Intelligent Testing has a good post on Dyslexia and Eye Tracking that examines a study demonstrating dyslexics, contrary to popular opinion, any eye-tracking problems a dyslexic may have are correlational to dyslexia rather than the cause.
The original study used two techniques to simulate the eye-tracking needed for reading without requiring actual reading: Psuedowords like DREV and GINZ and constant strings like QQGP and DMGL. By using these, the researchers could study eye-tracking without worrying that another possible causes of dyslexia, such as phonic problems, was effecting the dyslexics.
The researchers found that dyslexics and non-dyslexics performed equally well on the constant string reading test but dyslexics were worse on the psuedowords test. This suggests that dyslexics do not have a fundamental problem in eye-tracking and reading letters but that a problem arises when they try to process words.
An interesting conclusion that the researchers draw from the results is that:
…is that dyslexic readers’ eye movements during reading are neither dysfunctional nor erroneous – but a mirror of their reading difficulties.
Meaning that if a dyslexic has a reading age of five then their eye-tracking ability will also be that of a five year old. This matches similar research on dyslexic’s reversing letters that found dyslexics do it no more often than children of the same reading age. This raises an interesting question of what happens if you train a dyslexic’s visual abilities up to his natural age? Will their reading abilities rise to match their visual-skills age?
One criticism of this study is that the actual tests used in it are too short, each only equivalent to reading thirty to sixty words. I would like to have seen some examination of the dyslexic’s performance over a period equivalent to how the children are expected to read in class. The study was conducted on 13 year olds who are expected by the education system to read for a lot longer than a couple of minutes.
A longer reading period would of investigated the effects of reading fatigue, a common complaint of dyslexics. If the dyslexics’ constant string reading ability decreased over time faster that the non-dyslexics then it would be logical to conclude that dyslexics do have great problem with eye-tracking in real world situations. Repeating the tests multiple time would of also been interesting. Would non-dyslexics improve through practice at a faster rate than dyslexics thus suggesting that dyslexics lack an ability to learn or optimise their eye-movements?
Full Study: Perhaps correlational but not causal: No effect of dyslexic readers’
magnocellular system on their eye movements during reading [PDF]