The Effect of System Response Times on Temporal Predictability of Work Flow in Human-Computer Interaction

Abstract

Studies on the effect of enforced waiting periods in human-computer interac- tion caused by system response times (SRTs) have shown that work style and psychophysiological stress level are markedly influenced by the mean SRT length but hardly by SRT variability, although the latter is supposed to induce temporal uncertainty which is well known as a potent stressor. Hence, this study tests the hypothesis that temporal uncertainty can be induced by SRTs without any variability when their duration is so large that the user cannot ac- curately anticipate the next work step because of his or her limited temporal sensitivity. Reaction time (RT) measures on simulated system breakdowns show that accuracy of temporal anticipation of the next work step under SRTs between 2 and 8 sec is much worse than results of psychophysical stud- ies on time perception would predict, and deteriorates deviating from Weber's Law when SRT length exceeds 6 sec. Completion time of work steps, varied as a second factor, shows no significant main effects on predictability. The result suggests that predictability of work flow is markedly affected by long SRTs leading to changes in work style as shown by performance measures.