Starting with trouble shooting,when system users meet unexpected events such as irregular outputs from the system, they try to identify the causes. The current study aims at understanding how aging influences the identification of the causes such unexpected events. In preceding research, university undergraduate students jointed the experiments. In our study,the identical experimental setting was established, and aged persons participated in experiments. We used a cardgame magic, three card monte, as an experimental task. We compared the performance and the problem solving processes of the aged participants and those of the undergraduate students in the preceding study. As a result, the aged persons’ trick reasoning and problem solving processes remarkably declined compared with the younger participants. It is implied that this may be brought about by the decline of their cognitive abilities. On the other hand, in cooperative problem solving, the aged persons’ performances improved,but did not reach the underguraduates’. The result implies that the improvement was drawn from the interactive conversation between the two participants. The above results suggest that in identifying the causes of unexpected events, aging basically decreases the problem solving performance, however collaboration may compensate for the negative factors of aging.