Effects of test anxiety, tests, and sleep on children''s performance

This study examined the interrelationship between children's test anxiety, sleep, and performance. The subjects, 239 sixth and seventh graders, responded to questionnaires examining sleep behavior and test anxiety on a day when they had a major exam in school, and on a day when they did not. They also completed a vigilance task on both days. The results showed that partial sleep loss (i.e., under 3 hr) did not adversely influence subjects' performance on the vigilance task or on the actual class exam. However, the results did reveal that test anxiety was negatively related to performance on the class exam.     

Use of Stimulants to Ameliorate the Effects of Sleep Loss During Sustained Performance

A variety of experimental approaches is presently under investigation to study the impact of stimulant drugs on anticipated decrements of performance due to sleep loss and sustained operations. The drugs have been used either in a preventive (maintenance) paradigm designed to maintain behavior over long periods of time or in a recovery paradigm designed to offset the effects of sleep deprivation and/or sustained performance. Several such studies are reviewed and their results evaluated. Questions concerning theoretical and practical applications are raised, and suggestions for future research are discussed.     

The effects of task duration and work-session location on performance degradation induced by sleep loss and sustained cognitive work

Studies attempting to estimate the degree of performance degradation resulting from sleep loss typically use relatively long-duration tasks that are distinctly separate from ongoing activities. Since long-duration tasks are not practical for assessing the performance degradation induced by sleep loss in field settings, this study was designed to examine whether the results of short-duration (1-min) tasks were markedly different from those of long-duration (10-min) tasks with respect to detecting performance changes during a 54-h period of sleep loss and sustained cognitive work. Performance changes also were examined as a function of the location of tasks within work sessions by comparing performance on 1-min tasks that were placed within work sessions with those tasks that immediately followed short rest periods. The results showed that short-and long-duration tasks were equally sensitive to sleep loss. In addition, once sleep-deprivation effects began to emerge, it was found that performance on short-duration tasks within work sessions showed significantly more impairment than performance on tasks that followed rest breaks. These results suggest that task duration is not a critical factor for detecting performance degradation induced during continuous work experiments but that the location of tasks within work sessions is critical for accurately assessing expected performance.     

Computational cognitive modeling of the temporal dynamics of fatigue from sleep loss

Computational models have become common tools in psychology. They provide quantitative instantiations of theories that seek to explain the functioning of the human mind. In this paper, we focus on identifying deep theoretical similarities between two very different models. Both models are concerned with how fatigue from sleep loss impacts cognitive processing. The first is based on the diffusion model and posits that fatigue decreases the drift rate of the diffusion process. The second is based on the Adaptive Control of Thought – Rational (ACT-R) cognitive architecture and posits that fatigue decreases the utility of candidate actions leading to microlapses in cognitive processing. A biomathematical model of fatigue is used to control drift rate in the first account and utility in the second. We investigated the predicted response time distributions of these two integrated computational cognitive models for performance on a psychomotor vigilance test under conditions of total sleep deprivation, simulated shift work, and sustained sleep restriction. The models generated equivalent predictions of response time distributions with excellent goodness-of-fit to the human data. More importantly, although the accounts involve different modeling approaches and levels of abstraction, they represent the effects of fatigue in a functionally equivalent way: in both, fatigue decreases the signal-to-noise ratio in decision processes and decreases response inhibition. This convergence suggests that sleep loss impairs psychomotor vigilance performance through degradation of the quality of cognitive processing, which provides a foundation for systematic investigation of the effects of sleep loss on other aspects of cognition. Our findings illustrate the value of treating different modeling formalisms as vehicles for discovery.     

Sleep, watchkeeping and accidents: a content analysis of incident at sea reports

The unique profession of seafaring involves rest and sleep in a 24-h-a-day work environment that usually involves time-zone crossings, noise, heat, cold and motion. Sleep under such conditions is often difficult to obtain, and sleeping and sleep loss are often related to fatigue and contributory to accidents. This study aims to determine how accident investigators report sleep in Incident at Sea Reports and subsequently analyse the relationships between sleep, fatigue and accidents in these reports.The full text of 44 Incident at Sea Reports was coded and analysed using NUDIST software. This sample included collisions and groundings reported since 1991, where significant human factors contributed to the incident. The Incident at Sea Reports were electronically searched for reference to sleep and content was indexed against parameters such as fatigue behaviours, time of day and contributing personnel. Incident at Sea Reports incorporate three levels of reference to sleep, analysis of which may associate sleeping and sleepiness with accident causation. The highest level of reference unequivocally associates either being asleep, or being sleep deprived with accidents, but not always with fatigue. At an intermediate level, reference to the conflicting pressures of work and sleep on board fishing boats and ships suggests a work environment that is not conducive to obtaining sufficient sleep, and accident investigators are usually unable to link the watchkeeping environment with fatigue as a contributing factor. At the lowest level of association, reference is made to the integrated nature of sleeping and work on board.     

Investigating systematic individual differences in sleep-deprived performance on a high-fidelity flight simulator

Laboratory research has revealed considerable systematic variability in the degree to which individuals' alertness and performance are affected by sleep deprivation. However, little is known about whether or not different populations exhibit similar levels of individual variability. In the present study, we examined individual variability in performance impairment due to sleep loss in a highly select population of militaryjet pilots. Ten active-duty F-117 pilots were deprived of sleep for 38 h and studied repeatedly in a high-fidelity flight simulator. Data were analyzed with a mixed-model ANOVA to quantify individual variability. Statistically significant, systematic individual differences in the effects of sleep deprivation were observed, even when baseline differences were accounted for. The findings suggest that highly select populations may exhibit individual differences in vulnerability to performance impairment from sleep loss just as the general population does. Thus, the scientific and operational communities' reliance on group data as opposed to individual data may entail substantial misestimation of the impact of job-related stressors on safety and performance.     

The effects of chronic sleep reduction on the performance of cognitive tasks sensitive to sleep deprivation

In four sleep loss experiments we aimed, first, to compare performance during long-term sleep reduction with performance during short-term total sleep deprivation, and second, to measure the effects of both methods of sleep loss on ability to ignore distracting irrelevant stimuli, using a finding embedded figures test (FEFT). Logical reasoning, auditory vigilance and finding embedded figures tasks were shown to be significantly sensitive to one night's sleep deprivation. However, in one sleep reduction study subjects reduced to a mean of 5.2 hours sleep per night for 4 weeks showed no performance deficits on logical reasoning. In a second sleep reduction study subjects reduced to a mean of 4.3 hours sleep per night for 4 nights, and subjects reduced to a mean of 5.3 hours sleep per night for 18 nights, showed no performance deficits on logical reasoning or auditory vigilance, despite their reports of severe increases in subjective sleepiness and reduced concentration. Both these sleep reduction groups, though, did show decrements on the FEFT, which we interpret in terms of dearousal increasing distractibility, which the sleep-reduced subjects could not overcome with effort, as they did with the other tests.     

The impact of cognitive interference on performance during prolonged sleep loss

Summary A study was conducted on the effects of off-task cognitions on performance during sleep deprivation. Subjects answered the Thought Occurrence Questionnaire, assessing their proneness to engage in off-task cognitions, and were deprived of sleep for 72 hours, during which they performed a variety of tasks including visual discrimination and three versions of a logical reasoning task in which cognitive load was varied systematically. In addition, every day subjects answered the Cognitive Interference Questionnaire, which taps off-task cognitions during the experiment. Results indicated that subjects who habitually engage in off-task cognitions performed worse during 72 hours of sleep loss than subjects who do not engage in such distracting activities. In addition, it was found that the engagement in off-task cognitions increased during the 72 hours of sleep loss and such an engagement was related to deficits in performance accuracy. The mechanisms of off-task cognitions and sleep loss underlying these effects are discussed.     

Recovery of performance during sleep following sleep deprivation in older normal and insomniac adult males

Groups of 12 normal and insomniac male subjects aged 55 to 71 yr. were sleep deprived for 64 hr. In both groups, the sleep loss was preceded by four baseline sleep nights and followed by four recovery nights. Reaction time, immediate recall, sleepiness, and body temperature were measured at approximately 2300, 0115, 0330, 0530, and 0800 during baseline, deprivation and recovery nights. Significant performance or mood differences were not found between the normal and insomniac males on any measure or at any testing period throughout the study. Performance of both groups declined characteristically during sleep loss while subjective sleepiness increased. As in young adults, degraded performance was restored by 8 hr. of recovery sleep. However, subjective sleepiness did not return to baseline levels until early in the second recovery night. It was concluded that chronic insomnia does not result in group performance deficits similar to those seen after chronic sleep loss; and the restorative function of sleep operates as efficiently in older insomniac subjects (who apparently have reduced need to sleep) as in older normal subjects.     

Functional Equivalence of Sleep Loss and Time on Task Effects in Sustained Attention

Research on sleep loss and vigilance both focus on declines in cognitive performance, but theoretical accounts have developed largely in parallel in these two areas. In addition, computational instantiations of theoretical accounts are rare. The current work uses computational modeling to explore whether the same mechanisms can account for the effects of both sleep loss and time on task on performance. A classic task used in the sleep deprivation literature, the Psychomotor Vigilance Test (PVT), was extended from the typical 10‐min duration to 35 min, to make the task similar in duration to traditional vigilance tasks. A computational cognitive model demonstrated that the effects of time on task in the PVT were equivalent to those observed with sleep loss. Subsequently, the same mechanisms were applied to a more traditional vigilance task—the Mackworth Clock Task—providing a good fit to existing data. This supports the hypothesis that these different types of fatigue may produce functionally equivalent declines in performance.     

Effects of noise on sleep inertia as a function of circadian placement of a one-hour nap.

The purpose of the present study was to analyse the arousing effects of noise on sleep inertia as a function of circadian placement of a one-hour nap. In a first experiment, we measured the effects of sleep inertia in a neutral acoustic environment after a one-hour nap placed either at 0100 or 0400 on response time during a spatial memory test. In a second experiment were analysed the effects of an intense continuous noise on sleep inertia. The results showed that noise produced a total abolition of sleep inertia after an early nap (0000 to 0100). This may be due to the arousing effect of noise; however, results are less clear after a late nap 0300 to 0400 as noise seems to be ineffective. This result is discussed in terms of either a function of time-of-day effect or of prior sleep intensity. Moreover, our data suggest a possible interaction of noise with partial sleep deprivation leading to a slight deleterious effect those subjects who did not sleep at all.     

The effect of one night without sleep on problem-solving and immediate recall

Summary The aim of the study was to investigate the effect of spending one night without sleep on the performance of complex cognitive tasks, such as problem-solving, in comparison with a purely short-term memory task. One type of task investigated was immediate free recall, assumed to reflect the holding capacity of the working memory. The other type of task investigated was represented by syntactical reasoning and problem-solving tasks, assumed to reflect the processing (the mental transformation of input) and monitoring capacity of the working memory. Two experiments with a repeated-measures design were performed. Experiment 1 showed a significant decline in performance as a function of sleep loss on Raven's progressive matrices, a problem-solving task. No other main effect of sleep loss was found. Experiment 2 had a different order between tasks than Experiment 1 and the time without sleep was increased. A number-series induction task was also used in Experiment 2. A significant, negative effect of sleep loss in performance on Raven's progressive matrices was found in Experiment 2. The effects of sleep loss on the other tasks were nonsignificant. It is suggested that Raven's progressive-matrices task reflects the ability to monitor encoding operations (selective attention) and to monitor mental computations.     

The effects of sleep deprivation and incentives on human performance

Summary This study explores whether KR (knowledge of results) and reward compensate for the negative joint effects of sleep deprivation and signal degradation in a choice-reaction task. The negative effect of signal degradation on performance was aggravated by sleep loss and time-on-task, whereas KR improved performance, especially when signals were degraded. Reward changed the effects of time-on-task owing to lack of sleep. Performance was also improved by a brief task interruption after 30 minutes' work, with 5 more minutes to go. These results can be interpreted in terms of the performance model of Sanders (1983), which links energetic mechanisms to stages of information processing. A lack of energetic supply from the arousal mechanism to perceptual processing, induced by signal degradation, sleep deprivation, and time-on-task, was effectively counteracted by KR: KR enables the mobilization of effort to compensate for this lack of arousal. The relation between reward and KR is not yet clear. The interruption effect suggests that the influence of time-on-task is not due to loss of arousal, but causes a reallocation of resources by effort.     

Effects of sleep loss on confidence-accuracy relationships for reasoning and eyewitness memory

Participants (n = 48) deprived of sleep for 29-50 hr, in comparison with controls (n = 45), underestimated their performance on logical reasoning and Raven's matrices. Such caution may ameliorate adverse practical consequences of sleep loss. In contrast, although sleep loss participants were more suggestible on the Gudjonsson Suggestibility Scale (G. H. Gudjonsson, 1984, 1987), they maintained confidence in their suggestible responses and were inaccurate when responding with the highest rating of confidence. This indicates that the increased suggestibility is internalized and is due to a cognitive deficit rather than to compliance. Eyewitness confidence-accuracy correlations were low but usually significant and were lowest after 47-50 hr of sleep loss. Repetition of leading questions led to increases in confidence for suggestible responses (with no interaction with sleep loss) but not for nonsuggestible responses, indicating a problem for jurors' evaluations of practiced testimony.     

Effects of sleep deprivation on executive functioning,cognitive abilities,metacognitive confidence,and decision making

Performance on many decision‐making tasks is underpinned by metacognitive monitoring, cognitive abilities, and executive functioning. Fatigue‐inducing conditions, such as sleep loss, compromise these factors, leading to decline in decision performance. Using a 40‐hr sleep deprivation protocol, we examined these factors and the resulting decision performance. Thirteen Australian Army male volunteers (aged 20–30 years) were tested at multiple time points on psychomotor vigilance, inhibitory control, task switching, working memory, short‐term memory, fluid intelligence, and decision accuracy and confidence in a medical diagnosis‐making test. Assessment took place in the morning and night over two consecutive days, during which participants were kept awake. Consistent with previous work, cognitive performance declined after a night without sleep. Extending previous findings, self‐regulation and self‐monitoring suffered significantly greater declines immediately after the sleepless night. These results indicate that the known decline in complex decision‐making performance under fatigue‐inducing conditions might be facilitated by metacognitive rather than cognitive mechanisms.     

The effects of progressive sleep loss on a lexical decision task: Response lapses and response accuracy

A lexical decision task was used in a paradigm testing the effects of sleep loss and fatigue on performance during a 72-h period of sleep deprivation. The data were partitioned into categories of response lapses, response accuracy, and the signal detection measures of discriminability (d’) and bias (β). Response lapses increased as a function of sleep loss and were fitted best by a composite equation with a major linear component and a minor rhythmic component. Response accuracy decreased as a function of sleep loss, with the rate of decrease being greater for nonwords than for words. Although d’ was higher for right visual field (RVF), it decreased for both fields almost linearly as a function of sleep deprivation. The rate of decrease for RVF stimulation was greater than for left visual field (LVF) stimulation, β did not change monotonically as a function of sleep loss, but showed strong circadian rhythmicity, indicating that it was not differentially affected by sleep loss per se.     

The Effects of Exercise as a Countermeasure for Fatigue in Sleep-Deprived Aviators

This study examined the effectiveness of exercise for sustaining performance despite moderate amounts of sleep. Twelve volunteers engaged in 10-min bouts of exercise during one 40-hr period of sleep deprivation and rested for an equivalent amount of time during a 2nd period. Participants were more alert immediately following exercise, as evidenced by longer sleep latencies, than after the resting, control condition. However, electroencephalogram data collected 50 min following exercise or rest showed that exercise facilitated increases in slow-wave activity, signs of decreased alertness. Cognitive deficits and slowed reaction times associated with sleep loss were equivalent in both conditions. The results from this study suggest that short bouts of exercise may ameliorate some of the increases in sleepiness and fatigue associated with sleep loss for a short period of time but are not likely to prevent performance decrements. In addition, less than 1 hr following exercise, significant increases in fatigue and sleepiness may occur.     

What drives sleep-dependent memory consolidation: Greater gain or less loss?

When memory is tested after a delay, performance is typically better if the retention interval includes sleep. However, it is unclear what accounts for this well-established effect. It is possible that sleep enhances the retrieval of information, but it is also possible that sleep protects against memory loss that normally occurs during waking activity. We developed a new research approach to investigate these possibilities. Participants learned a list of paired-associate items and were tested on the items after a 12-h interval that included waking or sleep. We analyzed the number of items gained versus the number of items lost across time. The sleep condition showed more items gained and fewer items lost than did the wake condition. Furthermore, the difference between the conditions (favoring sleep) in lost items was greater than the difference in gain, suggesting that loss prevention may primarily account for the effect of sleep on declarative memory consolidation. This finding may serve as an empirical constraint on theories of memory consolidation.