Abstract
Abstract: :
Purpose: Immature magnocellular pathways have been proposed to explain the visual processing deficits experienced by dyslexic (poor) readers. If magnocellular pathways control reading, then colored text should not be read faster than black and white text (as suggested by using Irlen lenses), since magnocellular pathways are essentially color-blind. Methods: Computerized reading rates were measured for text that was colored red, green, blue, and yellow, or was white, on a black background, each equated so that contrast was 98% and the mean luminance was 8 cd/m2. We measured reading rates for text that was either unfiltered or filtered to compensate for the child's reduced contrast sensitivity functions, compared to adults. Thirty children in a public elementary school, half being dyslexic, and half being normal readers, 5 each in grades 1, 2, and 3, were studied. The child read continuous text that never repeated from a simple entertaining story. Reading fluency was measured using a double staircase method to measure the speed needed to read 5 words correctly 79% of the time. Results: Colored text was read 30% slower than equiluminant grayscale text, when reading either filtered or unfiltered colored text. This difference was significant, p<0.000001, analyzed using either Student's t test or the Mann-Whitney test. These reduced reading rates did not differ between normal and dyslexic readers. Moreover, filtered text, that activated magno pathways more than parvo pathways, was read twice as fast as unfiltered text, p<0.000001. Conclusion: Colored text makes reading more difficult, showing that colored filters do not improve reading fluency, increasing the saliency of text. This study provides more evidence that magnocellular pathways provide the physiological substrate that controls reading, and not the high acuity parvocellular pathways.
Keywords: 539 reading • 622 visual development • 362 color vision