Twenty-eight MR children were compared with 28 normal children in a weight dis-crimination test.The ability of weight discrimination in MR children were found markedly lower thannormal children in the tests either with their left hand,right hand,or both hands,though no signifi-cant difference was found among either left and right,or both hands of MR child,implicating that theimpairment of recognition function involved both cerebri hemisphere,not to support the hypothesis ofrecognition dysfunction either in left hemisphere or in right hemisphere dysfunction for MR children.The present investigation also found that MR children showed obvious tendency to make indefinite judgement,which might be a specific response pattern in MR children.