The effects of stress fatigue on performance in a driving device.

Fifty-four male subjects were randomly divided into three equal groups and tested in a simulated driving device. The following measures were obtained for each subject: (a) tracking error, (b) speed maintenance, (c) reaction time, and (d) vigilance. The Latter consisted of two visual vigilance tasks, meter vigilance and brake light vigilance. In one of the groups, designated the contingent shock group, subjects received an electrical shock based on their performance on the various tasks. preliminary work suggested that his group had a higher level of emotional arousal than the other two groups.In the second group: subjects received random shock with no relationship between shock and performance. The third group, which was considered the control group, received no shock. Test sessions in the device were six hours in duration. The third group, which was considered the control group, received no shock. Test sessions in the device were six hours in duration. The following results were obtained. 1) In the tracking task no significant differences were found between groups. However, analysis of variance showed a significant difference existed between trials. In this case, a trial consisted of a one hour period of operation of the device. Further analysis showed that the contingent shock group had significantly higher tracking error during the last two hours of the task than during the earlier hours. 2) Reaction time was significantly higher in the contingent group during the last two hours than during the second, third, and fourth hour. 3)During hours four, five, and six, significantly more signals on the meter vigilance task were missed by subjects in the contingent shock or control groups. No difference between groups or between trials were found in the brake light vigilance task. 4) Significant differences existed between speed maintenance scores of the contingent shock group and the other two groups during the fifth and sixth hour of the session. Results are discussed in terms of Crawford's (2) concept of stress fatigue. Finding in the study sypport the idea that stress brings about an emotional arousal which may interfere with performance on tasks such as driving.