What can eye tracking tell us about reading, writing, and dyslexia? A range of literacy schemes are highly successful Estimated that between 1–33% of the population has reading difficulties Educational practice must continue to be informed by research Eye movement research can inform our knowledge of children’s reading progress Understand what a child must learn to become a skilled reader Will enable a children to transition from learning to read, to reading to learn

Highly sensitive research tool “a window to the mind” To examine developmental changes in the processes associated with reading. Therefore, ideal to study progression from beginner to skilled reader. But also sensitive enough to detect subtle differences in children with dyslexia

What do eye movements look like? Your may have the impression that we scan smoothly over text when we read making very smooth eye movements “Saccade”: ballistic eye movement between words “Fixation”: eyes are relatively still and the majority of lexical processing occurs Eye movements provide a highly sensitive index of the cognitive processing during reading

Rapid decline in visual acuity on the retina Why do we need to make eye movements? Because of the rapid resolution decline from the fovea out on the retina.

This is the area of most detail you would see during a fixation.

Visual acuity is limited to the

Parafovea 15 letters Fovea 8 letters The fovea, which extends about 8 letters during reading If you hold your thumb up, you fovea is the size of your nail. Then slightly less acuity from the parafovea which extends about 15 letters. So eye movements serve to bring the high acuity area to fixate one word after an other when we read. By measuring eye movements we are able to understand the processes involved in reading.

Characteristics of skilled reading A series of saccades and fixations Aim to land a saccade close to centre of a word Not all words are fixated (especially short words) Some words are refixated - most fixation duration ~200ms less than a ¼ of a second The beautiful girl was feeding the birds * - 85% forward saccades,15% backwards saccades The beautiful girl was feeding the birds - 15% content words, 65% function Reading involves a series of highly stylised movements The time when the eyes are still, called a fixation, range between 100 ms and 500 milliseconds, but on average fixations last around 200ms for a skilled adult readers that is less than ¼ of a second. We aim to land a saccade in the middle of a word Around 85% of saccades, move the eyes to right when we read English, but 15% are backward movements, perhaps due to miscomprehension where we want to reread a section of text But not all words are fixated, some words are skipped, this is especially true for short words, around 15% of content words and 65% of function words But some words are fixated more than once. The beautiful girl was feeding the birds The beautiful girl was feeding the birds

Linguistic influences on children’s eye movements gaze duration (ms) Word length – how many letters The girl was feeding the birds beautiful 438 - 88 ms The girl was feeding the birds kind 350 Joseph, Liversedge, Blythe, White, & Rayner, 2009 So what are the main influences on eye movements? There are a range of linguistic influences on eye movements, for example word-length, In a typical study a target word is embedded in the same sentence Child readers typically take longer to read long words than short words, they may also make more fixations on a longer word.

Linguistic influences on eye movements gaze duration (ms) Word length – how many letters Word frequency – how often the word is read The girl was feeding the birds beautiful 438 - 88 ms The girl was feeding the birds kind 350 Joseph, Liversedge, Blythe, White & Rayner, 2009 The kind girl was feeding the birds 459 + 67 ms eagle The kind girl was feeding the 526 Other factors like word frequency, or the amount of time a word appears in books Control for length this time in our target word, and manipulate frequency The time spend reading “birds” a highly frequent word is shorter than reading “eagle” a low frequency Joseph, Nation, & Liversedge, 2013

Linguistic influences on eye movements gaze duration (ms) Word length – how many letters Word frequency – how often the word is read Word predictability – how much a word is expected The girl was feeding the birds beautiful 438 - 88 ms The girl was feeding the birds kind 350 Joseph, Liversedge, Blythe, White, & Rayner, 2009 The kind girl was feeding the birds 459 + 67 ms eagle The kind girl was feeding the 526 And another influence is word predictability, Notice that these differences are less than 100 milliseconds, but eye tracking offers us a highly sensitive tool to understand these influences Joseph, Nation, & Liversedge, 2013 viper The kind girl was feeding the 539 + 80 ms Joseph, Liversedge, Blythe, White, Gathercole, & Rayner, 2008

Linguistic influences on eye movements Eye movements are driven by cognition We move our eyes to subsequent areas of the text once the fixated word is fully processed As long as reading is progressing well, eye movements move from left-to-right (English) But if comprehension breaks down, eye movements are directed back to previously read text These backwards eye movements are known as regressions Reichle, Pollatsek, & Rayner, 2006 Frazier & Rayner, 1982 While Mary bathed the baby slept These backwards eye movements are known as regressions, the example is called a garden path sentence, typically children will take longer to fixate on slept and then make a regression back to an earlier part of the text So naturally a child’s prior knowledge of the world also plays a role in reading

Reading progress influences on eye movements Individual differences are important in understanding how children read Most people score about average We usually refer to these children as “typically developing readers” Number of people Skill ability

Reading progress influences on eye movements Individual differences are important in understanding how children read Sentence reading in a typically developing reader Here is a sample of eye movements during a simple sentence reading task.

Reading progress influences on eye movements Individual differences are important in understanding how children read Most people score about average Some children struggle or excel in reading ability beyond the typical range Number of people Skill ability

Reading progress influences on eye movements Individual differences are important in understanding how children read Sentence reading in a reader with developmental dyslexia And so here is a sample of eye movement data from a child with developmental dyslexia during the same sentence reading task.

Reading progress influences on eye movements How difficult is the reading process for children compared to adults? Typically developing reader Skilled adult reader We know that children find reading more difficult to adults, and you can see that in the number of fixations made, the duration of the fixations and the length of the saccade for example.

Reading progress influences on eye movements How difficult is the reading process for children compared to adults? But also in the number of regressions made, so typically children make more regressions than adults Children typically show longer reading times, make more and longer fixations, shorter saccades, more regressions and refixations and skip less words than adult readers; as age increases, and alongside reading ability, less fixations are required and reading becomes easier and quicker. Kirkby, Blythe, Drieghe, & Liversedge, 2011

Reading progress influences on eye movements How difficult is the reading process for a dyslexic reader? Typically developing reader Reader with developmental dyslexia But there are also differences between groups children of the same age, with and without developmental dyslexia.

Reading progress influences on eye movements How difficult is the reading process for a dyslexic child? Eye movement recordings highlight lexical processing difficulties in children with Developmental dyslexia Comparison between TD readers and readers with developmental dyslexia, eye movement recordings highlight lexical processing difficulties. With more and longer fixations, more regressions, rarely skipping words, longer total reading times Kirkby, Blythe, Drieghe, & Liversedge, 2011

Eye movements clearly highlight lexical processing difficulty But how do we isolate dyslexia from reading ability?

Matching comparison groups   Dyslexic Group Age matched controls Word reading 84.5 110 Pseudoword reading 87.5 RAN letters  90 105.5 RAN numbers 91 107 Chronological age 10y 8m Reading age 8y2m 11y2m IQ 113 115 Reading-age matched controls 103 95 102 8y 0m 8y2m 112 As reading ability influences eye movements we really need to include another group. So we now include a reading age matched comparison group so that we can see if these differences between groups is a function of dyslexia or a function of reading ability?

Basic characteristics of eye movements for child groups   Dyslexic readers Chronological-age match Reading-age matched Fixation duration 307 ms 245 ms 294 ms Saccades amplitude 1.92° 2.31° 2.11° Number of fixations 24 16 20.5 Total sentence reading time 7818 ms 4080 ms 6711 ms Regression frequency 32% 26% 29% So then when we add in this third group we still see small but significant differences in the characteristics of eye movements during reading

Reading progress influences on eye movements Gaze durations

Reading progress influences on eye movements So there are substantial differences in foveal word recognition between these groups

We know that dyslexic readers are processing text differently We have seen that eye tracking can detect these small differences So why would there be a difference?

Listening vs. reading Listeners Readers can potentially access all the information in the fovea and parafovea. But do they use all of it? Only information from the line they are reading Mostly information to the right of fixation receive information one word at But readers can poten a time

Measuring the extent of parafoveal processing Preprocessing: Gaze-contingent boundary paradigm (Rayner, 1975) There was a magic dragon in the kingdom. There was a magic rdagon in the kingdom. There was a magic jvagon in the kingdom. Preview benefit effect Fixation dragon dragon 1 511 552 616 2 315 337 340 3 450 481 505

Calculating preview benefit Preview identical condition: fixation time on dragon = 315 ms There was a magic dragon in the kingdom. Preview transposed letters: Fixation time on dragon = 347 ms There was a magic rdagon in the kingdom. Preview substituted letters: Fixation time on dragon= 387 ms There was a magic jvagon in the kingdom. Preview benefit = 72 ms Transposed letter effect = 40 ms 511 552 616 Transposed-letter effect in skilled reading taken as evidence for a language processing system that extracts letter identity information independent to absolute letter position (Johnson, Perea, & Rayner, 2007) Under specification of letter position encoding, however, has been causally linked to developmental dyslexia (e.g. Friedmann & Rahamim, 2007)   These results and comparable results for adult dyslexic readers showed disruption in reading for previews with transposed letters and substituted letters compared to baseline identical previews With less disruption from transposed letter previews compared to substituted letter previews The typical transposition effect observed in dyslexic readers has important implications for the causal role of letter position encoding in dyslexia therefore, there seems to be processing occuring prior to fixation for readers with dyslexia and the typical flexibility of letter position encoding. 95 64

We know that dyslexic readers are using all the same information to the right of fixation compared to reading-age and chronological-age matched readers So something else must be going on, what are dyslexic readers doing differently?

The Magnocellular Theory: Binocular coordination (Kirkby, White, & Blythe, 2011)

Testing the Magnocellular Theory If dyslexia caused by impaired binocular coordination Increased binocular disparity - in dyslexic individuals during reading and non-linguistic task If dyslexia causes disruption to binocular eye movements during reading Increased binocular disparity should occur only during reading

Eye Movements (Kirkby, Blythe, Drieghe, & Liversedge, 2011)

Binocular coordination During Dot Scanning During Reading

Binocular coordination was affected by the task The Results Showed Children with dyslexia have increased disparity during reading compared to dot scanning Binocular coordination was affected by the task Fixation disparity was significantly greater for dyslexic readers Adults’ & typical child readers’ binocular coordination equivalent The results from the study showed: (i) children with dyslexia have an increased magnitude of fixation disparity when they are reading compared to dot scanning – within the same group of children, binocular coordination was affected by the task; (ii) in comparison with other participant groups, when reading, the magnitude of fixation disparity was significantly greater in the dyslexic children; and (iii) adults’ and typically developing children’s binocular coordination was equivalent, and this was the case during both reading and dot scanning.

Conclusions Poor binocular coordination is unlikely to play a causal role in dyslexia Our data suggests that when dyslexic readers look at words there is something different about their binocular coordination Importantly, however, poor binocular coordination is unlikely to play a causal role in these children’s reading difficulties. Clearly, our data represent a stimulus specific-deficit in regard to binocular coordination.

How can we help dyslexic readers access text Increasing inter-letter spacing found to improve legibility of text –shown in French, Spanish, Italian child readers (Perea et al., 2012; Zorzi et al., 2012) We find similar benefit in English dyslexic readers Our pattern of effects suggest this is especially effective for children with dyslexia Appling this simple technique to eBooks for example, can potentially improve the accessibility of text for dyslexic readers The beautiful girl was feeding the birds T h e b e a u t i f u l g i r l w a s f e e d i n g t h e b i r d s

Dyslexia Friendly Classroom BDA – Dyslexia Friendly Classroom - difficulty in copying from the board Classroom learning relies heavily on copying and note-taking Copying from a board presents serious difficulties to almost all learners with dyslexia Psychologically complex task, involving visual-encoding, construction and maintenance of a mental representation in working memory, production in written form Do children engage in meaning or just pattern copying? Visual-encoding How much can children accurately remember and write? lexical access mental representation Do children read and fully understand information they copy? written production

Using mobile eye tracking The Dikablis mobile eyetracker allows us to record eye movements during a task in which children are not required to keep still! The mobile eye tracker links the location of the eye with the objects in the environment to work out what children are looking at and how long they spend processing

Study skilled adult readers children aged 7-10 Task To copy individually presented words from a whiteboard in a classroom

What did this look like in practice?

Initial encoding time Adults Lexical influence on long words, advantage for high frequency Similar trend in short words Children Lexical influence on short words, advantage for high frequency No lexical influence on long words stable fixation initial encoding writing onset secondary end verification trial

Initial encoding time Adults Lexical influence on long words, advantage for high frequency Similar trend in short words Children Lexical influence on short words, advantage for high frequency No lexical influence on long words stable fixation initial encoding writing onset secondary end verification trial

Initial encoding time Adults Lexical influence on long words, advantage for high frequency Similar trend in short words Children Lexical influence on short words, advantage for high frequency No lexical influence on long words – if anything, there is a reverse frequency influence stable fixation initial encoding writing onset secondary end verification trial

Written production Both adults and children showed very similar patterns in writing Word length influences writing processing time There is no robust influence of word frequency in processing writing stable fixation initial encoding writing onset secondary end verification trial

Summary of copying findings What does this mean? In sentence reading, children are capable of reading long, low frequency words But during copying, children do not always process these words as whole words Break them down into clusters of letters to make the task easier Why is this important? Children can write accurately and efficiently without processing the meaning of the words Impact on learning Even if children do read the whole word, during written production, smaller sublexical units seem more important during the writing process

Summary Eye movements provide a highly sensitive index of the cognitive processing during reading Eye movements clearly highlight lexical processing difficulty in dyslexic readers We know that dyslexic readers are processing text differently We know that dyslexic readers are using all the same information to the right of fixation compared to reading-age and chronological-age matched readers We know that when dyslexic readers look at words there is something different about their binocular coordination A simple technique of adding spaces between letters can, potentially, make text more accessible for dyslexic readers But during copying, even typical readers do not always read words as whole words, instead they break them down into clusters of letters to make the task easier but may not access the meaning