlands Lezen 2F toets 1 (Dutch Reading 2F test 1).

A two-tailed independent t-test was conducted to compare test scores between the control group (normal textual

features) and the experimental group (altered textual features). On average, the experimental group obtained higher

scores than the control group . However, this difference was not

significant; . When applying a one-tailed t-test, the difference was still not significant

( ).

5.2 Results of the questionnaire

The questionnaire (appendix III) was composed of five different questions that could be answered on a Likert scale.
The questions were:

1) To what extent are you bothered by dyslexia?
2) How easy/hard was the test for you?
3) How did you experience reading in this typeface?
4) What did you think about the size of the letters?
5) Did you get tired of reading this test’s texts?

Each participant filled in the questionnaire directly after making the reading test. The results of the questionnaires are
displayed in tables 4-8.

1. To what extent are you bothered by dyslexia?

not at all a little quite a lot a lot

control group 21.06% 57.89% 15.79% 5.26%

experimental group 10.53% 52.63% 36.84% 0.00%

Table 4: Frequency counts of the question ‘To what extent are you bothered by dyslexia?’.

There were twice as many participants who ticked the ‘not at all’-box in the control group compared to the
experimental group. ‘A little’ was selected by a more than 50% for both groups. There were almost twice as many
responses for ‘quite a lot’ in the experimental group as in the control group. Nobody in the experimental group
selected ‘a lot’, 5.26% of the control group ticked this box.

2. How easy/hard was the test for you?

very easy quite easy normal quite hard very hard

control group 5.26% 10.53% 47.37% 36.84% 0.00%

experimental group 0.00% 10.53% 52.63% 31.58% 5.26%

Table 5: Frequency counts of the question ‘How easy/hard was the test for you?’.

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 41

The two extremes ‘very easy’ and ‘very hard’ were hardly selected. An equal percentage in both groups chose ‘quite
easy’. The neutral choice ‘normal’ was selected by roughly half of the participants. The control group ticked the box
‘quite hard’ a little more often than the experimental group.

3. How did you experience reading in this typeface?

very easy quite easy normal quite hard very hard

control group 10.53% 0.00% 63.15% 26.32% 0.00%

experimental group 10.53% 47.36% 31.58% 10.53% 0.00%

Table 6: Frequency counts of the question ‘How did you experience reading in this typeface?’.

An equal part of both groups found reading in this typeface ‘very easy’: 10.53% selected this option. Almost half of the
experimental group’s participants ticked the box ‘quite easy’, nobody in the control group ticked this box. The option
‘normal’ was chosen by 63.15% of the control group and 31.58% of the experimental group. More participants in the
control group than in the experimental group selected ‘quite hard’. There were no participants who selected ‘very hard’
in response to the question how they experienced reading in this typeface.

4. What did you think about the size of the letters?

way too small a little too small just right a little too large way too large

control group 10.53% 36.84% 47.37% 5.26% 0.00%

experimental group 0.00% 26.32% 63.16% 5.26% 5.26%

Table 7: Frequency counts of the question ‘What did you think about the size of the letters?’.

Nobody in the experimental group thought the size of the letters was ‘way too small’. There were more participants in
the control group than in the experimental group who chose ‘a little too small’. The majority of the experimental
group’s participants selected ‘just right’ (63.16%), less than half of the control group’s participants selected this option.
An equal amount of participants in both groups chose ‘a little too large’, the same number of the experimental group
selected ‘way too large’. No participants in the control group chose this option.

5. Did you get tired of reading this test’s texts?

not at all a little quite a lot a lot

control group 26.32% 36.84% 31.58% 5.26%

experimental group 10.53% 36.84% 36.84% 15.79%

Table 8: Frequency counts of the question ‘Did you get tired of reading this test’s texts?’.

There were more participants in the control group who selected ‘not at all’ than in the experimental group. ‘A little’ was
chosen by 36.84% in both groups, which was the same percentage that selected ‘quite a lot’ in the experimental
group. The amount of participants in the experimental group who selected ‘a lot’ was three times larger than in the
control group.

These results will be further discussed in the next chapter.

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 42

6 Discussion and conclusion

The results of both the experiment and the questionnaire will be interpreted in this chapter. First, the results of the
experiment will be discussed and compared to the expectations as stated in the hypothesis. Subsequently, the results
of the questionnaire will be discussed likewise, working towards an answer to the research question: ‘To what extent
can textual adaptations make a difference in dyslexics’ reading comprehension?’.

6.1 The experiment

The goal of this experiment was to find out whether dyslexics obtain better test scores on reading comprehension

tests when textual features such as font size, interletter spacing and interline spacing are increased. The results of the

independent t-test did not show a significant effect between the independent variable ‘reading condition’ and the

dependent variable ‘test score’ , although the experimental group did obtain higher scores

than the control group .

Remarkable about these results are the high standard deviations of the groups (table 3), meaning there is a lot of
variance in both groups. The experimental group’s standard deviation is particularly high. To explain this high
variance, a closer look was taken at the two schools where the experiments were carried out. When comparing the
descriptive statistics of both schools, it becomes clear that this high standard deviation is particularly high in the
second school’s experimental group (table 9 & 10).

Mean score Standard deviation Standard error
5.540
control group 9 50.556 16.620 4.676

experimental group 8 56.563 13.225

Table 9: Descriptive statistics of the first school where the experiment was carried out.

Mean score Standard deviation Standard error
4.955
control group 10 50.500 15.670 8.669

experimental group 11 53.863 28.752

Table 10: Descriptive statistics of the second school where the experiment was carried out.

Although the circumstances were equal for these participants, the scores are still far apart, the highest being 95.00
and the lowest 17.50. The two individuals with these extreme results were both in their second year and the same
goes for the rest of the group, when observing the other results. In other words, the educational levels do not explain
the high variance. An independent t-test was carried out before the experiment to test whether the control group and
the experimental group were comparable, taking into account previous test scores. Since the groups turned out to be
comparable, between-group differences could not be the reason for this variance.

A logical explanation for this observation would be that this variance is attributable to dyslexia’s complexity
and versatility. Dyslexia comes in all shapes and sizes, meaning dyslexics come in all shapes and sizes too. The
results show a great within-subject variance under equal circumstances and with equal groups. Group size could also
play a role, since for both groups . Increasing usually means reducing variance, although one might wonder if
increasing in this case would solve the problem completely, because of the extremely varying test scores.

The results in this thesis contradict most of the results from the literature reviewed in chapter 3. Linguists
who did find significant effects in comparable experiments are Arditi and Cho (2005), Bernard et al. (2003),
Cornelissen et al. (1995), Martelli et al. (2009), Russell-Minda et al. (2007), Stein and Walsh (1997) and Zorzi et al.

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 43

(2009). However, Moriarty and Scheiner (1984, in Russell-Minda et al., 2007) and Chung (2002, in Russell-Minda et
al., 2007) were not able to find significant effects either.

The expectations regarding the experiment’s outcome were phrased in the first hypothesis, stated in chapter 4:

1) Dyslexics’ reading comprehension scores are higher when font size, interletter spacing and interline spacing are
increased.

The results do not confirm this hypothesis. There is a visible trend when observing the mean scores of both groups in

favour of the experimental group , compared to the control group, . However, there was no

significant difference.

6.2 The questionnaire

The goal of the questionnaire was to gain insight of the dyslexics’ opinion about textual features in digital testing. The
questionnaire consisted of five questions, which will be discussed one by one.

In table 4, which appeared in paragraph 5.2 and which is repeated here, the first question of the questionnaire is
shown. This is a general question and unrelated to the test the dyslexics made right before they filled in the
questionnaire.

1. To what extent are you bothered by dyslexia?

not at all a little quite a lot a lot

control group 21.06% 57.89% 15.79% 5.26%

experimental group 10.53% 52.63% 36.84% 0.00%

Table 4: Frequency counts of the question ‘To what extent are you bothered by dyslexia?’.

This question, gauging to what extent dyslexics are bothered or feel restricted by dyslexia, is answered with ‘a little’ by
the majority of the participants. Twice as many dyslexics in the control group compared to the experimental group
stated that they were not bothered at all, while more than twice as many participants of the experimental group
claimed to be bothered by dyslexia ‘quite a lot’. Only 5.26% of the control group’s participants stated to be bothered ‘a
lot’. Some dyslexics had questions about how to answer this question or said they had difficulties describing to what
extent they were bothered by dyslexia. Considering this question we may conclude that the groups are roughly equal
when it comes to being bothered by dyslexia.

The second question ‘How easy/hard was the test for you?’ is shown in table 5.

2. How easy/hard was the test for you?

very easy quite easy normal quite hard very hard

control group 5.26% 10.53% 47.37% 36.84% 0.00%

experimental group 0.00% 10.53% 52.63% 31.58% 5.26%

Table 5: Frequency counts of the question ‘How easy/hard was the test for you?’.

The two most extreme options ‘very easy’ and ‘very hard’ were only selected by very few participants. In both groups,
10.53% chose ‘quite easy’, meaning there was no difference between the groups for this option. ‘Normal’ was chosen
by 52.63% of the experimental group’s dyslexics and 47.37% of the control group’s dyslexics. This is contrary to
expectations, since the experimental group made the test with increased font size, interletter spacing and interline

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 44

spacing and so it was expected for this group to consider the test easier than the control group would. This is the
case for the option ‘quite hard’: 36.84% of the control group chose this option, while 31.58% of the experimental group
ticked this box. Because of the changing tendency of the results between normal - quite hard - very hard, there is no
observable difference between the groups with regard to the question ‘How easy/hard was the test for you?’.

The third question and its frequency count are shown in table 6.

3. How did you experience reading in this typeface?

very easy quite easy normal quite hard very hard

control group 10.53% 0.00% 63.15% 26.32% 0.00%

experimental group 10.53% 47.36% 31.58% 10.53% 0.00%

Table 6: Frequency counts of the question ‘How did you experience reading in this typeface?’.

This question is about how the participants experienced reading in this particular typeface. For both groups, this
typeface was the same, i.e. Verdana. However, for the experimental group the font size was increased and interletter
spacing was applied, which makes the typeface look different. This should be accounted for in the interpretation of this
question: Although for both groups the typeface was identical, the participants may have perceived it quite differently
because of the adapted textual features. For that reason, this question should be considered together with the fourth
question, the question about font size, which is shown in table 7 and repeated below.

About one tenth of the participants thought reading in this typeface was easy, regardless of experimental setting.
However, there is a visible trend in each group, indicating that the control group had more trouble reading in this
typeface compared to the experimental group. This trend is made visible in graph 2.

Graph 2: ‘How did you experience reading in this typeface?’.

An equal amount of participants in each group thought reading in this typeface was ‘very easy’. Nobody in the control
group chose ‘quite easy’, a vast majority selected ‘normal’ and 26.32% chose ‘quite hard’. ‘Very hard’ was selected by
none of the participants. Almost half of the participants in the experimental group considered reading in this typeface
‘quite easy’, almost a third thought it was ‘normal’ and 10.53% selected ‘quite hard’. Comparing these numbers to the
control group, a pattern appears: The control group seems to have more difficulties reading in this particular typeface

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 45

than the experimental group. Since the typefaces were identical but enlarged and therefore possibly perceived
differently, we may conclude that this textual adaptation is considered an improvement by dyslexics.

A similar pattern may be perceived in the responses of the questionnaire’s fourth question.

4. What did you think about the size of the letters?

way too small a little too small just right a little too large way too large

control group 10.53% 36.84% 47.37% 5.26% 0.00%

experimental group 0.00% 26.32% 63.16% 5.26% 5.26%

Table 7: Frequency counts of the question ‘What did you think about the size of the letters?’.

Nobody in the experimental group thought the letters were ‘too small’1, while 10.53% of the control group stated it
was. Another 36.84% of the control group selected ‘a little too small’. Almost half of this group’s participants thought
the font size was ‘just right’, while only one participant thought the text was ‘a little too large’. Comparing these
responses to the experimental group’s responses, there were considerably less participants who considered the text ‘a
little too small’. The great majority of the experimental group’s participants, 63.16%, experienced the font size as ‘just
right’. Both the categories ‘a little too large’ and ‘way too large’ were only selected once. Graph 3 illustrates the
pattern that emerges from these responses.

Graph 3: ‘What did you think about the size of the letters?’.

This graph clearly depicts that there are more participants who considered the text too small in the control group than
in the experimental group. A negligible amount of the participants considered the text too large, meaning the newly
adapted size is not too large for dyslexics. There were less participants in the experimental group who considered the
text too small. Therefore, we may conclude that enlarging the text is a good measure in the dyslexic’s opinion.

Finally, the fifth question ‘Did you get tired of reading this test’s text?’ is shown in table 8.

1 One participant in the experimental group stated the font was size too small, but this participant did not finish the test for this reason and
was therefore excluded from the experiment.

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 46

5. Did you get tired of reading this test’s texts?

not at all a little quite a lot a lot

control group 26.32% 36.84% 31.58% 5.26%

experimental group 10.53% 36.84% 36.84% 15.79%

Table 8: Frequency counts of the question ‘Did you get tired of reading this test’s texts?’.

The options ‘a little’ and ‘quite a lot’ were selected by roughly the same amount of participants for both groups.
Contrary to expectations, there were more participants in the control group who selected ‘not at all’ and more
participants from the experimental group who chose ‘a lot’. These results may be this way because the experimental
setting was new for the participants and therefore more tiring than the normal, unchanged control setting. However,
since the of both groups was 19 and therefore quite small, we would need a larger sample to be able to conclude
that this experimental setting did indeed exhaust the participants.

Having discussed the questionnaires’ results, we may now proceed to answer this experiment’s second hypothesis, as
stated in chapter 4:

2) Dyslexics find it easier to read when font size, interletter spacing and interline spacing are increased.

To test this hypothesis, the questions from the questionnaire, filled in by all 38 participants, were analysed and
discussed. There was no clear difference between the control group and the experimental group with regard to the
question ‘How easy/hard was the test for you?’. The responses to the question ‘Did you get tired of reading this test’s
texts?’ were contrary to expectation: The experimental group seemed to have become more tired of reading than the
control group, therefore not supporting the hypothesis. However, increasing the may provide more reliable results.
The questions about typeface and font size were answered according to expectations: The experimental group’s
participants generally considered reading in this typeface easier and while almost half of the control group’s
participants thought the font size was too small, only a quarter of the experimental group shared this opinion. The third
and the fourth question are particularly about the reading experience and since these two questionnaire items support
the hypothesis, we may – with caution – confirm the hypothesis: Dyslexics find it easier to read when font size,
interletter spacing and interline spacing are increased.

This leads us to the main question of this thesis, as stated in the fourth chapter:

- To what extent can textual adaptations make a difference in dyslexics’ reading comprehension?

To answer this question, an experiment including a reading comprehension test was carried out, and all participants
filled in a questionnaire. As far as test scores are considered, there was no significant difference between the control
group and the experimental group and therefore, in answer to the main question, textual adaptations do not make a
significant difference in dyslexics’ reading comprehension.

However, the questionnaire’s results show that the experimental setting is favoured by dyslexics. The
increased font size, interletter spacing and interline spacing increases legibility: the dyslexics experienced reading in
the experimental setting as ‘easier’ and the number of dyslexics who considered the font size ‘too small’ was reduced
by 50%. The new setting may not have improved dyslexics’ reading comprehension; the dyslexics did rate reading in
the experimental setting as a positive experience.

Another experiment testing dyslexic reading ability in vmbo students was carried out by Sturm (2012), also described
in paragraph 3.2.2.1, whose results were similar. Sturm compared dyslexics and non-dyslexics, taking into account

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 47

reading speed and fluency, with two experimental settings: typefaces Arial and Dyslexie (2012). Her results also
showed no significant difference between typefaces: Both groups of readers did not benefit from the Dyslexie font. In
contrast to this thesis’ experiment, Sturm found that the students reading in the Dyslexie font made even more errors.
In this thesis’ experiment, this was not the case: The dyslexics reading in the experimental setting obtained better test
scores (non-significant). Sturm states that a training period for the dyslexics, familiarising them with the new font,
might positively affect the results. This could affect this experiment’s results as well: Both the control group and the
experimental group had only worked with the TOA in the normal, control setting before. This might have been an
advantage for the control group. The experimental group, on the other hand, made the reading test in an entirely new
setting, a setting they were unfamiliar with. Hence, their results might have been affected. These are, however, only
speculations and further research is needed to support this claim.

Dyslexia is a complex deficit in reading and spelling. All theories described in the literature review of this
thesis have been proved right by one or more experiments, but counterevidence has been found as well. It seems that
dyslexia cannot be captured in one definition, as stated by these theories: its multifactorial character does simply not
allow it. Every dyslexic is unique and as observed in this experiment, there even seem to be differences between
schools. There are great differences between dyslexics, even when external circumstances are equal, as they were in
this experiment. A similar experiment carefully selecting dyslexics, based specifically on how dyslexia has manifested
itself in the dyslexic, could produce more accurate and reliable results. This would allow us to further differentiate
between dyslexics and divide them into even more equal, comparable groups. Furthermore, increasing the number of
participants could reduce the standard deviation, which was relatively high in this experiment. The best experiment
would be a combination of qualitative and quantitative research, including both a higher and a more thorough
process of selecting participants.

Recommendations

Although the experiment’s results were non-significant, based on the questionnaire’s outcome I would recommend to
keep the increased font size, increased interletter spacing and increased interline spacing as an optional feature in the
TOA, the web-based testing environment. The current application of the experimental setting, an ‘increase text size’
button and a ‘decrease text size’ button, is a recommendable setting: The buttons are only available to dyslexics, who
are able to choose whether they want to enlarge the text or not. In this situation, it is not necessarily a change they
need to adapt to, but a choice: it is up to the user whether he wants to use the new setting or not. Since the results
showed that the experimental group’s test scores were equal to, or even higher than (non-significant) the control
group’s test results, it would do no harm to let them choose between these settings themselves. This way, the dyslexic
users of the TOA can be facilitated: by providing additional, textual alteration options in reading tests.

Typographical support for dyslexics: The effect of textual alterations on dyslexics’ test scores A. E. Schoonewelle 48

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