The ability to self-monitor performance when fatigued

The present study aimed to systematically investigate the effects of elevat ed fatigue levels on the ability to self-monitor performance. Eighteen part icipants, aged 19-26 y, remained awake for a period of 28 h. Neurobehaviour al performance was measured at hourly intervals using four tests from a sta ndardized computer test battery. From these four tests, six measures of per formance were obtained: grammatical reasoning (accuracy and response latenc y); vigilance (accuracy and response latency); simple sensory comparison an d tracking. In addition, before and after each test, participants completed visual analogue scales which required them to rate their alertness level a nd the speed and accuracy of their performance. Individual test results for both self-ratings and neurobehavioural performance were converted to z-sco res. Planned comparison analysis indicated that scores on four of the six p erformance measures decreased significantly as hours of wakefulness increas ed. Similarly, predicted performance scores for all six measures of perform ance decreased significantly. Analysis revealed moderate correlations betwe en predicted and actual performance for the four parameters affected by fat igue. Furthermore, moderate to high correlations were found between all six performance parameters and their respective post-test self-ratings. In add ition, moderate to high correlations were found between predicted performan ce and alertness. Taken together, these findings suggest that as fatigue le vels increase, subjects globally assess performance decrements. Results sug gest that subjective alertness may in part mediate an individual's global a ssessment of performance.