THE WORK OF AN EARLIER COOPERATIVE RESEARCH PROJECT (NO. 470) WAS EXTENDED THROUGH THIS INVESTIGATION BY COMPARING THE MOTIVATIONAL CHARACTERISTICS AND LEARNING PERFORMANCE OF A GROUP OF INSTITUTIONALIZED MENTALLY RETARDED CHILDREN WITH GROUPS OF SUPERIOR, NORMAL, AND MENTALLY RETARDED NONINSTITUTIONALIZED SUBJECTS. DATA ON THE NONINSTITUTIONALIZED SUBJECTS WERE OBTAINED PARTIALLY FROM THE EARLIER STUDY. COMPARATIVE ANALYSES WERE ACCOMPLISHED BY EXAMINING THE INTERACTIONS OF SELECTED REINFORCEMENT, TASK, AND SUBJECT VARIABLES ON LEARNING PERFORMANCE AND LEVEL OF ASPIRATION BEHAVIOR. PROJECT VARIABLES ARE LISTED BELOW--(1) "REINFORCEMENT" (TYPE SUCCESS OR FAILURE, FREQUENCY, AND ORIENTATION), (2) "TASK" (LEVEL OF COMPLEXITY AND EXTENT OF OVERT VERBALIZATION), AND (3) "SUBJECT" (INTELLIGENCE LEVEL, CHRONOLOGICAL AGE, SEX, AND PLACEMENT TYPE). FOUR SAMPLES OF APPROXIMATELY 100 SUBJECTS EACH (RETARDED, NORMAL, AND SUPERIOR PUBLIC SCHOOL STUDENTS AND RETARDED CHILDREN FROM INSTITUTIONS) WERE ADMINISTERED TASKS INDIVIDUALLY IN CONJUNCTION WITH 12 BASE CELLS, FORMED BY OVERLAPPING THE REINFORCEMENT ORIENTATION AND THE TIME-FREQUENCY DIMENSIONS. MEASUREMENTS OF LEARNING PERFORMANCE AND LEVEL OF ASPIRATION BEHAVIOR WERE MADE. THE REINFORCEMENT VARIABLES DID NOT CONSISTENTLY AFFECT LEARNING PERFORMANCE OR ASPIRATION EITHER SINGLY OR IN COMBINATION WITH ALL OTHER VARIABLES. NEITHER DID THE VARIABLES OF SEX OR PLACEMENT TYPE (INSTITUTIONALIZED AND NONINSTITUTIONALIZED STUDENTS), SINGLY OR IN COMBINATION, HAVE A CONSISTENT EFFECT. ONLY THE LEVEL OF COMPLEXITY VARIABLE, SINGLY AND TO SOME EXTENT IN COMBINATION WITH THE VERBALIZATION VARIABLE, HAD AN EFFECT ON LEARNING PERFORMANCE. EVEN THIS, HOWEVER, HAD NO EFFECT ON ASPIRATION LEVEL. (JH)