Subjectively Optimal Delay in Computer Response to a User's Voluntary Action

Abstract

It is typically assumed that the shorter the delay in a computer response to a user's action is, the better. In a study examining this assumption, 16 university students were asked to judge the timing of occurrence of either an auditory or a visual stimulus following a voluntary mouse button-press with various durations of delay from 0 to 400 msec. Both a category scaling and an adjustment method of assessment were used to specify the optimal delay with which the user felt most comfortable. When the delay was 50 msec. or shorter, both auditory and visual responses were judged as too fast to be a consequence of the action. The responses were judged as too slow when the delay was 200 msec. or longer for auditory and 300 msec. or longer for visual stimuli. Analysis for the adjustment method indicated that the optimal delay was within 100 to 200 msec. and was longer for visual than for auditory responses. The present study suggests that immediate responses from a computer are not always comfortable and that the insertion of a moderate delay interval may increase the user's sense of control.