How a target's speed influences the extent to which the time or place at which it is intercepted is adjusted.

Abstract

Goal-directed movements are constantly guided by the latest information about the target's position. Nevertheless, movements seldom end perfectly on target, so subsequent movements are adjusted to avoid repeating errors. One could intercept moving targets at different positions at different times, so one could adjust both the position and the timing of the endpoint of both the current and the next movement. It could be advantageous to rely more on adjusting the timing for faster targets, because for faster targets a change in timing corresponds with a larger change in position. We therefore examined how participants responded to 'errors' that were introduced by having slow and fast targets jump slightly backwards or forwards along their path. If there was enough time to adjust the ongoing movement after the jump, timing was indeed responsible for a larger fraction of the adjustment for fast targets. But the actual change in timing did not depend on the target's speed. The same change in timing compensated for a larger part of the error for fast targets, so the position could change less. If there was not enough time to adjust the ongoing movement, neither the timing nor the position on the next trial changed differently for the different target speeds. Consequently, a larger fraction of the error was compensated for if the target moved faster. Thus, how people adjust their timing does not depend on the target's speed, but the same change to the timing has more impact if the target is moving faster.