THE PURPOSE OF THE STUDY WAS TO DETERMINE THE EFFECTS OF DIFFERENT SCHEDULES OF MENTAL AND PHYSICAL PRACTICE ON THE LEARNING AND RETENTION OF THREE MOTOR TASKS--USING THE PURSUIT ROTOR AND LEARNING THE SOCCER KICK, AND JUMP SHOT. THREE SEPARATE EXPERIMENTS WERE CONDUCTED IN THREE JUNIOR HIGH SCHOOLS USING 80, 72, AND 60 SEVENTH GRADE BOYS AS SUBJECTS. EACH EXPERIMENT INVOLVED FOUR GROUPS, EQUATED ON THE BASIS OF INITIAL PERFORMANCE SCORES IN THE PARTICULAR LEARNING TASK. EACH GROUP WAS ASSIGNED TO A DIFFERENT PRACTICE SCHEDULE FOR 7 SUCCESSIVE SCHOOL DAYS. THREE OF THE GROUPS FOLLOWED SCHEDULES WHICH INVOLVED BOTH MENTAL AND PHYSICAL PRACTICE IN DIFFERENT PROPORTIONS (75 PERCENT MENTAL-25 PERCENT PHYSICAL, 50 PERCENT MENTAL-50 PERCENT PHYSICAL, AND 25 PERCENT MENTAL-75 PERCENT PHYSICAL), AND ONE GROUP ENGAGED IN PHYSICAL PRACTICE ONLY. PERFORMANCE TESTS WERE ADMINISTERED TO ALL GROUPS AT THE END OF 7 DAYS AND AT THE END OF 3 WEEKS OF NO PRACTICE. THE CONCLUSIONS WERE--(1) A SCHEDULE COMBINING BOTH PHYSICAL AND MENTAL TRIALS CAN PROVE AS VALUABLE IN LEARNING A MOTOR TASK AS A SCHEDULE IN WHICH ALL TRIALS ARE PHYSICAL, (2) WITHIN THE INTELLIGENCE RANGES OF SUBJECTS USED IN THESE STUDIES, IQ SCORES WERE NOT INDICATIVE OF ONE'S ABILITY TO BENEFIT FROM MENTAL PRACTICE, (3) UP TO 50 PERCENT OF THE PRACTICE TIME (OR TRIALS) SPENT IN MENTAL PRACTICE CAN BE AS EFFECTIVE AS 100 PERCENT OF THE TIME SPENT IN PHYSICAL PRACTICE, AND (4) ALTHOUGH SUBJECTS RESPONDED FAVORABLY AND CONSCIENTIOUSLY TO THE SUGGESTION OF MENTAL REHEARSAL, SOME BECAME IMPATIENT WHEN THE TECHNIQUE WAS USED TO EXCESS, UP TO THREE-FOURTHS OF THE PRACTICE TIME. (PS)