Joseph V. Baranski

Modafinil, d‐amphetamine and placebo during 64 hours of sustained mental work. I. Effects on mood, fatigue, cognitive performance and body temperature

SUMMARY  Modafinil is an alerting substance that is considered safer than amphetamine with fewer side effects. Although modafinil has been used successfully to treat narcolepsy, relatively little is known about its ability to ameliorate fatigue and declines in mental performance due to sleep deprivation (SD) in a normal population. Forty‐one military subjects received either 300 mg of modafinil, 20 mg of d‐amphetamine, or placebo on 3 separate occasions during 64 hours of continuous cognitive work and sleep loss. Three drug treatments were given: at 23.30 hours and 05.30 hours during the first and second SD nights, respectively, and once at 15.30 hours during the third day of continuous work. Subjective estimates of mood, fatigue and sleepiness, as well as objective measures of reaction time, logical reasoning and short‐term memory clearly showed better performance with both modafinil and amphetamine relative to placebo. Both modafinil and amphetamine maintained or increased body temperature compared to the natural circadian cycle observed in the placebo group. Also, from subject debriefs at the end of the study, modafinil elicited fewer side‐effects than amphetamine, although more than the placebo group. Modafinil appears to be a good alternative to amphetamine for counteracting the debilitating mood and cognitive effects of sleep loss during sustained operations.

Self-monitoring cognitive performance during sleep deprivation: effects of modafinil, d-amphetamine and placebo

Self‐monitoring refers to the ability to assess accurately ones own performance in a specific environment. The present study investigated the effects of the stimulating drugs modafinil (300 mg) and d‐amphetamine (20 mg) on the ability to self‐monitor cognitive performance during 64 h of sleep deprivation (SD) and sustained mental work. Two cognitive tasks were investigated: a visual (perceptual) judgment task and a complex mental addition task. Subjects in the placebo condition displayed marked circadian and SD effects on cognitive task performance but their self‐monitoring was substantively undisturbed by SD. Subjects performing under the influence of d‐amphetamine likewise displayed highly proficient self‐monitoring throughout the SD period. In contrast, modafinil had a disruptive effect on self‐monitoring, inducing a reliable «overconfidence» effect (i.e. an overestimation of actual cognitive performance), which was particularly marked 2–4 h post‐dose. Although modafinil has proven to be a safe and effective countermeasure to the effects of extensive SD on cognitive task performance, we encourage a more comprehensive understanding of the relation between its subjective and performance enhancing effects before the drug is recommended as a viable fatigue countermeasure.

Judging confidence influences decision processing in comparative judgments.

Current theories of confidence in human judgment assume that confidence and the decision it is based on are inextricably tied to the same process (decisional locus theories) or that confidence processing begins only once the primary decision has been completed (postdecisional locus theories). In the absence of auxiliary assumptions, however, neither class of theory permits the judgment of confidence to affect primary decision processing. In the present study, we examined the effect of rendering confidence judgments on the properties of the decision process in a sensory discrimination task. An examination of the properties of the time taken to determine confidence (i.e., the time taken to render the judgment of confidence) revealed clear evidence of postdecisional confidence processing. Concomitantly, the requirement of confidence judgments was found to substantially increase decisional response times, suggesting that some confidence processing occurs during the primary decision process. We discuss the implications of these findings for contemporary models of confidence in human judgment.

On the ability to self-monitor cognitive performance during sleep deprivation: a calibration study

SUMMARY  The antagonistic effects of extensive sleep deprivation (SD) on human cognitive performance are well documented. However, one aspect of human performance that has not been investigated with respect to its susceptibility to SD is the ‘metacognitive’ ability to self‐monitor overt performance. In the present study, 16 male subjects participated in an experiment requiring sustained cognitive work during a three day period. One of the cognitive tasks required the mental addition of rapidly presented numbers. On each trial, subjects reported the sum and then provided a subjective confidence rating to indicate the degree of certainty in their response. As expected, performance on the sequential addition task deteriorated with increasing fatigue and returned to baseline following a recovery sleep. However, calibration analyses, which quantify a number of properties of the relationship between subjective and overt performance, revealed that the correlation between confidence and performance (calibration), the ability to differentiate correct from incorrect judgments (resolution), and validity of subjective ‘certainty’, were all unaffected by SD. Hence, in the absence of external feedback from the environment, people have access to fairly reliable internal feedback about their performance during periods of sustained and vigilant cognitive activity.

Effects of Sleep Loss on Team Decision Making: Motivational Loss or Motivational Gain?:

Objective: To examine the effects of 30 hr of sleep loss and continuous cognitive work on performance in a distributed team decision-making environment. Background: To date, only a few studies have examined the effect of sleep loss on distributed team performance, and only one other to our knowledge has examined the relationship between sleep loss and social-motivational aspects of teams (Hoeksema-van Orden, Gaillard, & Buunk, 1998). Method: Sixteen teams participated; each comprised 4 members. Three team members made threat assessments on a military surveillance task and then forwarded their judgments electronically to a team leader, who made a final assessment on behalf of the team. Results: Sleep loss had an antagonistic effect on team decision-making accuracy and decision time. However, the performance loss associated with fatigue attributable to sleep loss was mediated by being part of a team, as compared with performing the same task individually — that is, we found evidence of a “motivational gain” effect in these sleepy teams. We compare these results with those of Hoeksema-van Orden et al. (1998), who found clear evidence of a “social loafing” effect in sleepy teams. Conclusion: The divergent results are discussed in the context of the collective effort model (Karau & Williams, 1993) and are attributable in part to a difference between independent and interdependent team tasks. Application: The issues and findings have implications for a wide range of distributed, collaborative work environments, such as military network-enabled operations.

Fatigue, Sleep Loss, and Confidence in Judgment.

Sixty-four adults participated in a study examining the accuracy of metacognitive judgments during 28 hr of sleep deprivation (SD) and continuous cognitive work. Three tasks were studied (perceptual comparison, general knowledge, and mental addition), collectively spanning a range of cognitive abilities and levels of susceptibility to SD. Subjective and objective measures of sleepiness confirmed the expected patterns of increasing fatigue with SD. Participants displayed differing levels of metacognitive abilities across tasks, but traditional indices of the confidence-accuracy relation (i.e., calibration, resolution, over- and underconfidence), as well as the accuracy of pre- and posttask estimates of performance, remained stable over the SD period. The findings suggest that people can accurately assess their own cognitive performance when deprived of 1 night of sleep and that this ability need not be based on subjective estimates of sleepiness. The implications and limitations of the study are discussed and directions for future research are proposed.

Effects of Modafinil on Cognitive Performance During 40 Hr of Sleep Deprivation in a Warm Environment

This study examined the effect of the psychostimulant modafinil on cognitive performance during 40 hr of sleep deprivation in a warm environment. Five men were randomly assigned to a modafinil (3 × 100 mg/24 hr) and a placebo trial on consecutive weeks, with a 5-day intervening “wash-out” period. Each trial involved a thermoneutral control day (outside of the climatic chamber) followed by a 40-hr sleep deprivation period in a climatic chamber at 30°C with 50% relative humidity. Ten cognitive testing sessions were conducted on each trial; each session lasted approximately 45 min, and they occurred at 6-hr intervals. The task battery included subjective assessments of mood, fatigue, and motivation and cognitive assessments of serial reaction time, logical reasoning (logical reasoning task [LRT]), visual comparison (CMP), mental addition (ADD), vigilance (detection of repeated numbers [DRN]), and multitasking. In addition, for 4 of the cognitive tasks that permitted a quantitative index of response accuracy (i.e., LRT, CMP, DRN, and ADD), participants provided estimates of their performance before and after each session to permit an evaluation of the extent to which they could accurately self-monitor their own cognitive abilities. The findings revealed that (a) despite significant increases in core body temperature, cognitive performance was largely unaffected by the warm environment per se; (b) sleep loss induced a general reduction in cognitive performance that was largely but not completely eliminated by modafinil; and (c) participants were able to accurately self-monitor their own cognitive capabilities during both the placebo and modafinil trials. In this article, we discuss the potential utility of modafinil in sustained military operations and the general implications of these findings for Hancocks (1986) theory of sustained attention under thermal stress.

Adaptive decision processes in perceptual comparisons: effects of changes in the global difficulty context.

Adaptive decision processes were investigated in experiments involving an unexpected change in the global ease or difficulty of the task. Under accuracy stress, a shift from an easy to a difficult context induced a marked increase in decision time, but a shift from a difficult to an easy context did not. Under speed stress, a shift to a more difficult context induced lower accuracy and rated confidence, depending on the difficulty of the decisions. A view of caution developed in D. Vickerss (1979) accumulator theory--whereby one seeks to base decisions on more information--is compared with a view based on slow and fast guessing theory (W. M. Petrusic, 1992; W. M. Petrusic & J. V. Baranski, 1989a)--whereby one seeks to base decisions on more diagnostic information. On balance, the findings support the latter view.

Long-term memory for elementary visual percepts: Memory psychophysics of context and acquisition effects

In the first phase of each of two experiments, participants learned to associate a set of labels (i.e., consonant-vowel-consonant [CVC]) with a set of line lengths by using a paired-associate learning procedure. In the second phase of each experiment, these learned labels were used as memorial standards in the method of constant stimuli. Psychometric functions and the associated indices of discriminative performance (i.e., Weber fractions [WFs], just noticeable difference, and point of subjective equality) were then obtained for the remembered standards. In Experiment 1, WFs (i.e., the indices of memory precision) obtained with remembered standards were found to be higher (i.e., had poorer discriminability) than were WFs obtained with perceptual standards. In addition, WFs obtained with the remembered standards exhibited serial position effects (i.e., poorer discriminability for central items in the memory ensemble) and systematically varied with set size (i.e., the number of standards in the memory set), but WFs obtained with perceptual standards did not depend on serial position or set size. In Experiment 2, increasing the number of acquisition trials reduced WFs and diminished serial position effects. In addition, WFs did not vary systematically with the “physical” spacing between the standards in memory, but they did with the ordinal spacing. The results are consistent with anoisy analogue representation of remembered magnitudes, whereby central items in a memory ensemble are subject to lateral inhibition and thus reduced discriminability. Finally, presentation order effects, as defined by the classic time-order error, were observed with purely perceptual comparisons but not with comparisons involving a remembered standard. This latter finding is inconsistent with a strong form of thefunctional equivalence view of perception and memory.