THE GENERAL PROBLEM UNDER INVESTIGATION CONCERNED TWO PROCESSES OF CONCEPT FORMATION - THE DEDUCTIVE REASONING PROCESS AND THE ASSOCIATIVE PROCESS - EMPLOYED BY CHILDREN OF ELEMENTARY-SCHOOL AGE. IT WAS ASSUMED THAT BOTH OF THESE PROCESSES ARE FOUND IN VARYING DEGREES AMONG CHILDREN OF DIFFERENT AGES AND MENTAL ABILITIES, DEPENDING UPON THE CHARACTERISTICS OF THE PARTICULAR TASK. THE FIRST TWO EXPERIMENTS WERE CONCERNED WITH THE INTERACTION OF BOTH OF THESE PROCESSES IN A CONCEPT FORMATION TASK, WHILE SUBSEQUENT EXPERIMENTS REPRESENTED AN ATTEMPT TO FOCUS UPON THE ASSOCIATIVE PROCESS BY STUDYING ITS OPERATION IN A VARIETY OF SITUATIONS. CONSISTENT INDICATIONS APPEARED THAT, WHEN LARGE AND SMALL VARIETIES ARE EQUAL IN STRENGTH, A SMALL VARIETY IS LIKELY TO PROMOTE CONCEPT ATTAINMENT TO A GREATER EXTENT THAN A LARGE VARIETY. IT WAS ALSO FOUND THAT IT IS POSSIBLE TO CONSIDER THE ROLE OF VARIETY IN THE ATTAINMENT OF CONCEPTS AS A FUNCTION OF THE DEDUCTIVE AND ASSOCIATIVE PROCESSES WHICH CAN BE ASSUMED TO OCCUR, ALTHOUGH IN VARYING DEGREES, AS A FUNCTION OF THE DEMANDS OF THE TASK AND SUBJECT CHARACTERISTICS. (GD)