THE MAJOR PURPOSE OF THIS RESEARCH WAS TO DETERMINE WHETHER TRAINING IN SPECIFIC COGNITIVE PROCESSES IS EFFECTIVE IN INCREASING THE COGNITIVE FUNCTIONING OF RETARDED CHILDREN. IN PHASE I OF THE PROJECT, 51 EDUCABLE RETARDED AND 18 NORMAL SUBJECTS RECEIVED A 20-DAY PROGRAM IN SIMILARITIES-DIFFERENCES CONCEPT FORMATION AND WERE COMPARED WITH 42 EDUCABLE RETARDED AND 24 NORMAL CONTROL SUBJECTS. CHANGE SCORES FOR THE EXPERIMENTAL AND CONTROL GROUPS ON 30 TEST VARIABLES, INCLUDING CONCEPT FORMATION, REASONING, INTELLIGENCE, AND ACHIEVEMENT TESTS, WERE COMPARED BY T TESTS AND A MULTIVARIATE ANALYSIS OF VARIANCE. THE HYPOTHESIS CONCERNING IMPROVEMENT IN CONCEPT FORMATION WAS STRONGLY SUSTAINED. ALSO GAINS WERE OBSERVED IN RELATED AREAS OF REASONING AND, TO A LESSER EXTENT, IN VERBAL AREAS. HYPOTHESES OF CHANGE IN GENERAL INTELLIGENCE AND ACHIEVEMENT WERE NOT SUSTAINED WHEN SIMILARITIES-DIFFERENCES EFFECTS WERE REMOVED, ALTHOUGH A GENERAL TREND IN FAVOR OF THE EXPERIMENTAL GROUPS WAS NOTED. IN PHASE II, 16 EDUCABLE RETARDED AND 16 BRIGHT NORMAL SUBJECTS RECEIVED A 20-DAY PROGRAM IN COGNITIVE FLEXIBILITY AND WERE COMPARED TO 16 CONTROL SUBJECTS IN EACH GROUP BY A 2 X 2 FACTORAL DESIGN. CHANGE WAS MEASURED BY A FLEXIBILITY TEST BATTERY, COMPOSED OF FIVE SUBTESTS, AND THE STANFORD-BINET INTELLIGENCE SCALE. SIGNIFICANT IMPROVEMENT IN THE PREDICTED DIRECTION WAS FOUND FOR BOTH TEST VARIABLES. IN PHASE III, A TEST AND TRAINING PROGRAM IN THE AREA OF PRODUCTIVITY-RESPONSIVENESS WAS DEVELOPED TO THE TRYOUT STAGE. APPENDIXES INCLUDE DAY BY DAY PLANS FOR (1) THE SIMILARITIES-DIFFERENCES CONCEPT FORMATION TRAINING PROGRAM, (2) THE COGNITIVE FLEXIBILITY TRAINING PROGRAM, AND (3) TEACHERS' MANUAL OF THE PRODUCTIVITY-RESPONSIVE TRAINING PROGRAM. THE FACTOR ANALYSIS OF THE FLEXIBILITY TESTS AND THE COGNITIVE TRAINING EXPERIMENTAL TEST BATTERY ARE INCLUDED. BIBLIOGRAPHY CITES 44 ITEMS. (AUTHOR)