Investigating sleepiness and distraction in simple and complex tasks

The cost of sleepiness-related accidents runs into tens of billions of dollars per year in America alone (Leger, 1994), and can play a contributing role in motor vehicle accidents and large-scale industrial disasters (Reason, 1990). Likewise, the effects of an ill-timed distraction or otherwise lack of attention to a main task can be the difference between elevated risk, or simply a lack of productivity. The interaction between sleepiness and distraction is poorly researched, and little is known about the mechanisms and scale of the problems associated by this interaction. Therefore, we sought to determine the effects of sleepiness and distraction using overnight and daytime sleepiness with various levels of distraction on three tasks ranging from a simple vigilance task to a challenging luggage x-ray inspection task. The first and second studies examined overnight sleepiness (7pm to 7am) for twenty-four healthy participants (m = 23.2yrs old - same for both studies) using a psychomotor task compared to a systems monitoring task, while also manipulating peripheral distraction through a television playing a comedy series. The results showed significant effects of sleepiness on the psychomotor task and evidence for interactive effects of distraction, whereas the systems monitoring task showed no changes with either sleepiness or distraction. Subjects were far more prone to distraction when sleepy for both tasks, and EEG findings suggest that the alpha frequency (8-13Hz) power increases reflect impairments of performance. There is a decaying . exponential relationship between the probability of a subject's eyes being open as the response time increases, such that longer responses above three seconds are 95% likely to have occurred with the eyes closed. The third study used a sample of twelve young (m = 20.8yrs) and twelve older (m = 60.0yrs) participants, and examined the effects of sleep restriction « 5hrs vs normal sleep) with three levels of distraction (no distraction, peripheral in the form of television and cognitive distraction as a simulated conversation by means of verbal fluency task). The task used was an x-ray luggage search simulator that is functionally similar to the task used for airport security screening. The practice day showed that speed and accuracy on the task improved with successive sessions, but that the older group were markedly slower and less accurate than the younger group even before the experimental manipulations. There was no effect of daytime sleep restriction for either the younger or older groups between the two experimental days. However, distraction was found to impair the performance of both young and old, with the cognitive distraction proving to be the most difficult condition. Overall, it is concluded that overnight sleepiness impairs performance in monotonous tasks, but these risks can be diminished by making tasks more engaging. Distractions can affect performance, but may be difficult to quantify as subjects create strategies that allow themselves to attend to distractions during the undemanding moments of a task. Continuous cognitive distraction does affect performance, particularly in older subjects, who are less able to manage concurrent demands effectively. Humans appear capable of coping Sleepiness and Distraction iv with a 40% loss of their usual sleep quota or 24-hours of sleep restriction on complex tasks, but performance degrades markedly on monotonous tasks. Performances for simple and complex tasks are impaired by distracters when the effect of distraction is large enough, but the magnitude of impairment depends on how challenging the task is or how well the subject is able to cope with the distractions.