Perturbations of auditory feedback delay and the timing of movement

Among theories concerned with the timing of movement sequences, an important distinction exists between those that assume closed-loop control (in which feedback contingent on one response starts the chain of events that leads to the next response) and those that assume open-loop control (in which feedback does not serve that function). An experiment is reported in which subjects had to make repetitive finger-tapping responses at fixed intervals of 350, 500, or 650 msec. A brief auditory signal was fed back to the subject after each response, and once in each trial, the auditory feedback delay associated with one response selected at random was perturbed by a small amount. It was found that such perturbations affected the immediately subsequent interresponse interval, which is evidence against the simple open-loop model. However, the effects, although in the same direction as the perturbation, were smaller in magnitude, a finding that rejects the simple closed-loop model. In discussing these results it is suggested that subjects operated chiefly in open-loop fashion but monitored the auditory feedback, making compensatory attempts when intervals between auditory feedback events grossly deviated from the desired interresponse interval.