Physiological responses during data retrieval: Comparison of constant and variable system response times

摘要

Ten subjects solved 50 database queries consecutively presented on a video display terminal (VDT). Each query required solution within 45 s of its initial presentation to avoid a reduction in potential earnings. A solution required the correct selection of 3 successive hypertext indices hierarchically structured from the query to the data answer. Under a constant system response time (SRT) condition, each selection of a hypertext index was followed by an 8-s delay before another database level, consisting of both indices and data, was presented. Under a variable SRT condition, SRTs varied between 1 and 30 s, with a mean of 8 s. Twenty-five successive queries were presented under each condition, and the order of conditions varied unsystematically across subjects. Systolic blood pressure, mean arterial blood pressure, and heart rate showed pronounced elevations during task performance, in comparison to a resting baseline. Diastolic blood pressure and masseter muscle electromyograph (EMG) response did not change reliably over baseline. Intersubject variability in EMG response was, however, related to heart-rate variability during task performance. No differential physiological effects of SRT conditions were observed. An eleventh novice subject's cardiovascular responses habituated over five successive performance sessions, but when new queries were introduced, heart rate magnitude increased, showing the reversibility of the effect under novel performance demands. These data show that tonic cardiovascular responses may be evoked by a time-pressured and realistic human-computer interaction. The laboratory preparation may emulate functional properties of conditions that prevail in the VDT workplace.