Figure 8. Dissociation between use-dependent and action prediction biases.

(A, B) Group average (±within subjects SE) angular errors from each probe target for the two preparation time conditions and fixed targets. Counter-clockwise errors are depicted as positive, such that the pattern of errors in A represents biases toward the centre of the probe target distribution. The inset schematic plots illustrate the locations of the probe (blue) and fixed (red) targets, and the expected bias effects due to pure ‘use-dependent’ effects (red arrows) and ‘action prediction’ effects (blue arrows). Error distributions were similar for the two fixed target conditions (A and B), but were offset towards the fixed target when it was located at 0° (B). As in experiments 1 and 2, bias was greater for short than long preparation time for both fixed targets. However, the differences in errors between the conditions for which the fixed target was at 0° and for which the fixed target was at 45° (C), were similar for all probe targets and both preparation times. This error difference reveals that pure ‘use-dependent’ bias effects of recent movement history are insensitive to movement preparation time.