The effect of contrast on reading speed in dyslexia

• Published in: Vision research (Oxford) Vol. 40; no. 14; pp. 1921 - 1935
• Main Authors: O’Brien, Beth A, Mansfield, J.Stephen, Legge, Gordon E
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.01.2000; Elsevier Science
• Subjects: Adolescent; Adult; Analysis of Variance; Biological and medical sciences; Case-Control Studies; Child; Contrast; Contrast Sensitivity - physiology; Dyslexia; Dyslexia - physiopathology; Fundamental and applied biological sciences. Psychology; Humans; Middle Aged; Perception; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Reading; Regression Analysis; Vision; Visual Acuity - physiology; Visual Fields - physiology; Dyslexia; Contrast; Reading; Human; Spatial frequency; Temporal frequency; Visual stimulus; Coding; Developmental stage; Age; Stimulus luminance
• ISSN: 0042-6989; 1878-5646
• DOI: 10.1016/S0042-6989(00)00041-9

Contrast coding has been reported to differ between dyslexic and normal readers. Dyslexic readers require higher levels of contrast to detect sinewave gratings for certain spatiotemporal conditions, and dyslexic readers show faster visual search at low contrast. We investigated whether these differences in early contrast coding generalize to reading performance by measuring reading speed as a function of text contrast for dyslexic children and adults and for age-matched controls. Contrast affected reading performance of dyslexic and normal readers similarly. For both groups, reading speed was relatively constant between 100 and 2% contrast, and decreased rapidly below 2% contrast. This pattern of results held true for both children and adults, for text with and without sentence context, across a range of character sizes, and for reading aloud and reading silently. We conclude that earlier findings of group differences in contrast effects on grating detection or visual search tasks do not generalize to reading.