One may define problem solving so broadly as to make the term synonymous with learning. To do so, one needs only to point out that all learning starts with some inadequacy of adjustment, some disturbance of equilibrium-and so, with a 'problem'-and that in the process of achieving adjustment and returning to a state of equilibrium one 'solves' the problem.According to this broad conception, the cat, when it learns to pull the cord or to depress the button and so to escape from the unfamiliar puzzle box; the student in the psychological laboratory, when he learns to run a finger maze while blindfolded or when he memorizes lists of nonsense syllables; the child in school, when he grasps the meaning of a scientific principle and learns how to apply it-all of these engage in problem solving. Again, according to this broad conception of problem solving, practically all research on learning, whether it involves meaningless or meaningful situations, skills or ideational content, laboratory or 'life' conditions, humans or lower animals as subjects-all such research is relevant to the psychology of problem solving.
I. DEFINITIONS OF PROBLEM AND PROBLEM SOLVINGSince all the other chapters in this Yearbook deal in one way or another with learning, the present chapter might appear repetitious, if not redundant. Yet, here is a separate chapter on problem solving. Its presence attests the belief that, for the purposes of education at least, problem solving needs to be considered separately from other kinds of learning. The separation, not an unusual one, 1 is accomplished by defipurpose.