PROBLEM-SOLVING THEORIES IN THREE AREAS - TRADITIONAL (STIMULUS-RESPONSE) LEARNING, COGNITIVE-GESTALT APPROACHES, AND COMPUTER AND MATHEMATICAL MODELS - WERE SUMMARIZED. RECENT EMPIRICAL STUDIES (1960-65) ON PROBLEM SOLVING WERE CATEGORIZED ACCORDING TO TYPE OF BEHAVIOR ELICITED BY PARTICULAR PROBLEM-SOLVING TASKS. ANAGRAM, "INSIGHT,""WATER-JAR," AND ARITHMETIC PROBLEMS WERE CONSIDERED SOLVABLE BY COVERT TRIAL-AND-ERROR BEHAVIOR. IT WAS SUGGESTED THAT "SWITCH-LIGHT," CLASSIFICATION, PROBABILITY-LEARNING, AND NUMEROUS "MISCELLANEOUS" TASKS SHOULD BE APPROACHED BY OVERT TRIAL-AND-ERROR METHODS. BY DISCUSSING PROBLEM SOLVING IN TERMS OF OVERT VERSUS COVERT TRIAL-AND-ERROR BEHAVIOR, THE REPORT PRESENTED A NEW APPROACH TO THE STUDY OF HUMAN PROBLEM SOLVING THROUGH THE USE OF CATEGORICAL IDENTIFICATION OF PROBLEM-SOLVING TASKS. (GC)