Cognitive controls and mental retardation.

A color-digit interference task and two sorting tasks were devised as variants of the Stroop Color-Word Test and Gardner's Sorting Tasks, respectively. These tasks proved applicable to a mentally retarded sample and provided reliable measures of two cognitive control dimensions (constricted-flexible control and equivalence range). As predicted, the main test scores were significantly more variable in retarded, compared with normal, 5s. Analyses of performance on the color-digit interference task indicated that retarded 5s were significantly slower than the normal 5s on all parts of the task, particularly under conditions of distraction (whether inherent in the task or externally imposed). Low IQ retarded 5s were significantly slower than high IQ retarded 5s on all parts of the task. Discussion focussed on the extreme cognitive control test scores of the retarded 5s, the nature of the attentional deficit among these 5s, and the relevance of a cognitive control approach for the training of retarded persons.