Diving, adaptation, and Fitts law.

To assess Welford's dual controlling factor interpretation of Fitts' law, 20 scuba divers performed a reciprocal tapping task. In an attempt to separate the two factors, the subjects were tested on land and underwater. This does not change the basic parameters of the task but does put the subjects under informational stress, in that underwater the movement is less ballistic in nature and should require the processing of more information (feedback) in each tap. On land, the contributions of movement amplitude and precision were approximately equal. However, the relative changes in contribution of these factors to movement time underwater suggests that these parameters do in fact represent separate controlling factors.