The main purpose of the present research was to re=examine the Lewin-Kounin theory of cognitive rigidity in the mentally retarded. The scope of this study is on the effect of attentional relevance and cue saliency on the performance of mentally retarded children in concept-switching tasks. Results showed significant differences between groups in the overall number of trials required by the subjects to switch concepts before and after having gone through attentional training. The fact that concept switching can be promoted suggested that persevarative responses are but measures of the strength and attention on a previously reinforced cue. The implication of the findings on the discrepencies in the concept-switching ability found in the subjects of Kounin's sample was also discussed.