Decision-time measures of sequential processing by mentally retarded and nonretarded adolescents and MA-matched children.

To eliminate the operation of organizational factors during crossmodal information processing, we compared mentally retarded adolescents, CA-matched nonretarded adolescents, and MA-matched children in a same-different decision task in which dyadic sequences were presented within and across the visual and auditory modalities. Decision times for correct "different" responses were greater for the CA-matched group than for the EMR and MA-matched groups, with all groups showing longest times for the visual-auditory dyads and shortest times for dyads in which both stimuli were visual. Differences between the auditory-auditory and auditory-visual dyads were negligible, and increments from visual-visual to visual-auditory dyads were significantly greater than from auditory-auditory to auditory-visual dyads in the EMR and MA groups. Results support a concept of greater visual dominance by the retarded and MA-matched groups rather than slower crossmodal attention switching, per se.