Experimental investigation of psychophysiological stress-reactions induced by different system response times in human-computer interaction∗

Abstract

In human-computer interaction, system response times are considered to have important effects on operator performance and stress response. To evaluate the effects of short (2s) and long (8s), as well as constant and variable, system response times, a laboratory study was conducted with 68 subjects in four independent groups working at a simulated computer workplace. Subjects had to perform a simple detection and correction task at a visual display terminal in six trials of 20min each, the first being a training trial with identical conditions for all subjects. Performance and physiological measures (heart rate, electrodermal activity, and blood pressure) were taken during the trials, and subjective measures of mood and physical state as well as physiological measures were done in the resting periods iiftcr the trials. In addition to a general adaptation effect over the trials, experimental effects were shown mainly for the duration factor: subjects under conditions of long, as compared to those under short, system response times showed a lower mean error rate (p < 0·01) in the performance measures without differences in work speed. In the physiological measures, lower levels of systolic blood pressure (p < 0·05) were seen under long system response times, but a greater number of skin conductance reactions (p < 0·05). Pain symptoms (headache, p < 0·05; eye pain, p < 0·05) were more pronounced under short system response times. The results are interpreted as differential effects of duration of system response times on variables indicating stress responses. In general, the results obtained in this study confirm the results of a previous pilot study. Further research will be necessary to evaluate the effects of system response time variability.