Adaptation to visual feedback delays in a human manual tracking task.

The time-course of human adaptation to spatial perturbations of visuomotor function (e.g. with prisms) is very short. However, it is not clear how rapid the adaptation to other aspects of perturbed feedback is. In this paper we report the adaptation to delayed visual feedback. Three groups of six subjects tracked unpredictable, continuously moving targets using a hand-held joystick while visual feedback of the joystick position was delayed (0 ms, 200 ms or 300 ms). Subjects clearly adapted to the delay, with a significant drop in tracking error, but changes in more subtle aspects of their tracking behaviour (such as changes in intermittency and their "impulse response functions") were not consistently observed. We suggest that the adaptation seen was consistent with the idea of there being a "delay component" in the internal processes used in manual tracking, as proposed in models such as the Smith predictor model.