THE RESPONSES OF EDUCABLE MENTALLY RETARDED CHILDREN AND INTELLECTUALLY NORMAL CHILDREN OF SIMILAR MENTAL AGES TO TASKS INVOLVING CERTAIN ASPECTS OF LEARNING AND TRANSFER OF THAT LEARNING WERE STUDIED. THE MAJOR OBJECTIVE WAS TO TEST THE HYPOTHESIS THAT DIFFERENCES IN ACHIEVEMENT AND INTELLIGENCE TEST PERFORMANCES BETWEEN THE TWO GROUPS TESTED ARE RELATED TO DIFFERENCES IN THE PROGRESS THEY MAKE IN LEARNING AND TRANSFER. THIRTY ENDOGENOUSLY MENTALLY RETARDED BOYS WITHIN THE IQ RANGE OF 50 TO 75 AND 30 BOYS WITHIN A NORMAL IQ RANGE (100-115) WERE MATCHED INDIVIDUALLY ON THE BASIS OF BINET MENTAL AGE (8, 9, AND 10 YEARS INCLUSIVE). THE MENTALLY RETARDED GROUP WERE SELECTED FROM THE SYRACUSE STATE SCHOOL, AND THE NORMAL BOYS, FROM AN INSTITUTIONAL SETTING. IN ADDITION TO THE DETERMINATION OF THE IQ BY INDIVIDUAL ASSESSMENT, EACH SUBJECT WAS SCREENED FOR ACADEMIC ACHIEVEMENT, AND ADEQUATE VISION AND HEARING. THE SIGNIFICANCE OF ANY DIFFERENCES BETWEEN THE GROUPS IN MENTAL AGE WAS EVALUATED BY MEANS OF THE T TEST. A SERIES OF TESTS, INCLUDING SUCH ITEMS AS CARD SORTING AND PAIRED ASSOCIATES, FURNISHED DATA FOR THE STUDY IN EVALUATING PERFORMANCES OF THE SUBJECTS. (GC)