Neuroscience letters
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Fitts' law states that the movement time (MT) of an aiming movement is a linear function of the index of difficulty (ID), where ID = log2(2A/W, A is the movement amplitude, and W is the target width. This law implies that MT should remain unchanged as long as A/W remains constant (i.e. the absence of a scaling effect). The goal of this study was to investigate whether, during upright posture, reciprocal-pointing movements with the center of pressure location follow Fitts' law. ⋯ The results showed that for each A, MT was a linear function of ID. However, the slopes of the linear-regression lines increased with decreases in A. These findings indicate the presence of a scaling effect which violates Fitts' law.