Figure 1.

Experimental design and example data. A, Experimental setup. Participants made planar reaching movements to targets presented via a mirrored display. B, Free RT condition (left) and Forced RT condition (right). In the Free RT condition (left), a single target appeared at an unknown location at a predictable time (cued by a series of 4 tones), and participants were instructed to move as soon as the target appeared. In the Forced RT condition (right), participants were instructed to move synchronously with the fourth tone. RT was manipulated by varying the time that the target was presented relative to the time of movement onset. C, Behavior of a representative participant. Green histogram indicates the distribution of RTs in the Free RT condition (both correct and incorrect movements). Blue circles indicate RT (x-axis) and directional error (y-axis) for each trial in the Forced RT condition. Gray region indicates the range of directions considered to be accurate.