Action-specific judgment, not perception: Fitts' law performance is related to estimates of target width only when participants are given a performance score.

Proponents of the action-specific account of perception and action posit that participants perceive their environment relative to their capabilities. For example, softball players who batted well judge the ball as being larger compared to players who did not hit as well. In the present study, we examined this issue in the context of a well-known speed-accuracy movement task that can be examined in the laboratory, repetitive Fitts aiming. In the Fitts task, a performer moved as quickly and as accurately as possible between two targets, D units of distance apart (between 2.5 and 20.0 cm) and of W width (1.0 cm or less). In the Fitts task, we posited that individuals do not have access to performance quality. Thus, we asked whether individual differences in Fitts task performance was related to perception of target width. If Fitts task performance is related to perception of target width, then the action-specific effect on perception does not require explicit knowledge of performance and, furthermore, these effects reside during on-line visual control of the task. We show that only when subjects were provided with a performance score was there a relation between Fitts task performance and target width judgment error. We interpret this result to mean that action-specific effects do not occur during perceptual processing of the task, but action-specific effects are the result of postperformance evaluation processes.