Vigilance Tasks: Unpleasant, Mentally Demanding, and Stressful Even When Time Flies.

OBJECTIVE: To determine whether perceived time progression (PTP) moderates participants' negative reactions to vigilance tasks. BACKGROUND: Vigilance tasks are rated by participants to be unenjoyable and as having high levels of workload and stress. Based on the adage, "You are having fun when time flies," we tested the possibility that accelerating PTP might reduce these negative experiences. METHOD: Two studies were performed, involving a long 30-min and a short 12-min vigil. We manipulated participants' PTP by creating a mismatch between their expectations about how long they would perform the task and the actual time that they were engaged. RESULTS: PTP was significantly faster for participants who were led to expect that the vigilance task would last longer than it did relative to those led to expect that task duration would be shorter than it actually was and for controls for whom task duration was equal to the expected duration. However, accelerating PTP had no effect in either experiment on undesirable reactions to the vigilance tasks. Participants uniformly rated both tasks as unenjoyable, as having a high level of workload, and as stressful. Apparently, vigilance isn't fun even when time flies. CONCLUSION: Our findings greatly underscore the depth to which negative subjective reactions are embedded in the nature of vigilance tasks and therefore that these tasks can have potentially serious costs to participants in terms of health, safety, and productivity. APPLICATION: These costs must be considered at the operational level.

Training Techniques for Visual Search in Complex Task Environments.

OBJECTIVE: The goal for this study was to evaluate several visual search training techniques in an unmanned aerial vehicle (UAV) simulated task environment. BACKGROUND: Operators controlling remote unmanned vehicles often must perform complex visual search tasks (e.g., target search). These tasks may pose substantial demands on the operator due to various environmental factors. Visual search training may reduce errors and mitigate stress, but the most effective form of training has not been determined. METHODS: Participants were assigned to one of four training conditions: target, cue, visual scanning, or control. After the training, the effectiveness of the training techniques was tested during a 30-minute simulated UAV flight. A secondary task manipulation was included to further simulate the demands of a realistic UAV control and target search task. Subjective stress and fatigue were also assessed. RESULTS: Target training produced superior target search performances in more hits and fewer false alarms (FAs) when compared to the control condition. The visual scanning and cue trainings were moderately effective. Only target training performance was vulnerable to the secondary task load. The task was stressful, but training did not mitigate stress response. CONCLUSION: Training participants on the target and the cue appearance as well as active scanning of the visual field is promising for promoting effective target search for this simulated UAV environment. APPLICATION: These training techniques could be used in preparation for intelligence, surveillance, and reconnaissance (ISR) missions that involve target search, especially where target appearance change is likely.

The Neuroergonomics of Vigilance.

OBJECTIVE: The aim of this study was to examine the effects of uncertainty about where in the field of view critical signals for detection appear during a vigilance task (spatial uncertainty) on cerebral blood flow velocity (CBFV) and oculomotor fatigue. BACKGROUND: Neuroergonomics is a dimension of human factors founded by Raja Parasuraman that studies brain functions underlying performance at work. Neuroergonomic studies have shown that observers in vigilance tasks lose information-processing resources over time and experience oculomotor fatigue as indexed by a temporal decline in CBFV and elevation in eye closure as reflected in the PERCLOS metric. Because spatial uncertainty increases an observer's need for visual scanning relative to a spatial certainty condition, it was anticipated that spatial uncertainty would result in a greater temporal decline in CBFV and increased eye closure in a vigilance session. METHOD: Observers performed a simulated unmanned aerial vehicle (UAV) control task wherein collision flight paths were the events to be detected. UAV images could appear at random in any one of five locations on the controller's display (spatial uncertainty) or only in a fixed location (spatial certainty). RESULTS: Signal detection was poorer in the spatial-uncertain relative to the certain condition, and predictions regarding CBFV and eye closure were confirmed. CONCLUSION: Vigilance tasks involving spatial uncertainty are more neurophysiologically taxing than those in which spatial uncertainty is not a factor. APPLICATION: The neuroergonomic approach helps in understanding the effects of psychophysical factors in vigilance and to signify when performance aiding is needed.

Between Two Worlds.

OBJECTIVE: To provide an evaluative overview of the life and contributions of Raja Parasuraman. BACKGROUND: From his earliest contributions in clarifying and explaining the problematic area of vigilance to his most recent interdisciplinary advances in understanding how genotype relates to behavior in complex technical environments, Raja Parasuraman was a giant of human factors and ergonomics. Our present exposition articulates and recounts his many contributions to our science and to science in general beyond the confines of our own discipline. METHOD: We use the history of scientific contributions, biographical analysis, and reported personal experience to accomplish our overall assessment of the man and his work. RESULTS: We conclude that Parasuraman's contributions were unique, substantive, and seminal, and will continue to influence our science for many years to come. APPLICATION: This work will serve as a record for those to come who look to make significant contributions to the goals, aims, and aspirations that we set ourselves in human factors and ergonomics in seeking to improve the human condition.

Task Engagement and Attentional Resources.

OBJECTIVE: Two studies tested multivariate models of relationships between subjective task engagement and vigilance. The second study included a stress factor (cold infection). Modeling tested relationships between latent factors for task engagement and vigilance, and the role of engagement in mediating effects of cold infection. BACKGROUND: Raja Parasuraman's research on vigilance identified several key issues, including the roles of task factors, arousal processes, and individual differences, within the framework of resource theory. Task engagement is positively correlated with performance on various attentional tasks and may serve as a marker for resource availability. METHOD: In the first study, 229 participants performed simultaneous and successive vigilance tasks. In the second study, 204 participants performed a vigilance task and a variable-foreperiod simple reaction-time task on two separate days. On the second day, 96 participants performed while infected with a naturally occurring common cold. Task engagement was assessed in both studies. RESULTS: In both studies, vigilance decrement in hit rate was observed, and task performance led to loss of task engagement. Cold infection also depressed both vigilance and engagement. Fitting structural equation models indicated that simultaneous and successive tasks should be represented by separate latent factors (Study 1), and task engagement fully mediated the impact of cold infection on vigilance but not reaction time (Study 2). CONCLUSIONS: Modeling individual differences in task engagement elucidates the role of resources in vigilance and underscores the relevance of Parasuraman's vision of the field. APPLICATION: Assessment of task engagement may support diagnostic monitoring of operators performing tasks requiring vigilance.

The Independence and Interdependence of Coacting Observers in Regard to Performance Efficiency, Workload, and Stress in a Vigilance Task.

OBJECTIVE: We investigated performance, workload, and stress in groups of paired observers who performed a vigilance task in a coactive (independent) manner. BACKGROUND: Previous studies have demonstrated that groups of coactive observers detect more signals in a vigilance task than observers working alone. Therefore, the use of such groups might be effective in enhancing signal detection in operational situations. However, concern over appearing less competent than one's cohort might induce elevated levels of workload and stress in coactive group members and thereby undermine group performance benefits. Accordingly, we performed the initial experiment comparing workload and stress in observers who performed a vigilance task coactively with those of observers who performed the vigilance task alone. METHOD: Observers monitored a video display for collision flight paths in a simulated unmanned aerial vehicle control task. Self-reports of workload and stress were secured via the NASA-Task Load Index and the Dundee Stress State Questionnaire, respectively. RESULTS: Groups of coactive observers detected significantly more signals than did single observers. Coacting observers did not differ significantly from those operating by themselves in terms of workload but did in regard to stress; posttask distress was significantly lower for coacting than for single observers. CONCLUSION: Performing a visual vigilance task in a coactive manner with another observer does not elevate workload above that of observers working alone and serves to attenuate the stress associated with vigilance task performance. APPLICATION: The use of coacting observers could be an effective vehicle for enhancing performance efficiency in operational vigilance.

Effects of Stereoscopic Depth on Vigilance Performance and Cerebral Hemodynamics.

OBJECTIVE: We tested the possibility that monitoring a display wherein critical signals for detection were defined by a stereoscopic three-dimensional (3-D) image might be more resistant to the vigilance decrement, and to temporal declines in cerebral blood flow velocity (CBFV), than monitoring a display featuring a customary two-dimensional (2-D) image. BACKGROUND: Hancock has asserted that vigilance studies typically employ stimuli for detection that do not exemplify those that occur in the natural world. As a result, human performance is suboptimal. From this perspective, tasks that better approximate perception in natural environments should enhance performance efficiency. To test that possibility, we made use of stereopsis, an important means by which observers interact with their everyday surroundings. METHOD: Observers monitored a circular display in which a vertical line was embedded. Critical signals for detection in a 2-D condition were instances in which the line was rotated clockwise from vertical. In a 3-D condition, critical signals were cases in which the line appeared to move outward toward the observer. RESULTS: The overall level of signal detection and the stability of detection over time were greater when observers monitored for 3-D changes in target depth compared to 2-D changes in target orientation. However, the 3-D display did not retard the temporal decline in CBFV. CONCLUSION: These results provide the initial demonstration that 3-D displays can enhance performance in vigilance tasks. APPLICATION: The use of 3-D displays may be productive in augmenting system reliability when operator vigilance is vital.

The sustained attention to response task (SART) does not promote mindlessness during vigilance performance.

OBJECTIVE: In this study, we evaluated the validity of the Sustained Attention to Response Task (SART) as a means for promoting mindlessness in vigilance performance. BACKGROUND: Vigilance tasks typically require observers to respond to critical signals and to withhold responding to neutral events. The SART features the opposite response requirements, which supposedly leads it to promote a mindless, non-thoughtful approach to the vigilance task To test that notion, we compared the SART to the traditional vigilance format (TVF) in terms of diagnostic accuracy assessed through decision theory measures of positive and negative predictive power (PPP and NPP), perceived mental workload indexed by the Multiple Resource Questionnaire, and oculomotor activity reflected in the Nearest Neighbor Index and fixation dwell times. METHOD: Observers in TVF and SART conditions monitored a video display for collision flight paths in a simulated air traffic control task. RESULTS: Diagnostic accuracy in terms of NPP was high in both format conditions. While PPP was poorer in the SART than in the TVF, that result could be accounted for by a loss of motor control rather than a lack of mindfulness. Identical high levels of workload were generated by the TVF and SART tasks, and observers in both conditions showed similar dynamic scanning of the visual scene. CONCLUSION: The data indicate that the SART is not an engine of mindlessness. APPLICATION: The results challenge the widespread use of the SART to support a model in which mindlessness is considered to be the principal root of detection failures in vigilance.

Predicting battlefield vigilance: a multivariate approach to assessment of attentional resources.

Technological innovation increasingly requires operators in various applied settings to maintain vigilance for extended periods. However, standard psychometric tests typically predict less than 10% of performance variance. The present study (N = 462) aimed to apply the resource theory of sustained attention to construct a multivariate test battery for predicting battlefield vigilance. The battery included cognitive ability tests, a high-workload short vigilance task and subjective measures of stress response. Four versions of a 60- min simulated military battlefield monitoring task were constructed to represent different operational requirements. The test battery predicted 24-44% of criterion variance, depending on task version, suggesting that it may identify vigilant operators in military and other applied contexts. A multiple-groups path analysis showed that relationships between ability and vigilance were moderated by working memory demands. Findings are consistent with a diffuse theoretical concept of 'resources' in which performance energisation depends on multiple, loosely coupled processes.

Enhancing vigilance in operators with prefrontal cortex transcranial direct current stimulation (tDCS).

Sustained attention, often referred to as vigilance in humans, is the ability to maintain goal-directed behavior for extended periods of time and respond to intermittent targets in the environment. With greater time-on-task the ability to detect targets decreases and reaction time increases-a phenomenon termed the vigilance decrement. The purpose of this study was to examine the role of dorsolateral prefrontal cortex in the vigilance decrement. Subjects (n=19) received prefrontal transcranial direct current stimulation (tDCS) at one of two different time points during a vigilance task (early or late). The impact of tDCS was examined using measures of behavior, hemispheric blood flow velocity, and regional blood oxygenation relative to sham stimulation. In the sham condition greater time-on-task was accompanied by fewer target detections and slower reaction times, indicating a vigilance decrement, and decreased blood flow velocity. tDCS significantly altered baseline task-induced physiologic and behavioral changes, dependent on the time of stimulation administration and electrode configuration (determining polarity of stimulation). Compared to the sham condition, with more time-on-task blood flow velocity decreased less and cerebral oxygenation increased more in the tDCS condition. Behavioral measures showed a significant improvement in target detection performance with tDCS compared to the sham stimulation. Signal detection analysis revealed a significant change in operator discriminability and response bias with increased time-on-task, as well as interactions between time of stimulation administration and electrode configuration. Current density modeling of tDCS showed high densities in the medial prefrontal cortex and anterior cingulate cortex. These findings confirm that cerebral hemodynamic measures provide an index of resource utilization and point to the central role of the frontal cortex in vigilance. Further, they suggest that modulation of the frontal cortices-and connected structures-influences the availability of vigilance resources. These findings indicate that tDCS may be well-suited to mitigate performance degradation in work settings requiring sustained attention or as a possible treatment for neurological or psychiatric disorders involving sustained attention.

Active and passive fatigue in simulated driving: discriminating styles of workload regulation and their safety impacts.

Despite the known dangers of driver fatigue, it is a difficult construct to study empirically. Different forms of task-induced fatigue may differ in their effects on driver performance and safety. Desmond and Hancock (2001) defined active and passive fatigue states that reflect different styles of workload regulation. In 2 driving simulator studies we investigated the multidimensional subjective states and safety outcomes associated with active and passive fatigue. Wind gusts were used to induce active fatigue, and full vehicle automation to induce passive fatigue. Drive duration was independently manipulated to track the development of fatigue states over time. Participants were undergraduate students. Study 1 (N = 108) focused on subjective response and associated cognitive stress processes, while Study 2 (N = 168) tested fatigue effects on vehicle control and alertness. In both studies the 2 fatigue manipulations produced different patterns of subjective response reflecting different styles of workload regulation, appraisal, and coping. Active fatigue was associated with distress, overload, and heightened coping efforts, whereas passive fatigue corresponded to large-magnitude declines in task engagement, cognitive underload, and reduced challenge appraisal. Study 2 showed that only passive fatigue reduced alertness, operationalized as speed of braking and steering responses to an emergency event. Passive fatigue also increased crash probability, but did not affect a measure of vehicle control. Findings support theories that see fatigue as an outcome of strategies for managing workload. The distinction between active and passive fatigue is important for assessment of fatigue and for evaluating automated driving systems which may induce dangerous levels of passive fatigue.

Event-related cerebral hemodynamics reveal target-specific resource allocation for both "go" and "no-go" response-based vigilance tasks.

Transcranial Doppler sonography was used to measure cerebral blood flow velocity (CBFV) in the right and left cerebral hemispheres during the performance of a 50-min visual vigilance session. Observers monitored a simulated flight of unmanned aerial vehicles for cases in which one of the vehicles was flying in an inappropriate direction relative to its cohorts. Two types of vigilance tasks were employed: a traditional task in which observers made button press ("go") responses to critical signals, and a modification of the traditional task called the Sustained Attention to Response Task (SART) in which "go" responses acknowledged nonsignal events and response withholding ("no-go") signified signal detection. Signal detections and global CBFV scores declined over time. In addition, fine-grained event-related analyses revealed that the detection of signals was accompanied by an elevation of CBFV that was not present with missed signals. As was the case with the global scores, the magnitude of the transient CBFV increments associated with signal detection also declined over time, and these findings were independent of task type. The results support the view of CBFV as an index of the cognitive evaluation of stimulus significance, and a resource model of vigilance in which the need for continuous attention produces a depletion of information-processing assets that are not replenished as the task progresses. Further, temporal declines in the magnitude of event-related CBFV in response to critical signals only is evidence that the decrement function in vigilance is due to attentional processing and not specific task elements such as the required response format.

Viewing the workload of vigilance through the lenses of the NASA-TLX and the MRQ.

OBJECTIVE: The aim of this study was to compare the effectiveness of a new index of perceived mental workload, the Multiple Resource Questionnaire (MRQ), with the standard measure of workload used in the study of vigilance, the NASA Task Load Index (NASA-TLX). BACKGROUND: The NASA-TLX has been used extensively to demonstrate that vigilance tasks impose a high level of workload on observers. However, this instrument does not specify the information-processing resources needed for task performance. The MRQ offers a tool to measure the workload associated with vigilance assignments in which such resources can be identified. METHOD: Two experiments were performed in which factors known to influence task demand were varied. Included were the detection of stimulus presence or absence, detecting critical signals by means of successive-type (absolute judgment) and simultaneous-type (comparative judgment) discriminations, and operating under multitask vs. single-task conditions. RESULTS: The MRQ paralleled the NASA-TLX in showing that vigilance tasks generally induce high levels of workload and that workload scores are greater in detecting stimulus absence than presence and in making successive as compared to simultaneous-type discriminations. Additionally, the MRQ was more effective than the NASA-TLX in reflecting higher workload in the context of multitask than in single-task conditions. The resource profiles obtained with MRQ fit well with the nature of the vigilance tasks employed, testifying to the scale's content validity. CONCLUSION: The MRQ may be a meaningful addition to the NASA-TLX for measuring the workload of vigilance assignments. APPLICATION: By uncovering knowledge representation associated with different tasks, the MRQ may aid in designing operational vigilance displays.

Mental workload and stress perceived by novice operators in the laparoscopic and robotic minimally invasive surgical interfaces.

BACKGROUND AND PURPOSE: High levels of mental workload and stress are experienced by surgeons in the laparoscopic environment. The da Vinci(®) surgical robot was developed to provide surgeons a more user-friendly interface while maintaining the patient benefits associated with laparoscopy. This study examined whether the da Vinci robot reduces mental workload and stress in novice medical students. A detailed understanding of trainees' mental workload and mental stress experiences can aid in the development of training programs that are aimed at facilitating the acquisition of laparoscopic and robotic surgery skills. MATERIALS AND METHODS: Fifteen novice first-year medical students performed a standard peg-transfer task at a laparoscopic simulator and the da Vinci Surgical System. Mental workload and stress were assessed with the Multiple Resources Questionnaire (MRQ) and the Dundee Stress State Questionnaire (DSSQ), respectively. RESULTS: Students' mental workload profiles were identical with the two surgical systems and replicated previous MRQ results reported with the laparoscopic system showing high levels of workload. Students experienced a better stress profile with the robotic system, however, when compared wih the laparoscopic system. CONCLUSION: Our study shows that novice medical students perceive less stress when working with the robotic surgical interface than with the laparoscopic surgery interface. The MRQ and the DSSQ are valuable tools for identifying mental workload and mental stress in the laparoscopic and robotic surgery environments. This information may be useful for facilitating the acquisition of laparoscopic and robotic surgery skills.

Symposium: Neuroergonomics, technology, and cognition.

This symposium describes collaborative research on neuroergonomics, technology, and cognition being conducted at George Mason University and the US Air Force Research Laboratory (AFRL) as part of the Center of Excellence in Neuroergonomics, Technology, and Cognition (CENTEC). Six presentations describe the latest developments in neuroergonomics research conducted by CENTEC scientists. The individual papers cover studies of: (1) adaptive learning systems; (2) neurobehavioral synchronicity during team performance; (3) genetics and individual differences in decision making; (4) vigilance and mindlessness; (5) interruptions and multi-tasking; and (6) development of a simulation capability that integrates measures across these domains and levels of analysis.

Stress training improves performance during a stressful flight.

OBJECTIVE: This study investigated whether stress training introduced during the acquisition of simulator-based flight skills enhances pilot performance during subsequent stressful flight operations in an actual aircraft. BACKGROUND: Despite knowledge that preconditions to aircraft accidents can be strongly influenced by pilot stress, little is known about the effectiveness of stress training and how it transfers to operational flight settings. METHOD: For this study, 30 participants with no flying experience were assigned at random to a stress-trained treatment group or a control group. Stress training consisted of systematic pairing of skill acquisition in a flight simulator with stress coping mechanisms in the presence of a cold pressor. Control participants received identical flight skill acquisition training but without stress training. Participants then performed a stressful flying task in a Piper Archer aircraft. RESULTS: Stress-trained research participants flew the aircraft more smoothly, as recorded by aircraft telemetry data, and generally better, as recorded by flight instructor evaluations, than did control participants. CONCLUSIONS: Introducing stress coping mechanisms during flight training improved performance in a stressful flying task. APPLICATION: The results of this study indicate that stress training during the acquisition of flight skills may serve to enhance pilot performance in stressful operational flight and, therefore, might mitigate the contribution of pilot stress to aircraft mishaps.

Task engagement, cerebral blood flow velocity, and diagnostic monitoring for sustained attention.

Loss of vigilance may lead to impaired performance in various applied settings including military operations, transportation, and industrial inspection. Individuals differ considerably in sustained attention, but individual differences in vigilance have proven to be hard to predict. The dependence of vigilance on workload factors is consistent with a resource model of sustained attention. Thus, measures of attentional resource availability may predict the operator's subsequent vigilance performance. In this study, we investigated whether a diagnostic battery of measures of response to a cognitive challenge would predict subsequent sustained attention. Measures that may relate to the mobilization of resources in response to task demands include subjective task engagement and coping, and a novel psychophysiological index, cerebral bloodflow velocity (CBFV). A two-phase design was used. First, participants were exposed to a challenging battery of short tasks that elevated CBFV. Second, participants performed a 36-min vigilance task. Two subgroups of participants performed either a sensory vigilance (N = 187) or a cognitive vigilance (N = 107) task. Measures of task engagement, coping, and CBFV response to the short task battery were compared as predictors of subsequent vigilance. Both subjective and CBFV indices of energization predicted sensory and cognitive vigilance, consistent with resource theory. Structural equation modeling was used to develop a latent factor model of influences on sustained attention. It is concluded that measures of resources, conceptualized as multiple energization processes, are potentially useful for diagnostic monitoring in applied settings. Use of a diagnostic task battery in military and transportation settings is discussed, along with some potential limitations on validity of the diagnostic test.

Cerebral lateralization of vigilance: a function of task difficulty.

Functional near infrared spectroscopy (fNIRS) measures of cerebral oxygenation levels were collected from participants performing difficult and easy versions of a 12 min vigilance task and for controls who merely watched the displays without a work imperative. For the active participants, the fNIRS measurements in both vigilance tasks showed higher levels of cerebral activity than was present in the case of the no-work controls. In the easier task, greater activation was found in the right than in the left cerebral hemisphere, matching previous results indicating right hemisphere dominance for vigilance. However, for the more difficult task, this laterality difference was not found, instead activation was bilateral. Unilateral hemispheric activation in vigilance may be a result of employing relatively easy/simple tasks, not vigilance per se.

A transcranial Doppler sonography study of shoot/don't-shoot responding.

The purpose of this study was to examine the relationship between changes in cerebral blood-flow velocity and performance on a speeded shoot/don't-shoot task. Brain activity as indicated by cerebral blood-flow velocity (hemovelocity) was recorded using the transcranial Doppler ultrasonography. A shoot/don't-shoot decision-making task presented participants with threat/nonthreat stimuli in the form of bull's-eye images of various colors. Participants were required to shoot threat targets using a laser-modified handgun. Results support a vigilance decrement in both the performance measures and hemovelocity. Performance, as measured by reaction time, number of hits, and marksmanship, decreased across the length of the vigil. Hemovelocity slowed across the left and right hemispheres as the task progressed, and hemovelocity was slower in the right hemisphere than in the left hemisphere.

Effects of sensory modality on cerebral blood flow velocity during vigilance.

Transcranial Doppler sonography was used to measure cerebral blood flow velocity (hemovelocity, CBFV) from the left and right middle cerebral arteries during the performance of 40-min auditory and visual vigilance tasks. Reductions in stimulus duration were the critical signals for detection in both tasks, which were equated for stimulus salience and discrimination difficulty. Signal detection responses (correct detections and false alarms) and CBFV declined significantly over time in a linear manner for both modalities. In addition, the overall level of CBFV and the temporal decline in this measure were greater in the right than the left cerebral hemisphere. The results are consistent with the view that a right hemispheric system is involved in the functional control of vigilance and that this system operates in a similar manner in the auditory and visual channels.