Vigilance: Instruction Effects and Personality Correlates of Performance Workload and Boredom

The present laboratory study examined variables that are believed to impact vigilance in operational settings. Instructions were manipulated by telling half of the subjects to relax, and to focus on positive task characteristics (relaxation-emphasis), while the remaining subjects were instructed to "detect as many critical signals as possible" (detection-emphasis). It was expected that instructions emphasizing detection would lead to increased subjective workload ratings, though all subjects participated in the same 30-min vigilance task. Further, it was expected that decreasing demands by emphasizing relaxing qualities of the task would not impact performance, though lower workload ratings were expected. In addition, response bias was manipulated by telling subjects to adopt either a conservative or a liberal criterion. Also, subjects' boredom proneness (BP) and introversion-extroversion (IE) were measured to test the predictive validity of these trait measures in vigilance. Finally, a newly developed Task-related Boredom Scale (TBS) was used to measure the subjective feelings of boredom for the vigilance task. As expected, detection emphasis subjects reported significantly higher workload. Overall performance in hits and A' was not impacted significantly by instructional emphasis (relaxation versus detection), although relaxation-liberal subjects performed more poorly than subjects in the remaining three conditions. Also, BP scores significantly predicted overall hits, A', and boredom ratings, though IE scores did not correlate with subjects' performance directly. The effect of instructional demand on subjective workload indicates that subjects are sensitive to the expectations of experimenters in laboratory vigilance tasks. Also, the predictive validity of the BPS gives evidence for the hypothesized link between trait boredom and monotonous task performance.