Studies of motion perception in dyslexia have usually used random dot kinetograms with high external noise. Is the reported motion deficit in dyslexia due to deficiencies in
motion perception per se, or due to deficiencies in excluding noise in the displays? In this study, we compared the motion perception thresholds of both dyslexic and nondyslexic children, and dyslexic and non-dyslexic adults using first-order coherent motion displays that varied in noise level and signal salience. Both dyslexic children and adults
had higher motion thresholds than non-dyslexic children and adults when the task
involved first-order motion processing in high noise. Dyslexics performed as well as
non-dyslexics, however, when the signal was clearly separated from the noise or noise
was reduced. Thus dyslexics appear to have normal motion perception, but have
difficulty processing motion in high external noise. The ability to exclude noise or ignore
distractors while focusing on the what is relevant may play a role the creation of
appropriately flexible yet solid phonological and orthographic categories, a fundamental
process in learning to read