Previous studies suggested that heuristics sometimes obstructed solving particular insight problems (e.g. Knoblich,1999). Abe & Nakagawa (2008) took up the Cheater Detection Model (CDM: Cosmides, 1989) as an adaptive heuristic withinsocial environment, and suggested that it has a negative influence on the ‘missing dollar’ riddle. In this study, we examined thesame type of insight problem from a different point of view, i.e., the balance of loss and gain. We made two isomorphic riddles:in one riddle some amount of money was lost and was never found (the loss condition), and in another riddle the same amountof money was spent for additional service (the benefit condition). The percentage of correct answer was significantly higher forthe latter. The result suggested that the balance of loss and gain influenced the cognitive set of the participants. The occurrenceof loss might draw their attention on outflow of the money.

Since Johanson (1973), it is well known that people perceive human behavior, not only familiar ones such as walking and dancing but also unfamiliar behaviors in point-light display. While categorization among well-known behaviors has been well studied, it is not clear yet how people extract the cues that are useful for perceiving unfamiliar behaviors. We hypothesized that the hierarchical information in human structure was playing an important part for perception of unfamiliar behaviors, and examined this hypothesis by comparing performances of three kinds of models in categorization tasks of unfamiliar arm movements. While the first model was based only on local motion of the point lights, the second model used hierarchical ordering information to analyze the local motion. The third model used strict positioning following the hierarchical structure in addition to the ordering information. The comparison suggested that hierarchical ordering was important information to producing close performance to human performance.