EXPERIMENTS WERE PERFORMED TO DETERMINED HOW MENTALLY RETARDED AND NORMAL SUBJECTS SYNTHESIZE STIMULI WITH RESPONSES. ALSO, RELATIONSHIPS AMONG THE STIMULUS SYNTHESIS PROCESS, INTELLIGENCE, AND RATE OF LEARNING WERE STUDIED. DISCRIMINATION TASKS WERE USED WHICH REQUIRED SUBJECTS, NORMAL (COLLEGE, HIGH SCHOOL, AND GRADE SCHOOL ENROLLEES) AND MENTALLY RETARDED, TO USE FOUR SEPARATE CUES TO CLASSIFY PICTURES. THE ORDER AND METHODS OF USING THESE CUES WERE THEN STUDIED. FIFTEEN MATHEMATICAL MODELS WERE FORMULATED AND EVALUATED TO DETERMINE THEIR ABILITY TO PREDICT STIMULUS SYNTHESIS PATTERNS. RESULTS RELATED TO LEARNING RATE WERE NOT CONCLUSIVE. THE STIMULUS SYNTHESIS PROCESSES OF MENTALLY RETARDED SUBJECTS DIFFERED FROM THOSE WHO WERE NORMAL. (WB)