The effect of training synaesthetic letter-color associations on reading and stroop performance in dyslexics

THE

EFFECT

OF

TRAINING

SYNAESTHETIC

LETTER-COLOR

ASSOCIATIONS

ON

READING

AND

STROOP

PERFORMANCE

IN

DYSLEXICS

Master Thesis of Simone Vugts

Department of Psychology, University of Amsterdam

Date:

August 18

th

, 2014

Student:

S.M.A.G. Vugts

Student number:

6144004

Master:

Psychology, Brain and Cognition

Supervisor and assessor:

mw. Olympia Colizoli, MSc

Co-assessor:

mw. dr. Romke Rouw

University of Amsterdam

Department of Psychology, Brain and Cognition

Weesperplein 4, 1018 XA, Amsterdam

2

THE

EFFECT

OF

TRAINING

SYNAESTHETIC

LETTER-COLOR

ASSOCIATIONS

ON

READING

AND

STROOP

PERFORMANCE

IN

DYSLEXICS

Master Thesis of Simone Vugts

3 ABSTRACT

Synesthesia is a phenomenon where input from a certain modality induces an additional experience in another modality which is not normally triggered by the inducer. The most studied type of synesthesia is called grapheme-color synesthesia and involves perceiving colors when seeing letters. In a recently published study a sub-set of traits typically regarded as markers of synesthesia is acquired in non-synesthetes by reading in color, specifically the presence of a ‘synesthetic Stroop effect’ (Colizoli et al. 2012). This study appears to be the first that is letting participants acquire these traits by reading in color. An interesting question is whether these traits can also be acquired by people with dyslexia. Reading in color may be able to enhance features in reading comprehension and could possibly help people with reading difficulties. This project will study whether dyslexics can acquire letter-color associations and compare the effects of these associations with non-dyslexics on a synesthetic Stroop task and different reading comprehension tests.

4

- (De Anima, book II, ii; Wheelwright 1951, p.138)

- Dominc Wills about sir Anthony Hopkins, Oscar winning actor

- Whoopi Goldberg, famous actress

5

Contents

Abstract

…p. 3 1.

Introduction

…p. 8 1.1 Synesthesia …p. 8 1.2 Dyslexia …p. 9

1.3 Key questions & Hypotheses …p. 10

2.

Methodology

…p. 11 2.1 Participants …p. 11 2.2 General procedure …p. 12 2.3 Letter-color preferences …p. 13 2.4 Reading materials …p. 13

2.5 Reading experience dyslexics …p. 13

2.6 Synesthetic consistency tests …p. 14

2.7 Synesthetic Stroop task …p. 14

2.8 Reading speed …p. 15 2.9 Chessboard …p. 16 2.10 Lexical Decision …p. 16

2.11 Reading experience group 1 and 2 …p. 17

2.12 Reading experience group 3 …p. 18

3.

Results

…p. 19

3.1

Reading Speed …p. 19

3.2 Chessboard …p. 21

3.3 Lexical decision …p. 22

3.4 Stroop …p. 23

6

3.6 Reading experience group 1 and 2 …p. 31

3.7 Reading experience group 3 …p. 33

4.

Discussion

…p. 34 4.1 Conclusions …p. 34 4.2 Possible explanations …p. 35 4.3 Limitations …p. 36 4.4 Prior research …p. 37 4.5 Future research …p. 38

Acknowledgments

…p. 39

References

…p. 39

Tables

Table 1. Participants …p. 12

Table 2. Amount of reading and reading speed …p. 19

Table 3. Amount of reading and reading speed per group …p. 20

Table 4. Accuracy Stroop …p. 27

Table 5. The Stroop effect for each participant …p. 29

Table 6. The Stroop effect for each group …p. 30

Table 7. Reading experience questionnaire …p. 32

Figures

Figure 1. Synesthetic Stroop task …p. 15

7

Figure 3. Lexical decision task …p. 17

Figure 4. Reading speed …p. 21

Figure 5. Mean chessboard scores …p. 22

Figure 6. Lexical decision, words vs. non-words …p. 23

Figure 7. RT Congruent and incongruent trials Stroop …p. 24

Figure 8. Reaction times Stroop …p. 26

Figure 9. Accuracy congruent and incongruent Stroop trials …p. 27

Figure 10. Overall accuracy Stroop …p. 28

8

1. INTRODUCTION

1.1 Synesthesia

Imagine, the word combination ‘as if’ tastes like soft served ice cream, a C# note on the violin smells like a garden full of roses and Sunday always looks yellow. These associations sound strange, but are very familiar to people with synesthesia. Synesthesia is a phenomenon where input from a certain modality induces an experience in another modality which is not normally triggered by the inducer, a remarkable way to perceive the world (Colizoli et al., 2012; Ward, 2013).

Until the research of Simner et al. (2006) the most common type of synesthesia was thought to be grapheme-color. In fact, grapheme-color synesthesia appears to be the most studied type, while perceiving colored days is the most common, with a prevalence of 63% among synesthetes (Simner et al. 2006). In general, synesthesia is found in approximately 4% of the population and the grapheme-color subtype is found in 45% among synesthetes (Simner et al. 2006). Of course, co-existence of subtypes and individual differences exist and are important factors to take into consideration (Beeli et al. 2005; Colizoli et al. 2013). For instance, spatial forms of synesthesia are five times more prevalent in grapheme-color synesthetes than in those lacking color features (Ward, 2013). Grapheme-color synesthesia refers to a condition in which colors are perceived when viewing numbers or letters (graphemes) (Brang et al., 2011; Ward, 2013). This subtype of synesthesia demonstrates that the inducer and the experienced sense can occur in the same modality (Ward, 2013).

There is a genetic predisposition for synesthesia and traits can be reported in early childhood (Rouw et al. 2011). The environment however, plays a major role in the development of the particular type of synesthesia. Letter-color associations in grapheme-color synesthetes are generally consistent across the lifespan and are very specific (Brang et al., 2011). It is impossible for these synesthetes to change the color of for instance the letter ‘n’ that is always luminous red (Ward, 2013). A network of brain areas rather than a single brain region seems to underlie synesthesia (Rouw et al. 2011) and MRI studies can show a clear distinction between regular associations (‘grass’ and ‘green’) and associations of synesthetes. Other neurological research studies show that an increased connectivity between brain regions underlying grapheme and color processing is reflected in the perceptual experience of colored graphemes in grapheme-color synesthetes (Brang et al., 2010; Ramachandran & Hubbard, 2001).

A recently published study by Colizoli et al. (2012) is the first known study using reading in color to train letter-color associations in non synesthetes. The results of this study indicate that it is possible for non synesthetes to acquire a subset of synesthetic behavioral traits through reading in

9 color. So why is it interesting to train synesthesia in non-synesthetes at all? The inducers in the grapheme-color subtype are linguistic and are learned since language is learned. It is very interesting to know whether it can be acquired via repeated exposure to letters in certain colors. Because the study of Colizoli et al. (2012) concerns a ‘reading’ study, interest was aroused to take the paradigm of this study to another level using participants with reading difficulties. There is no knowledge of a previous study testing the effects of learning letter-color associations in people with reading difficulties, like dyslexia. Perhaps a subset of difficulties experienced by dyslexics can be bypassed by training a different brain system involved in reading in color. Of course, dyslexics show a wide variety in reading difficulties, among other a reduced reading automaticity, a reduced mental flexibility (shifting visual attention) and greater attention interference (Kapoula et al. 2011). This latter is tested by Kapoula et al. (2010) using a flexible Stroop task, showing greater interference in dyslexics compared to non-dyslexics. This project will be a nice follow up study to both Kapoula et al. (2010) and Colizoli et al. (2012) because a combination of dyslexia and training letter-color associations by reading in color has not yet been made.

1.2 Dyslexia

Learning disabilities are one of the most common neurobehavioral disorders and dyslexia is one of the many disorders that falls within this group (Johannes et al. 1996). Dyslexia has a prevalence of 5-10% in all school-going children (Johannes et al., 1996; Shaywitz, 1998; Taroyan & Nicolson, 2009). The exact neurobiological background of dyslexia however, is still unknown. First there is a distinction between developmental versus acquired dyslexia after brain damage for instance. Different brain areas can be affected in people with reading difficulties or specifically, dyslexia. Most frequently mentioned are a left temporopartial hypoactivation (Guibert, de et al. 2011; Shaywitz and Shaywitz, 2008) and hyperactivation of the anterior insula during reading tasks (Maisog et al., 2008; Richlan et al., 2009). There seem to be two different routes that can be damaged in dyslexia, but it is mostly a combination where both are affected. The two routes are the visual semantic and the phonological one. Damage to the semantic route causes ‘surface dyslexia’ and damage to the phonological route causes ‘phonological’ or ‘deep dyslexia’. Another theory is the Magnocellular Hypothesis which describes that dyslexics have an impaired function of the visual magnocellular system which causes their reading impairment (Stein & Talcott, 1999). The magnocellular system is responsible for contrast and movement among other things and the parvocellular system is mainly sensitive to colors (Stein & Talcott, 1999). However, the magnocellular and the parvocellular system constantly interact with each other because they both are parts of a bigger network. Presumably, reading in color activates especially the parvocellular system, while the magnocellular is assumed to

10 be defective in dyslexia. It is possible that the magnocellular system can be bypassed by training the unimpaired parvocellular system. When the magnocellular system can be bypassed by reading in color, this means that in the end the parvocellular system can be used to take over some defective functions of the magnocellular system in dyslexics, namely reading comprehension and letter identification. When participating in this study causes dyslexics to acquire letter-color associations, the effects of these associations should be found in some of the tasks used in this research. When these effects are evidently present, hopefully some improvements can be seen, which means it is really possible for the parvocellular system to take over some deficits of the magnocellular system. Of course a wide range of individual differences has to be taken into consideration while studying dyslexics. Dyslexics in this study report a variety of difficulties while reading. Some notice especially their lack of concentration or focus makes it difficult to read. They report it is hard to keep track of where they are on a page and notice filling in some of the gaps using their imagination. For this reason, staying concentrated while reading takes a lot of time for the dyslexics. For some, this time consuming effect is a reason to avoid reading as much as possible.

1.3 Key questions and hypotheses

The general research question of this project is what the effects of training letter-color associations in dyslexics are on their reading abilities and processes compared to the effects on non-dyslexics. Specifically, do the participants show any improvements on reading comprehension after reading in color? Four tasks will be used in this research, 1) the Synesthetic Stroop task, 2) a reading speed task, 3) a visual-spatial working memory task, and 4) a lexical decision task. The visual-spatial working memory task is added in this research as a control task, since it is unrelated to the training (reading in color) itself. First hypothesis is that the participants show an increase in the Stroop effect after reading in color. This increase means that letter-color associations are appropriately acquired after reading in color. Second hypothesis is that reading speed increases, resulting in a shorter time they spend on the reading task after reading in color compared to before the reading. Next to an increased reading speed after reading in color, a big difference is expected between the baseline reading speed of dyslexics compared to non- dyslexics. Dyslexics are expected to read significantly slower compared to non-dyslexics. As regards to the lexical decision task, dyslexics are expected to have a disadvantage on reaction time and accuracy indicating non-words. Several studies have shown non-words or pseudo-words are difficult for dyslexics to read (Taroyan & Nicolson, 2009). Overall is hypothesized that the dyslexic group will show the biggest changes between testing sessions in all tasks, with the exception of the working memory task, because this task does not test reading or the

11 potential effect of letter-color associations. Mainly, hopefully an improvement in reading abilities is seen in the results and experienced by the participants themselves after reading in color.

When letter-color associations are successfully acquired participants should show a significant increase in the Stroop effect after reading in color compared to before reading. A Stroop effect in reaction times means that participants responded to incongruent trials significantly slower than congruent trials. Because the Stroop task is pretty simple, the participants are expected not to make many mistakes, resulting in small differences in accuracy and missed trials before and after reading. Predicted are great differences between dyslexics and non dyslexics, especially in Stroop reaction times and reading speed, but a within subjects design should show significant improvements in both groups after reading. Also, a third group participating in both testing sessions that will read books with just black text instead of colored books, will help to further rule out possible test-retest effects. Hopefully participants, especially diagnosed with dyslexia, report on questionnaires after the second testing session that reading in color actually improved some reading properties.

2. METHODOLOGY

2.1 Participants

This experiment was approved by the ethical committee of the Department of Psychology at the University of Amsterdam. Participants were informed that they could stop participating at any time without having to give a reason and gave written informed consent before participating in the research. Involvement of all participants was completely voluntary and they were selected based on their motivation to read. The participants had to be motivated to read voluntarily for this study, since they would receive a compensation of €10,- for each testing session of one hour. The time the participants spend reading at home could not be compensated due to the fact that the exact amount of time the participants spend reading is not controllable. For that reason people who love to read and do read on a regular base are recruited. This way, the books they had to read for this research would only replace the books they would normally read in their free time. A total of 27 participants (M = 23.4 years, SD = 4.5) (see Table 1) was recruited for this research using social media, email and flyers around the University of Amsterdam. Participants were excluded when they had a history of brain injuries or other neurological problems (i.e. ADD), have a bad vision or are colorblind. Colorblindness was tested with the Ishihara Test for Color Blindness (Ishihara, 1917). Participants also were excluded if they experience any symptoms of synesthesia, especially the grapheme-color subtype of synesthesia. Participants were divided in three experimental groups, the first group consisting of dyslexics (N = 9, M = 23.6 years, SD = 6.4) and two control groups consisting of

non-12 dyslexics (N = 18). The control groups were composed of participants comparable to the dyslexics in age, education and gender and controls were randomly assigned to one of the control groups. Every group participated in two testing sessions with an interval of reading in between the two sessions. The first control group (N = 10, M =24 years, SD = 3.3) would read in color just like the first (dyslexic) group, but the second control group (N = 8, M = 23.5 years, SD = 4.5) would read about the same amount in black text. Dyslexics were asked about the timing of their diagnosis and doctor or psychologist accountable for it. Most dyslexics were diagnosed in high school (M = 15 years, SD = 2.12) by a psychologist.

Table 1. Participants. The average age and female to male ratio per group. Group 1 consists of the dyslexics

and group 2 and 3 are the control groups consisting of non-dyslexics. Group 2 followed the exact same training of reading in color as group 1. Group 3 followed a training of reading in black instead of in color.

Group N Age F:M M SD 1 9 23.56 6.42 7:2 2 10 24.2 3.16 6:4 3 8 22.75 3.41 7:1 Total 27 23.56 4.43 2.2 General procedure

The experiment of this research consisted of two testing sessions of one hour with an interval of 3-8 weeks between the two sessions. Both testing sessions occurred in a controlled testing room at the University of Amsterdam and computer tasks were executed on the same computer for all participants. The stimuli of the different tasks were presented using Presentation, version 17.0 (Neurobehavioral Systems, 2003 – 2010). Responses were made using the keyboard or a computer mouse in case of the chessboard task. The first testing session consisted of a total of four different computer tasks and one or two questionnaires, depending on the group number. During the first testing session, all participants received a synesthetic consistency test and the dyslexics in group 1 received an extra questionnaire about their reading experience in general. All questionnaires and consistency tests were in Dutch. Between the two testing sessions, participants were asked to read as much as possible, at least something every day. It was very important to keep track of the exact amount of words that was read by each participant to be able to test the effect of the amount of

13 words they read on the results of the tasks. In total, nine participants completed one book and twelve participants completed two books. The second testing session consisted of another two questionnaires and the same four computer tasks as in the first testing session. The second version of the consistency test is given in the second testing session and all of the participants received a modified questionnaire about their experience in reading in color (or black) during the research. Statistical analyses were executed using the Statistical Package for Social Sciences (SPSS) for Windows, version 20.0 (IBM, 2011).

2.3 Letter-color preferences

Before participating in the experiments, participants were asked for their letter-color preferences with a 5-point Likert scale questionnaire presenting each letter used in this study (‘e’, ‘n’, ‘a’, ‘r’) in the four colors used (red, orange, green or blue). A score of 1 or 2 indicated a non-preferred letter-color combination, 4 or 5 indicated a preferred letter-letter-color combination and a score of 3 indicated a neutral preference. All participants were given their non-preferred letter-color combinations during the synesthetic Stroop task as well as in their books. The reason for reading in non-preferred combinations is to enhance the potential effects as much as possible. It was in fact found that participants who got their non-preferred pairs showed a larger post-training Stroop effect (Colizoli et al., 2014; Colizoli et al., 2012). Because both dyslexics and non-dyslexics received their non-preferred combinations, no bias of preference is expected in the different groups.

2.4 Reading materials

Participants were able to choose a book from a customized list of books given by the publisher Nijgh & Van Ditmar, Amsterdam. All books were in Dutch and were printed and bound at the University of Amsterdam. Books were colored based on the letter- color preferences of the participants using customized Macros in Microsoft Word. The first book was handed to the participants after the first testing session. When almost completing their first book, participants were mailed their second book, making sure there was no large interval between reading the books.

2.5 Reading experience dyslexics

During the first testing session, dyslexics were given an extra questionnaire to describe their experiences with reading and having dyslexia. A five-point Likert scale, where ‘1’ referred to ‘I strongly disagree’ and ‘5’ referred to ‘I strongly agree’ was used to indicate whether participants

14 agreed to the following 13 statements: 1) I enjoy reading (in general). 2) I read slower than the average person. 3) I struggle to hold my attention while reading. 4) I read more often than the average person. 5) When I read, I am easily distracted. 6) It costs me a lot of effort to concentrate while reading. 7) I read quicker than the average person. 8) I have no trouble holding my attention while reading. 9) I read less often than the average person. 10) I am not easily distracted while reading. 11) I have no trouble concentrating while reading. 12) My dyslexia causes me to dislike reading more. 13) My dyslexia causes me to need more time to read a book. Also, they had room to give a written answer to the openly asked question 14) My dyslexia limits me while reading, yes/no. If yes, describe the extent to which your reading is limited by dyslexia. In the second testing session, the dyslexics were also able to openly report how they experienced reading in color related to their dyslexia.

2.6 Synesthetic consistency tests

During both first and second testing session, participants were handed a synesthetic consistency test. The first consistency test consisted of an alphabetical set of letters (A-Z) and a chronological set of numbers (0-9) and days of the week (‘Monday’- ‘Sunday’). At the top of the test was the question ‘If each letter, number or day was to have a color, what would it be?’. Participants were asked to describe a color to each item, with every color possible. During the second testing session, participants were given the second consistency test asking the same question. This time however, letters, numbers and days were not in alphabetical or chronological order. Participants without synesthesia were expected to randomly assign colors to the letters, numbers and days, without being consistent between the first and the second consistency test.

2.7 Synesthetic Stroop task

Before the Stroop task, participants were given a training task on the response mappings to learn which button corresponded with which color. Participants were randomly assigned to two button conditions (i.e. button condition 1: ‘enar’, button condition 2 ‘rane’). This button condition reflects the order of the colored stickers on the keypad. The keys used in this training are the N, M, < and > and red, orange, green and blue colored stickers were put on the buttons that corresponded to these colors to help learning the right combinations. For example, when the non-preferred color to the letter ‘r’ is red, for the letter ‘a’ blue, for the letter ‘n’ green and for the letter ‘e’ orange and this participant is randomly assigned to button condition 2, the order of the colored stickers on the keys (NM<>) would be red-blue-green-orange. The different button conditions control for the effect of

15 difficulties in using the little finger compared to the index finger, hence participants had to use four fingers on one hand. The task started with a colored block presented on a blank screen and participants were asked to indicate the color of the block (red, orange, green or blue). Participants were asked to react as accurate and fast as possible and received feedback after each trial. When participants did not need to glance at their fingers anymore during the task, they successfully acquired the color-button combinations and were able to continue with the Synesthetic Stroop task. Stimulus material of the Stroop task consisted of four different letters (‘e’, ‘n’, ‘a’, ‘r’) presented one at a time in one of the four colors (red, orange, green or blue). One of the letters was centrally presented in black before it changed into one of the four colors (see Figure 1). First participants look at a blank screen for 500 milliseconds, after which a fixation cross appears for 1500 milliseconds. After a letter appeared in black for 200 milliseconds, it changed into its color, until the participant corresponded with a button press. When the participant responded with a color, the next letter was presented without giving feedback. Reaction times, accuracy and missed trials were reported during the Synesthetic Stroop task.

Figure 1. Synesthetic Stroop task. After a blank screen for 500 milliseconds and a fixation cross to focus on the

center of the screen for 1500 milliseconds, one of the four letters (e, n, a, r) is shown in black for 200 milliseconds and turns into one of the four colors (red, orange, green or blue). Participants were asked to response as fast and accurate as possible the moment the letter changes color. The next trial starts after the response of the participant. Before this task, participants learned which letter corresponded with what button on the keypad.

2.8 Reading Speed

Participants were asked to read 10 different chunks of text (M=116.4 words, SD=14.8) all obtained from news websites. The participants were asked to read as fast as they would normally do to obtain their average reading speed as accurate as possible. After reading one text they had to press a button to continue and the next text would appear. During the second testing session, participants read another 10 chunks of different texts (M = 115.3 words, SD = 10.4) to compare average reading

e

e

+

16 speed with the first reading session. Chunks of text were randomized per participant within each testing session.

2.9 Chessboard

To test for differences between participants and groups that are not related to reading, a working memory ‘Chessboard’ test is used (see Figure 2). A 4x4 chessboard like figure is shown with green and blue boxes. One trial consists of a series of stimuli appearing one by one in different boxes. Participants are asked to remember the order in which the stimuli appeared by first clicking on the green boxes and then on the blue boxes both in the right order. After a set of three correct trials, one stimulus was added to raise the difficulty level. After a set of three incorrect trials, the difficulty level was again decreased by taking down one stimulus.

Figure 2. Chessboard task. Participants were instructed to click on the right order, first for all the green boxes,

second for all the blue boxes. Shown above is an example of a correct trial.

2.10 Lexical Decision

Last, participants performed the lexical decision task (see Figure 3). A fixation cross is shown for 1000 milliseconds to focus on the center of a blank screen. After a prime series of characters of 40 milliseconds the target would appear on the screen for 1000 milliseconds. Participants are asked to define the target as a ‘word’ or as a ‘non-word’ as fast as possible. If participants had not yet made their choice after 1000 milliseconds, ‘Too late!’ would appear on the screen before continuing to the next trial. For 180 trials, reaction times and missed trials are reported for each participant.

17 Figure 3. Lexical decision task. After a fixation cross and a series of characters to focus attention to the center

of the screen, participants had to indicate the target as a ‘word’ or a ‘non-word’. When participants did not respond within 1000 milliseconds, ‘Too Late!’ would appear and the next trial would begin.

2.11 Reading experience group 1 and 2

At the beginning of the second testing session, participants were given a questionnaire targeting their reading experience. For the dyslexics and first control group questions regarded reading in color and they had to assign scores to statements on a 5-point Likert scale where ‘1’ referred to ‘I strongly disagree’ and ‘5’ referred to ‘I strongly agree’. The following statements were used in this reading experience questionnaire: 1) The colored text was esthetically appealing (i.e. ‘pretty’). 2) I read less than the average person. 3) I like the color orange. 4) I enjoy reading (in general). 5) When I see certain letters (e, n, a, r) in black text, I see them in color. 6) I tend to read books from the same genre. 7) The colored text was ‘ugly’. 8) It felt as if I was reading faster in color (at the end of the book). 9) When I think of certain letters (e, n, a, r), I experience them in color (in imagination). 10) I read more than the average person. 11) I like the color green. 12) I enjoyed reading in color. 13) It felt as if I was reading more slow in color (at the end of the book). 14) When I think of certain letters (e, n, a, r), I see them in color. 15) The colored text was distracting. 16) I was more motivated to read this book compared to reading a book with normal black text. 17) The colored text became less distracting in time. 18) When I see or think about letters, I do not experience any colors. 19) I like the color red. 20) I enjoyed the contents of the book. 21) I tend to read books from different genres. 22) When I see certain letters in black (e, n, a, r), I experience them (imaginative) in color. 23) I was less motivated to read this book compared to books with normal black text. 24) The colored text became more distracting in time. 25) I like the color blue. 26) When I see certain letters in black, I do not see or experience any (imaginative) colors, but I do have an automatic association with color. On extra closed question was to be answered by choosing one of the following statements that fitted best to the current experience of the participant: a) When I see certain letters in black (e, n, a, r), I see them in color. b) When I see certain letters (e, n, a, r) in black, I experience them (imaginative) in color. c) When I think of certain letters (e, n, a, r), I experience them (imaginative) in color. d) When I think of certain letters (e, n, a, r), I see them in color. e) When I see or think about certain letters, I do not

+ #$%&#$% drans

1000ms 40ms 1000ms

18 experience any color. f) When I see certain letters in black, I do not see or experience (imaginative) any colors, but I do have an automatic association with color. Participants were also able to give a written answer to the question ‘Have you noticed any changes in behavior or experience since you started reading in color?’

2.12 Reading experience group 3

As for group 3 that did not perform the reading in color, a different questionnaire about their reading experience was modified. They also scored statements on a 5-points Likert scale were ‘1’ referred to ‘I strongly disagree’ and ‘5’ referred to ‘I strongly agree’. The following statements were used in the questionnaire: 1) The books I read were very interesting. 2) I read less than the average person. 3) Without participating in this study, I would never have chosen the same books to read. 4) I enjoy reading (in general). 5) When I see certain black letters (e, n, a, r), I see them in color. 6) I tend to read books from the same genre. 7) I thought the books were difficult. 8) It felt like I was reading faster towards the end of the books. 9) When I think of certain letters (e, n, a, r), I experience them in color (imaginative). 10) I read less than the average person. 11) Participating in this study, I read more than I usual do. 12) I liked reading the books. 13) It felt like I was reading slower towards the end of the book. 14) When I think of certain letters (e, n, a, r), I see them in color. 15) I was very motivated to read the books. 16) I usually only read when I have to (study for instance). 17) It bothered me that the books were printed. 18) When I see or think of certain letters, I do not experience colors. 19) I usually only read when I have spare time. 20) I enjoyed the content of the books. 21) I tend to read books from different genres. 22) When I see certain black letters (e, n, a, r), I experience them in color (imaginative). 23) The books were not difficult to read. 24) In daily life, I make time to read. 25) How the books were printed and bound, did not bother me. 26) When I see certain letters in black texts, I do not experience or see (imaginative) any colors, but I do have an automatic association with color. They also had to choose one of the following statements about possible letter-color associations: 27)a) When I see certain black letters (e, n, a, r), I see them in color. b) When I see certain black letters (e, n, a, r), I experience them in color (imaginative). c) When I think of certain letters (e, n, a, r), I experience them in color (imaginative). d) When I think of certain letters (e, n, a, r), I see them in color. e) When I see or think of certain letters, I do not experience any colors. f) When I see certain black letters, I do not see or experience any colors (imaginative), but I do have an automatic association with colors. Participants were able to openly explain their answer and describe their subjective experience with reading answering the last question: 27) Have you noticed any changes in behavior or experience since you started reading for this study?

19

3. RESULTS

A total of 21 participants completed two testing sessions. The results of the computer tasks are based on this number of participants, resulting in group 1 consisting of 8 dyslexics, group 2 consisting of 8 participants and group 3 consisting of 5 participants. Six participants completed the first testing session, but did not complete the reading and/or the second testing session for varying reasons. A couple of reasons are examined in the discussion section to take into account for future research. One participant appeared to have difficulties in distinguishing colors when tested with the Ishihara test for colorblindness. However, this participant could distinguish the colors used in the books and the Stroop tasks, therefore the data of this participant is still included in the set of data. The number of books and the amount of words read by the participants is shown in Table 2.

3.1 Reading Speed

During both testing sessions, the average reading speed of the participants is recorded using 10 different chunks of text, randomized within each session. Table 2 shows the average reading speed of participants during the first (‘Pre Reading speed’) and the second (‘Post Reading speed’) testing session. In Table 3, means and standard deviations of reading speed for the groups is shown.

Table 2. Amount of reading and reading speed. An overview of the amount of words the participants read in

color or black between the first and second testing session and their reading speed during the two testing sessions. ‘Pre Reading speed’ refers to the average reading speed in words per second during the first testing session and ‘Post Reading speed’ refers to the average reading speed in words per second during the second testing session. Group 1 consists of the dyslexics who read in color, group 2 consists of the non-dyslexics who read in color and group 3 consists of the non-dyslexics who read in black.

Participant (N = 21)

Group #Books read Word Count Pre Reading speed (Words/s) M

Post Reading speed (Words/s) M 1 1 1 23969 .93 1.1 2 1 1 39141 2.64 3.47 4 2 2 114788 4.87 1.08 5 2 2 96535 3.55 3.93 7 2 2 177798 4.65 4.79 8 1 2 96535 3.28 1.0 9 2 2 128475 3.27 3.8

20 10 2 2 100684 4.6 5.37 11 1 2 97768 4.93 5.61 13 2 2 125322 4.7 6.48 14 2 2 53954 2.82 3.8 16 3 2 96019 6.06 6.94 18 3 1 78545 5.93 6.75 20 2 2 64260 4.89 5.06 21 1 1 84597 3,93 4.56 22 1 1 13449 5,29 6.57 23 3 1 83398 3.97 4.62 24 3 1 43437 5.85 5.19 25 3 2 79202 5.99 6.18 26 1 1 51836 5.66 9.91 27 1 1 1082 4.18 4.95 Mean 1.57 78609.24 4.38 4.82 St. dev. .49 41977.7 1.31 2.12

Table 3. Amount of reading and reading speed for each group. Averages and standard deviations of the

amount of words the groups read and their reading speed during the first testing session (‘Pre Reading speed’) and the second testing session (‘Post Reading speed’). Group 1 consists of the dyslexic participants and group 2 and 3 of non-dyslexic participants.

Group Word count Pre Reading speed (Words/s)

Post Reading speed (Words/s) M SD M SD M SD 1 (N = 8) 51047.13 38103.84 3.85 1.56 4.65 2.92 2 (N = 8) 107727 39015.83 4.17 .82 4.29 1.59 3 (N = 5) 76120.2 19573.56 5.56 .89 5.94 1.0 Total (N = 21) 78609.24 41977.7 4.38 1.31 4.82 2.12

An increasing trend can be seen in reading speed between the first and the second testing session. All three groups appear to have an increased reading speed in the second testing session compared to the first testing session (see Table 3 above and Figure 4 below).

21 Figure 4. Reading speed. The mean reading speed in words per second for each group during the first (Pre) and

the second (Post) testing session. Group 1 consists of the dyslexic participants, group 2 and 3 are the control groups consisting of non-dyslexics. Error bars indicate the standard error of the mean.

A repeated measures ANOVA is executed to test for differences in average reading speed between the first and second testing session with reading speed as the within-subjects factor and group as the between-subjects factor. The assumption of sphericity is not violated, as there are two conditions. No overall significant difference is found in reading speed between the first and the second testing session (F(1,18) = 1.55, p = .229, p >.05). Likewise, no significant main effect of group is found (F(2) = 1.84, p = .187, p > .05). Another repeated measures ANOVA is executed with the amount of words the participants read as a between-subjects factor. No significant effect of the amount of words on reading speed is found (F(1,19) = 2.04, p = .508, p >.05).

3.2 Chessboard

At the end of the Chessboard working memory task (see Figure 2), participants were given a score which reflected their overall performance during the task. The score had a range between 300 and 370 points. Figure 5 shows the mean scores within experimental groups for the first and the second testing session. 0 1 2 3 4 5 6 7 Pre Post M e an r e ad in g sp e e d ( wo rd s/s)

Readingspeed

Group1 Group2 Group3

22 Figure 5. Mean chessboard scores. Mean chessboard scores for the three experimental groups during in the

first (Pre) and the second (Post) testing session. Group 1 consists of the dyslexic participants and group 2 and 3 consist of the non-dyslexics. Error bars indicate the standard error of the mean.

There appears to be a trend difference between the first two groups and group 3 as the mean score for group 1 and 2 is increased in the second testing session compared to the first testing session, the mean score for group 3 however, is decreased in the second testing session compared to the first testing session. A repeated measures ANOVA is executed to measure if there is a significant difference between scores in the two testing sessions. The assumption of sphericity is not violated as there are just two conditions; pre- and post-reading chessboard scores. No overall significant differences in chessboard test scores are found between testing sessions (F(1,16) = 1,85, p = .193, p > .05). Likewise, there is no significant main effect of group (F(2) = 1.84, p = .933, p > .05).

3.3 Lexical Decision

In the lexical decision task, participants had to indicate the target as a ‘word’ or a ‘non-word’ within 1000 milliseconds (see Figure 3). A repeated measures ANOVA is executed to measure differences in reaction times between groups and between testing sessions. An overall significant effect is found for word category (F(1,18) = 81.24, p = .00, p < .05). Participants appeared to be faster indicating words compared to non-words (see Figure 6). The dyslexics (group 1) appeared to be slower

310 320 330 340 350 360 Pre Post M e an c h e ssbo ar d sco re s

Chessboard

Group1 Group2 Group3

23 indicating both words and non-words compared to control groups 2 and 3, but no significant main effect of group is found (F(2) = .67, p = .522, p > .05). There is a significant interaction effect between word category and testing session (F(1,18) = 4.48, p = .048, p < .05).

Figure 6. Lexical decision, words versus non-words. Mean reaction times (RT) of the three groups are shown

for categorizing the targets as word or non-word. Group 1 consists of the dyslexics, group 2 and 3 are the control groups consisting of the non-dyslexics. Participants were faster indicating words compared to indicating non-words (F(1,18) = 81.24, p = .00, p < .05). Error bars indicate the standard error of the mean.

Participants did not appear to response different to both words and non-words in the second testing session compared to the first testing session. No significant difference between testing sessions is found F(1,18) = 1,21, p = .286, p > .05.

3.4 Stroop

For each participant, reaction times, accuracy and missed trials are recorded during the Stroop task (see Figure 1) in the first and second testing session. Figure 7 shows mean reaction times for congruent and incongruent trials for each group during the first and the second testing session.

500 600 700 Words Nonwords M e an R T ( m s) Word category

Lexical decision

Group1 Group2 Group3

*

24 a)

b)

Figure 7. RT Congruent and incongruent trials Stroop. Reaction times (RT) of congruent (a) and incongruent (b)

trials before (Pre) and after (Post) training. Group 1 is the dyslexic group, group 2 and 3 are the control groups consisting of non-dyslexics. Error bars indicate the standard error of the mean.

0 200 400 600 800 1000 1200 Pre Post M e an R T ( m s)

Congruent Stroop trials

Group1 Group2 Group3 0 200 400 600 800 1000 1200 Pre Post M e an R T ( m s)

Incongruent Stroop trials

Group1 Group2 Group3

25 No significant difference in reaction times between congruent and incongruent trials is found (F(1,18) = 0, p = .995, p > .05), which means participants did not react significantly different between congruent and incongruent trials. Likewise, no main effect of group is found on congruency (F(2,18) = .897, p = .425, p > .05). There appears to be a downwards trend in reaction time after the first testing session in all three groups though (see figure 8).

a) b)

500 600 700 800 900 1000 1100 Pre Post M e an R T ( m s)

Reaction times Stroop

Group 1

Congruent Incongruent 500 600 700 800 900 1000 1100 Pre Post M e an R T ( m s)

Reaction times Stroop

Group 2

Congruent Incongruent

26 c)

Figure 8. Reaction times Stroop. Reaction times (RT) in milliseconds (ms) for congruent and incongruent trials

of the Stroop task for group 1 (a), 2 (b) and 3 (c) during the first (Pre) and the second (Post) testing session. Recall that group 1 consists of the dyslexic group with the reading in color training, group 2 of the non-dyslexics with the reading in color training, group 3 of the non-dyslexics with the reading in black training. Error bars indicate the standard error of the mean.

All groups react faster on congruent trials compared to incongruent trials in testing session 2 (see figure 8). Merely group 1 reacts slower to congruent trials compared to incongruent trials in testing session 1 (figure 8a). All groups show a decrease in reaction time for both congruent and incongruent trials after the first testing session (figure 8a-c).

Next to reaction time, accuracy of each trial is reported during the Stroop task. Figure 9 shows scored accuracy for congruent and incongruent trials of the Stroop task and Table 5 gives an overview of mean scores of accuracy for each group.

500 600 700 800 900 1000 1100 Pre Post M e an R T ( m s)

Reaction times Stroop

Group 3

Congruent Incongruent

27 a)

b)

Figure 9. Accuracy congruent and incongruent Stroop trials. An accuracy of 1,0 stands for 100% correctly

responded trials. For each group, accuracy for congruent (a) and incongruent (b) trials, pre and post reading are shown. Group 1: dyslexics with reading in color training. Group 2: non-dyslexics with reading in color training. Group 3: non-dyslexics with reading in black training. Error bars indicate the standard error of the mean.

Table 4. Accuracy Stroop. Accuracy of responses in congruent and incongruent trials during the first and

second testing session. Numbers are means and standard deviations of the three experimental groups. Group 1 consists the dyslexic participants, group 2 and 3 are the control groups with the non-dyslexic participants.

Group Accuracy congruent trials (%) Accuracy incongruent trials (%)

Pre reading Post reading Pre reading Post reading

M SD M SD M SD M SD 0,84 0,86 0,88 0,9 0,92 0,94 0,96 0,98 Pre Post A cc u rac y

Accuracy Incongruent Stroop trials

Group1 Group2 Group3 0,84 0,86 0,88 0,9 0,92 0,94 0,96 0,98 Pre Post A cc u rac y

Accuracy Congruent Stroop trials

Group 1 Group 2 Group 3

28

1 (N = 8) 89 .05 89 .04 87 .07 89 .04

2 (N = 8) 92 .05 93 .04 91 .07 95 .04

3 (N = 5) 96 .02 94 .02 96 .03 95 .04

Total (N = 21) 92 .05 92 .04 91 .07 93 .04

No significant difference in accuracy is found between congruent and incongruent trials in both testing sessions (F(1,18) = .068, p = .797, p > .05), which means participants were equally accurate reacting to incongruent trials as to congruent trials. There is a significant main effect of group (F(2,18) = 6.24, p = .009, p < .05). This main effect however, is not dependent of congruency or testing session (F(1,18) = 2.65, p = .121, p > .05). Figure 10 shows the overall accuracy, including both congruent and incongruent trials, for each group during the first and the second testing session. Group 1 and 2 appear to have increased in accuracy in the second testing session compared to the first testing session, group 3 however shows a decreased accuracy. Group 1 is less accurate compared to group 2 and 3 in both testing sessions, as well as group 2 is less accurate compared to group 3 in both testing sessions.

Figure 10. Overall accuracy Stroop. The overall accuracy in Stroop responses are shown of the three groups

during the first (Pre) and the second testing session (Post). An accuracy of 1 stands for 100% correctly

answered trials. The overall accuracy for each session includes both congruent and incongruent trials. Group 1 consists of dyslexic participants, group 2 and 3 of non-dyslexic participants. Error bars indicate the standard error of the mean.

0,84 0,86 0,88 0,9 0,92 0,94 0,96 0,98 Pre Post A cc u rac y

Overall Accuracy Stroop

Group1 Group2 Group3

29 The Stroop effect reflects the difference between incongruent and congruent trials. Table 6 gives an overview of the Stroop effects for each participant. Figure 8 already showed the differences in reaction time between congruent and incongruent trials (the Stroop effect) in both testing sessions for each group.

Table 5. The Stroop effect for each participant. The Stroop effect reflects the difference in reaction time (in

milliseconds) between incongruent and congruent trials (RT incongruent – RT congruent). For each participant, the Stroop effect during the first testing session (‘Pre-reading’) and the second testing session (‘Post-reading’) is shown. Participant 8 appears to be an outlier in Stroop effect data and is therefore removed from further Stroop analysis.

Participant (N = 21)

Group Word count Stroop effect Pre - reading Stroop effect Post - reading 1 1 23969 37,94 46,86 2 1 39141 16,74 10,93 4 2 114788 99,17 27,45 5 2 96535 89,49 15,39 7 2 177798 41,50 -23,40 8 1 96535 -872,36 -34,00 9 2 128475 -9,57 3,56 10 2 100684 -12,63 -4,67 11 1 97768 -8,81 19,79 13 2 125322 -15,88 -5,51 14 2 53954 -17,12 -18,21 16 3 96019 85,08 25,47 18 3 78545 -15,00 23,00 20 2 64260 40,86 35,70 21 1 84597 -19,11 80,97 22 1 13449 -2,34 30,13 23 3 83398 -26,60 78,48 24 3 43437 9,78 -55,05 25 3 79202 39,21 60,22 26 1 51836 66,36 42,05 27 1 1082 34,64 -47,45

30 No significant differences are found in Stroop effect for the participants between the first and the second testing session (F(1,17) = .035, p = .853, p > .05) and no main effect of group is found (F(2,17) = .138, p = .872, p > .05). See Table 7 for an overview of the means and standard deviations of the Stroop effect for each group.

Table 6. The Stroop effect for each group. Means and standard deviations of the Stroop effect in reaction time

for each group are shown. Stroop data of one participant is excluded, hence a total N of 20. Group 1 consists of the dyslexics who read in color, group 2 consists of the non-dyslexics who read in color and group 3 consists of the non-dyslexics who read in black.

Group Stroop effect Pre Stroop effect Post

M SD M SD 1 (N = 7) 17.92 30.34 18.66 42.36 2 (N = 8) 26.98 48.12 3.79 21.02 3 (N = 5) 21.69 39.87 14.84 37.36 Total (N = 20) 21.69 39.87 14.84 37.36

Introducing the amount of words as a covariate in the repeated measures ANOVA did not indicate a significant difference in Stroop effect between the participants that was dependent on the amount of words they read between the two testing sessions (F(1,16) = .40, p = .535, p > .05).

3.5 Reading experience dyslexics

During the first testing session, dyslexics were given an extra questionnaire to describe their experiences with reading having dyslexia. The participants scored the statements on a five-point Likert scale, where ‘1’ referred to ‘I strongly disagree’ and ‘5’ referred to ‘I strongly agree’ as follows: 1) I enjoy reading (in general).: M = 4.14, SD = 1.46. 2) I read slower than the average person.: M = 3,

SD = 1.41. 3) I struggle to hold my attention while reading.: M = 2.57, SD = 1.51. 4) I read more often

than the average person.: M = 2.86, SD = 1.35. 5) When I read, I am easily distracted.: M = 2.43, SD = 1.27. 6) It costs me a lot of effort to concentrate while reading.: M = 2.71, SD = 1.38. 7) I read quicker than the average person.: M = 2.43, SD = 1.27. 8) I have no trouble holding my attention while reading.: M = 3.14, SD = 1.21. 9) I read less often than the average person.: M = 2.71, SD = 1.50. 10) I am not easily distracted while reading.: M = 3.14, SD = 1.57. 11) I have no trouble concentrating while reading.: M = 3.57, SD = 1.27. 12) My dyslexia causes me to dislike reading more.: M = 1.86, SD

31 = 1.21. 13) My dyslexia causes me to need more time to read a book.: M = 2.86, SD = 1.86. To the question whether dyslexia is limiting the participants during their reading all but two participants explained that being dyslexic is limiting them one way or another. Most of the participants still enjoy reading a lot in general. Biggest obstacles for the dyslexics are a slow reading speed and the fact that reading costs a lot of effort. For these reasons, some of the dyslexics read less than they would have liked because it takes more time. Especially when they have to read a lot for their study, they tend to read less for fun. The two participants who indicated that their dyslexia is not limiting them one way or another read a lot in their spare time and they feel that maybe this way they are compensating possible reading difficulties by practice. During the second testing session, the dyslexics were asked to openly report their experience with reading in color related to dyslexia. Some of the dyslexic participants did not notice any changes after reading in color, especially the dyslexics without major reading difficulties. One dyslexic participant who seemed to be most severely affected by dyslexia did find the colored letters very distracting. During reading in color for a while however, the colors became less distracting and he did not notice any differences with reading in black anymore. Some of the dyslexics even reported that the use of colors provided some structure in the book, which made it easier to read. All these subjective reports can be taken into account for future research using reading in color as a training for dyslexics.

3.6 Reading experience group 1 and 2

Participants from group 1 and 2 answered questions about their experience with reading in color giving scores from ‘1’ (‘I strongly disagree’) to ‘5’ (‘I strongly agree’) as follows: 1) The colored text was esthetically appealing (i.e. ‘pretty’): M = 2.94, SD = .93. 2) I read less than the average person.: M = 2.13, SD = 1.09. 3) I like the color orange.: M = 3.0, SD = .97 4) I enjoy reading (in general).: M = 4.5,

SD = .82. 5) When I see certain letters (e, n, a, r) in black text, I see them in color.: M = 1.69, SD = .95.

6) I tend to read books from the same genre.: M = 3.5, SD = 1.15. 7) The colored text was ‘ugly’.: M = 2.38, SD = .81 8) It felt as if I was reading faster in color (at the end of the book).: M = 3.31, SD = 1.30. 9) When I think of certain letters (e, n, a, r), I experience them in color (in imagination).: M = 1.94, SD = 1.12. 10) I read more than the average person.: M = 3.56, SD = .96. 11) I like the color green.: M = 3.75, SD = .86. 12) I enjoyed reading in color.: M = 3.56, SD = 1.09. 13) It felt as if I was reading more slow in color towards the end of the book.: M = 2.44, SD = 1.09. 14) When I think of certain letters (e, n, a, r), I see them in color.: M = 2.07, SD = 1.22. 15) The colored text was distracting.: M = 3.07, SD = .96. 16) I was more motivated to read this book compared to reading a book with normal black text.:

M = 2.73, SD = 1.44. 17) The colored text became less distracting over time.: M = 4.33, SD = .72. 18)

32 color red.: M = 3.6, SD = .91. 20) I enjoyed the contents of the book.: M = 3.67, SD = 1.23. 21) I tend to read books from different genres.: M = 3.0, SD = 1.20. 22) When I see certain letters in black (e, n, a, r), I experience them (imaginative) in color.: M = 1.73, SD = .96. 23) I was less motivated to read this book compared to books with normal black text.: M = 2.6, SD = 1.59. 24) The colored text became more distracting in time.: M = 2.33, SD = 1.50. 25) I like the color blue.: M = 4.13, SD = .74. 26) When I see certain letters in black, I do not see or experience any (imaginative) colors, but I do have an automatic association with color.: M = 2.8, SD = 1.3. Choosing one statement in the last question, most of the participants chose e) ‘When I see or think of certain letters, I do not experience any colors’ or f) ‘When I see certain black letters, I do not see or experience any colors (imaginative), but I do have an automatic association with colors’. Table 8 gives an overview of the means and standard deviations per group for all the reading experience questions. Note that group 3 received a questionnaire different from the one participants from group 1 and 2 received.

Table 7. Reading experience questionnaire. Means and standard deviations of scores given on the reading

experience questionnaire by dyslexics (group 1) and non-dyslexics (group 2 and 3). Note that the questionnaire completed by group 1 and 2 are the same, asking about reading in color, but different from group 3.

Question number Group 1 (N = 8) M Group 1 SD Group 2 (N = 8) M Group 2 SD Group 3 (N = 5) M Group 3 SD 1 3 .93 2.88 .99 3.8 .98 2 2.63 1.30 1.63 .52 2 .89 3 3.25 .89 2.75 1.04 3.6 1.02 4 4.25 1.04 4.75 .46 5 0 5 1.88 1.13 1.5 .76 1.4 .8 6 3.38 1.19 3.63 1.19 3.8 .98 7 2.38 .52 2.38 1.06 1.4 .49 8 3.38 1.30 3.25 1.39 3.6 .8 9 2 1.20 1.88 1.13 2.4 1.50 10 3.13 1.13 4 .53 3.6 .8 11 3.75 .71 3.75 1.04 2.8 .4 12 3.5 1.41 3.63 .74 4 1.1 13 2.5 .53 2.38 1.51 2.4 .8 14 2.13 1.36 2 1.15 2.2 1.17

33 15 3 .93 3.14 1.07 3.8 .4 16 2.25 1.39 3.29 1.38 1.4 .49 17 4.38 .74 4.29 .76 2.2 1.17 18 3.75 1.75 3.57 1.27 3.8 1.47 19 3.38 .92 3.86 .90 2.8 1.17 20 3.63 1.51 3.71 .95 4 1.1 21 3.13 1.13 2.86 1.35 3.4 1.02 22 1.63 1.06 1.86 .90 2.2 1.17 23 2.88 1.81 2.29 1.38 4.2 .4 24 2.13 1.36 2.57 1.72 3.2 .75 25 4 .76 4.29 .76 3.8 1.17 26 2.63 1.41 3 1.29 2 1.1

3.7 Reading experience group 3

Participants in group 3 who read books in black answered questions about their reading experience on a 5-points Likert scale as follows (shown in Table 8): 1) The books I read were very interesting.: M = 3.8, SD = .98. 2) I read less than the average person. M = 2, SD = .89. 3) Without participating in this study, I would never have chosen the same books to read. M = 3.6, SD = 1.02. 4) I enjoy reading (in general).: M = 5. 5) When I see certain black letters (e, n, a, r), I see them in color.: M = 1.4, SD = .8. 6) I tend to read books from the same genre. M = 3.8, SD = .98. 7) I thought the books were difficult.: M = 1.4, SD = .49. 8) It felt like I was reading faster towards the end of the books.: M = 3.6, SD = .8. 9) When I think of certain letters (e, n, a, r), I experience them in color (imaginative). M = 2.4, SD = 1.50. 10) I read less than the average person.: M = 3.6, SD = .8. 11) Participating in this study, I read more than I usual do.: M = 2.8, SD = .4. 12) I liked reading the books.: M = 4, SD = 1.1. 13) It felt like I was reading slower towards the end of the book.: M = 2.4, SD = .8. 14) When I think of certain letters (e, n, a, r), I see them in color.: M = 2.2, SD = 1.17. 15) I was very motivated to read the books.: M = 3.8,

SD = .4. 16) I usually only read when I have to (to study for instance).: M = 1.4, SD = .49. 17) It

bothered me that the books were printed.: M = 2.2, SD = 1.17. 18) When I see or think of certain letters, I do not experience colors.: M = 3.8, SD = 1.47. 19) I usually only read when I have spare time.: M = 2.8, SD = 1.17. 20) I enjoyed the content of the books.: M = 4, SD = 1.1. 21) I tend to read books from different genres.: M = 3.4, SD = 1.02. 22) When I see certain black letters (e, n, a, r), I experience them in color (imaginative).: M = 2.2, SD = 1.17. 23) The books were not difficult to read.:

34

M = 4.2, SD = .4. 24) In daily life, I make time to read.: M = 3.2, SD = .75. 25) How the books were

printed and bound, did not bother me.: M = 3.8, SD = 1.17. 26) When I see certain letters in black texts, I do not experience or see (imaginative) any colors, but I do have an automatic association with color.: M = 2, SD = 1.1.

4. DISCUSSION

4.1 Conclusions

This research was chosen as a follow-up study to the study of Colizoli et al. (2012), using the fact that reading in color is a successful method to train synesthetic letter-color associations in non-synesthetes to test whether this training can also be used in non-non-synesthetes with dyslexia. The main goal of this study was therefore to let dyslexics acquire these letter-color associations by reading in color and test the effect of these associations on different reading skills. Two control groups consisting of non-dyslexics are tested using the same tasks before and after reading in color or black and a visual-spatial working memory task (the chessboard task) is added as a control task, as it is unrelated to the training itself.

First, the results from computer tasks and questionnaires will be summarized. No significant difference in reading speed is seen between the two testing sessions in all participants. Likewise, no significant difference in reading speed is seen between groups during both testing sessions. Taking the amount of words the participants read into account, also no significant effect is seen on their average reading speed. Expected was a slower reading speed of dyslexics in group 1 compared to group 2 and 3. In the first testing session, no difference between dyslexics and non-dyslexics is seen in reading speed, so no baseline difference is present between dyslexics and non-dyslexics. It was hoped that the reading in color would have an effect on reading speed, which would show in the second testing session. No increasing effect of reading in color was found on reading speed in any group.

As expected, scores on the chessboard working memory task did not significantly differ between groups during the first testing session. Participants with dyslexia were not expected to perform better or worse on the working memory task compared to participants without dyslexia. No significant difference between the testing sessions is found, as expected. Participants were not expected to perform better on a working memory task during the second testing session after reading in color/black.

During the lexical decision task, participants reacted significantly different at ‘word’-trials compared to ‘non-word’-trials. All participants appeared to be faster in identifying non-words. No

35 main group effect is found on lexical decision performance. Expected was that especially dyslexics would need more time identifying non-words, compared to non-dyslexics. Analysis shows the opposite result in all three groups. Last, no significant difference in lexical decision performance is seen between the two testing sessions. Participants did not appear to react faster or slower to words or non-words in the second testing session compared to the first testing session.

During the Stroop task, both reaction time and accuracy were recorded for each trial. The Stroop effect reflects the difference between incongruent and congruent trials. Most of the participants did seem to react faster on congruent trials compared to incongruent trials, resulting in a positive Stroop effect (see Table 5). No significant differences however, are found in Stroop effects in reaction time between participants or groups. Likewise, no significant effect of testing session is found. Participants do not seem to differ in Stroop effect in the second testing session, after reading in color, compared to the first testing session. For accuracy, also no significant differences are found between groups and between testing sessions. Participants reacted equally accurate to congruent and incongruent trials as well. Expected for the Stroop was an increased Stroop effect in the second testing session thanks to the acquired letter-color associations. These associations were thought to decrease reaction times in congruent trials and increase reaction times in incongruent trials, resulting in a bigger Stroop effect. No such effect is seen after the second testing session in any of the experimental groups or participants. Especially, no distinction can be made between results of dyslexics and non-dyslexics.

4.2 Possible explanations

Expected was a big difference in reading speed between dyslexics and non-dyslexics from the beginning. Dyslexics were expected to read a lot slower compared to non-dyslexics. A possible explanation of the non-existence of this difference is the bias in reading experience within dyslexic participants. This bias can result in a dyslexic group that reads a lot in daily life, decreasing possible reading difficulties. This bias will be further discussed later down.

The absence of significant differences in congruent and incongruent trials of the Stroop can have varying causes. Most participants did react faster on congruent trials compared to incongruent trials, resulting in a positive Stroop effect in reaction time. However, this difference was not significant during the first or the second testing, as well as the difference of Stroop effect between the two testing sessions. Unfortunately, no significant difference between dyslexics and non-dyslexics is found on the Stroop task. In terms of accuracy, all participants were rather accurate in both congruent and incongruent trials, as expected. Before the synesthetic Stroop task, participants received a training for the color-button combinations on the keyboard. The level of difficulty of