Τρίτη, Σεπτεμβρίου 24, 2013
Lots of visual space makes processing text easier for a subset of dyslexics.
Using an e-reader may help some dyslexic students understand what they read, researchers at Harvard University argue.
In a paper published in the journal PLOS One, the authors found that a group of dyslexic teenagers showed greater reading comprehension when using an iPod Touch e-reader than when asked to read from paper. The e-reader was formatted to display around nine lines of text on the screen at a time, with only two or three words in each line, leaving fewer visual distractions. The authors therefore concluded that this improvement is due to the reduced demands on visual attention when reading from the iPod.
The dominant theoretical explanation for dyslexia involves phonological processing, or understanding the sound structure of speech. But there is growing evidence that dyslexia is caused by multiple factors, which can include difficulties in visual attention. It seems that some, though not all, dyslexics have difficulties in processing detailed visual information.
In normal reading, there is a sensitive and highly efficient link between eye movement and understanding. People often believe that when we read, our eyes move continuously and gradually, but that is not the case. Reading involves a series of short eye "jumps" or saccades, followed by a brief period of stillness while the brain processes the letters in front of the eyes. The "visual span" is the number of letters that can be processed during the period of stillness, before moving one’s eyes again.
Problems in the text, such as typos or unknown words, prompt an almost immediate response, with eyes tracking backward and forward to check the surrounding context to help resolve the issue. This shows that we are interpreting what we read word by word, continually updating our understanding.
In skilled reading, this process is so automatic we hardly notice it. However, many dyslexic readers seem to have difficulties, including a shorter visual span and less efficient eye movements. The e-reader means that readers do not need to make these saccades in the same way, and their visual span is less crucial (since the lines of text are so short).
This study shows a significant interaction between visual span and method of reading. Using an iPod improves comprehension in those students with short visual spans, but it reduces comprehension in those with long or good visual spans. This very neatly shows that the visual abilities of the reader are crucial for determining whether this method will be beneficial or not. About a third of the students involved showed a better understanding of what they were reading when using an iPod.
These findings suggest that e-readers may be a useful tool for dyslexic students; however, as the authors state, they would only be an adjunct to direct teaching and practice in reading in multiple contexts. (They also tested adolescent students in a specialized school for children with language learning impairments, so it is not clear that the findings can be extrapolated to older or younger readers, or less severely impaired students.)
The study also has implications for our wider understanding of dyslexia. Historically, the evidence for the causal role of visual impairments in dyslexia has been mixed. Some researchers have argued that, because of the close link between cognition and eye movements, the less efficient eye movements of dyslexic students might be a reflection of their reading problems, rather than a cause.
However, the study shows this is not the full explanation. Simplifying the layout of text actually improves understanding in a third of these students, indicating that the eye movements themselves are making it harder for the dyslexic students to understand what they read.