Discrimination shift learning and response inhibition of moderately and severely mentally retarded and non-retarded children.

Simple two-choice discrimination shift learning performances of 20 moderately and severely mentally retarded children were compared with those of 20 non-retarded ones. A learning task arranged with a pair of yellow circle and green triangle slides was used. No difference was found between mentally retarded and non-retarded children in the learning rate of initial discrimination, but the mentally retarded attained shift discrimination more slowly than the non-retarded. Also, the extinction of initial positive responses in mentally retarded children was slower than in non-retarded children. It was suggested that the difficulty of discrimination shift in severely subnormal children is due to failure to suppress a previously learned response to prior positive cues.