ABSTRACT
In the area of perceptual-motor behaviour, there are very few relations between important performance-defining variables that remain unchanged across different participant groups and environments. The relationship between movement time and movement accuracy in goal-directed aiming/reaching is the exception. The covariation between these two variables is stable across so many contexts that this relation has come to be known as Fitts’ Law. Paul Fitts found that mean movement time increased systematically with the accuracy requirements, as defined by the amplitude of the movement and the size of the target. This relationship was observed for both reciprocal (Fitts, 1954) and discrete aiming movements (Fitts and Peterson, 1964). Specifically:
Mean Movement Time = a + b [log2(2x Movement Amplitude/Target Width)] Where a and b are empirical constants that depend on the specific performer
and task conditions.
