Individual Differences in Low-Level Visual Motion Processing: A Study of Dyslexic Adults and Controls Across Motion Paradigms

Jeremy Wilmer

Department of Psychology, Harvard University

Background and Goals: A number of studies have found a specific deficit in visual motion processing among dyslexic persons. Most previous studies have used one of several variations on a random dot detection paradigm, and one study has used a velocity discrimination paradigm with sinusoidal gratings. One goal of the present study was to replicate both of these previous results, while examining the relative strengths of these two paradigms for isolating such individual differences, specifically: a) their relative power for discriminating these groups, b) their relative association with various measures of dyslexic traits, and c) some of their basic psychometric properties. The second goal was to probe for associations between the two tasks to they whether they might be sensitive to the same sort of individual differences in visual-motion-processing capacities.

Results and Conclusions: In replication of previous results, both motion paradigms differentiated dyslexic participants from controls. There was no clear ‘winner’ in terms of discriminatory power between these groups, and both paradigms were associated to a roughly equal degree with measures of dyslexic traits. The random dot paradigm exhibited more robust psychometric qualities. There was no association between performance on these two tasks across subjects.

Conclusions: This study bolsters evidence for the existence of a generalized (across motion paradigms) visual motion processing deficit in dyslexia. This deficit appears generalized enough so as to be found across motion paradigms that do not show an association with each other across participants. No evidence was found for these two paradigms being sensitive to individual differences in related visual-motion-processing capacities.

The lecture will take place:

In Room 203, 44 Cummington St.
on Thursday, April 4, 2002
at 12:15 pm