Standardized task strain and system response times in human-computer interaction.

Involuntary delays in human-computer interaction, for example, system response times (SRTs) can increase stress. In the present study, 40 college-age subjects were randomly divided into an 'incentive' and a 'non-incentive' group'. Subjects performed a computer task with SRTs of 0.5, 1.5, and 4.5s. Physiological, subjective, and performance data were collected during the task. The computer task was designed to individually set difficulty level (i.e., mental strain), thus standardizing the task for all subjects. By using this procedure, changes resulting from SRT duration can be separated from the effects related to task difficulty. The results indicate that both short and long SRTs produced differential psychophysiological changes consistent with different types of stress responses. Short SRTs resulted in higher autonomic and somatic activity, increased positive self-reported emotional states but poorer performance. Long SRTs resulted in increased electrodermal activity, negative self-reported emotional states and better performance.