The Simon effect as tool and heuristic.

On its 43rd anniversary the Simon effect can look back at a long and varied history. First treated as a curious observation with implications for human factors research, it slowly evolved not only into a valuable target of psychological theorizing itself but also into a handy means to investigate attentional operations, the representation of space and of one's body, the cognitive representation of intentional action, and executive control. This article discusses the major characteristics of the Simon effect and the Simon task that laid the ground for this success and reviews the major lines of research, theoretical developments, and ongoing controversies on and around the Simon Effect and the cognitive processes it reflects.