Sixty male subjects were randomly assigned to one of six experimental conditions an were tested in a driving simulator. The following measures were obtained for each subject: (a) Tracking error (time off the road), (b) speed maintenance, (c) reaction time, (d) meter vigilance, (brake light vigilance, and (f) auditory vigilance. Test sessions involved either four or six hours. In the 4A condition, subjects operated the device for four hours but were required to perform all the tasks during only the first and last hour, in condition 4B subjects operated the device for the first and last hour of the four hour session and were excused during the second hour. In condition 4C, subjects operated the device for the entire four hour session and were required to perform on all tasks during the session. Conditions 6A, 6B, and 6C were similar except a six hour session was involved. In the case of subjects in the 6A condition, they operated the device for the entire session but teats were recorded for only the first and last hour; subjects in 6B were excused during the second trough the fifth hour,while subjects in the 6C condition operated the device for the entire period with data being recorded during the complete session. The following results were obtained: 1) Performance decrements were obtained in the tracking task for subjects in several of the conditions. The most obvious decrements occurred in the six hour conditions (6A and 6C) where performance during the first hour was significantly better than that shown during the last hour. 2) In the speed maintenance task, performance during the first hour also tended to be superior to performance during the last hour. In only the 6C condition were these differences significant, however. 3) Subjects showed an improvement in reaction time during the driving sessions. In each condition, reaction time was faster during the last hour than during the first hour of the task. These differences were significant in the 4C and 6A conditions. 4) There were decrements shown by subjects in several of the conditions on the vigilance tasks. The most apparent decrement occurred in the 6C condition on the meter vigilance task. In the case of the brake light vigilance, a decrement was shown by subjects in the 6C condition while an improvement in performance was shown by subjects in the 4C condition. 5) the results suggest that motivational factors may be of considerable importance in determining the performance of subjects on tasks such as those utilised in the present investigation.
Abstract