Mediation and inhibition deficits in retardate discrimination learning

Investigations into the extent and nature of basic learning deficiencies in mentally retarded children have not yielded consistent results. Although it has often been found that mentally retarded children perform more poorly than normals of similar MA in discrimination learning, a number of alternative hypotheses have been proposed to account for the instances of retardate inferiority. Included among these hypotheses are impaired verbal mediation, defective attention to certain stimulus attributes, deficient inhibitory processes, and inadequate motivation. The lack of consensus which has arisen from the previous research may be due largely to methodological inadequacies which have rendered the findings of many studies ambiguous.\ud \ud A repeated measures design was used to study discrimination learning in moderately retarded and normal children of similar MA. Procedures were incorporated which overcame the weaknesses present in many previous studies. The main purpose was to investigate the above hypotheses concerning the nature of gross learning deficits in the retarded. Certain more general hypotheses about the processes involved in discrimination learning were also examined.\ud \ud Two experiments tested nine hypotheses derived from attention and verbal mediation theories of discrimination learning. The ITPA was used to assess the level of verbal development of the Ss. In general, the results supported attention rather than verbal mediation theories. The retardates, even though markedly inferior in verbal development, were no less able than the normals to exhibit mediational transfer in discrimination shifts. Verbal development was not related in a clear-cut way to mediational capacity in the discrimination tasks. The only result clearly favouring verbal mediation theory was evidence suggesting that the Ss were in a transitional stage of mediational development.\ud \ud Four experiments were concerned with inhibition deficits in retardate discrimination learning. The retardates were not found to be deficient relative to the normals in learning to withhold responses to the negative cue, regardless of whether inhibitory tendencies were rewarded or not. The retarded Ss exhibited a marked deficit in tasks involving the suppression of a previously established habits. A comparison of extinction performance with reversal learning suggested that this deficit had to do with the flexibility rather than the inhibition of established habits. The deficit did not result from inadequate motivation in the retarded Ss.\ud \ud The outstanding implication of the research for remedial education was the pervasive indication of gross inflexibility in retardate performance. It was concluded that urgent attention should be given to devising programs for increasing the flexibility of retardate behaviour