Independent influences of movement distance and visual distance on Fitts' law.

Fitts' Law is one among a small number of psychophysical laws. However, a fundamental variable in Fitts' Law-the movement distance, D-confounds two quantities: The physical distance the effector has to move to reach a goal, and the visually perceived distance to that goal. While these two quantities are functionally equivalent in everyday motor behavior, decoupling them might improve our understanding of the factors that shape speed-accuracy tradeoffs. Here, we leveraged the phenomenon of visuomotor gain adaptation to de-confound movement and visual distance during goal-directed reaching. We found that movement distance and visual distance can influence movement times, supporting a variant of Fitts' Law that considers both. The weighting of movement versus visual distance was modified by restricting movement range and degrading visual feedback. These results may reflect the role of sensory context in early stages of motor planning. (PsycInfo Database Record (c) 2024 APA, all rights reserved).