Stimulus encoding by mentally retarded and nonretarded adults.

Stimulus encoding was studied with a group of mentally retarded and nonretarded adults. Two sets of 24 nonverbal stimuli were selected; one had a wide range of stimulus structure variables and the other, a representative sample of stimuli. Performance on a match-to-sample task for both stimulus sets was assessed and correlated with the stimulus structure of the standard stimulus. Although there were significant group differences in speed of matching or encoding, matching times for retarded and nonretarded subjects for each stimulus were correlated .97 and .90 for each stimulus set. Correlations of matching times with the stimulus structure variables for each stimulus were very similar for both subject groups. We concluded that both groups encode stimuli in similar ways, but at different rates.