Surprise! Why Insightful Solution Is Pleasurable.

Insight problems-as a type of ill-defined problems-are often solved without an articulate plan, and finding their solution is accompanied by the Aha! experience (positive feeling from suddenly finding a solution). However, the solution of such problems can also be guided, for example, by expectations in terms of criteria for achieving the goal. We hypothesize that adjusting the expectation accuracy based on the reward prediction error (discrepancy between the reward and its prediction) affects the strength of affective components of the Aha! experience (pleasure and surprise), allowing to learn how to solve similar problems. We manipulated expectation accuracy by varying the similarity in problem solution principle and structure in a short learning set. Each set was followed by a critical problem where both the structure and solution principle were changed (except for control set). Subjective feelings, solution time, and expectation were measured after each problem. The results revealed that problems with similarities become more expected at the end of the set and their solution time is decreased. However, the critical problem featured a rapid increase in pleasure and surprise and decrease in expectedness only in the condition where both the solution principle and structure were expected, suggesting that problem structure is a key feature determining expectedness in insight problem solving. The Aha! experience is not an epiphenomenon; it plays a role in learning of problem solving through adjusting expectations.