Researchers have long noted that readers with dyslexia employ eye movements that are significantly different from non-dyslexics. While these movements have been studied in small sample sizes in the past, a paper written by Concordia researchers and published in the Nature journal Scientific Reports looks at a much larger group.
The study used eye-tracking technology to record the movements and concluded that people with dyslexia have a profoundly different and much more difficult way of sampling visual information than normal readers.
“People have known that individuals with dyslexia have slower reading rates for a long time,” says the paper’s co-author Aaron Johnson, an associate professor and chair of the Department of Psychology.
“Previous studies have also looked at eye movement in adult dyslexics. But this paper quite nicely brings these together and uses behavioural measures to give us a full representation of what differences do occur.”
The eyes have it
Dyslexia researchers use several metrics to measure eye movements. These include fixations (the duration of a stop), saccades (lengths of a jump), and counting the number of times a reader’s eyes express a jump. Traditionally, dyslexia researchers would use a single sentence to measure these movements. Johnson and his co-authors used instead standardized identical texts several sentences long that were read by 35 undergraduate students diagnosed with dyslexia and 38 others in a control group.
The researchers wanted to address a core question in the field: are reading difficulties the result of a cognitive or neurological origin or of the eye movements that guide the uptake of information while reading?
“We saw that there was a real spectrum of reading speed, with some speeds among the dyslexic students as low as a third of the speed than that of the fastest readers in the control group,” says lead author Léon Franzen, a former Horizon postdoctoral fellow at Concordia’s Centre for Sensory Studies now at the University of Lübeck in Germany.
“But by using a variety of measures to put together a comprehensive profile, we found that the difference in speed was not the result of longer processing times of non-linguistic visual information. This suggested there was a direct link to eye movements.”
Franzen notes that when the participants with dyslexia read a text, they paused longer to uptake the information but they did not have any trouble integrating the word meanings into the context of a sentence. That behaviour is seen commonly in children who are learning to read. Adults who read at normal speeds do not exhibit those pauses and eye movements.
“Dyslexia is a development disorder that begins in childhood,” explains Zoey Stark (MA 21), the study’s second author. “It often goes undiagnosed until the child experiences real difficulties.”
A consequence of poor reading, not a cause
While some researchers believe ‘faulty eye movements’ is a cause of dyslexia, others believe that the eye movement abnormalities seen in dyslexics are attributable to their language problems. According to Stanovich, the relationship of certain eye movement patterns to reading fluency has repeatedly, and erroneously, been interpreted as indicating that reading ability was determined by the efficiency of the eye movements themselves.
Stanovich continues to say, “Poor readers do show the inefficient characteristics listed above, but they are also comprehending text more poorly. In fact, we now know that eye movements rather closely reflect the efficiency of ongoing reading … and this is true for all readers, regardless of their skill level. When skilled readers are forced to read material too difficult for them, their eye movement patterns deteriorate and approximate those usually shown by the less skilled reader. The eye movement patterns of the latter look more fluent when they are allowed to read easier material. In short, the level of reading determines the nature of the eye movement patterns, not the reverse.”
If you suspect that your child has dyslexia, contact your closest Edublox clinic for an assessment and help.