Auditory vigilance task performance and cerebral hemodynamics: effects of spatial uncertainty.

The vigilance decrement, a temporal decline in detection performance, has been observed across multiple sensory modalities. Spatial uncertainty about the location of task-relevant stimuli has been demonstrated to increase the demands of vigilance and increase the severity of the vigilance decrement when attending to visual displays. The current study investigated whether spatial uncertainty also increases the severity of the vigilance decrement and task demands when an auditory display is used. Individuals monitored an auditory display to detect critical signals that were shorter in duration than non-target stimuli. These auditory stimuli were presented in either a consistent, predictable pattern that alternated sound presentation from left to right (spatial certainty) or an inconsistent, unpredictable pattern that randomly presented sounds from the left or right (spatial uncertainty). Cerebral blood flow velocity (CBFV) was measured to assess the neurophysiological demands of the task. A decline in performance and CBFV was observed in both the spatially certain and spatially uncertain conditions, suggesting that spatial auditory vigilance tasks are demanding and can result in a vigilance decrement. Spatial uncertainty resulted in a more severe vigilance decrement in correct detections compared to spatial certainty. Reduced right-hemispheric CBFV was also observed during spatial uncertainty compared to spatial certainty. Together, these results suggest that auditory spatial uncertainty hindered performance and required greater attentional demands compared to spatial certainty. These results concur with previous research showing the negative impact of spatial uncertainty in visual vigilance tasks, but the current results contrast recent research showing no effect of spatial uncertainty on tactile vigilance.

Effects of task demands on tactile vigilance.

A performance decline during sustained monitoring of unpredictable and occasional signals, the vigilance decrement, has been studied mostly in the visual and auditory modalities, but a tactile vigilance decrement also has been observed and has been associated with high perceived workload, declines in sensitivity and task engagement, and increases in distress. The primary aim of the current study was to determine whether task demands affect the vigilance decrement in the tactile modality and whether the effects are similar to those observed in the auditory and visual modalities. Participants completed a 40-min vigil in which they monitored vibrotactile stimuli generated by a tactor and had to discriminate between durations of bursts of vibrations. Task demand was varied by including low and high event rates. Although correct detections decreased over time (vigilance decrement) and sensitivity was greater for the slower event rate, there was not an interaction between period of watch and event rate. There also were no differences in workload and stress between event rates. Results indicate that mean performance in tactile vigilance tasks is negatively impacted by increases in event rate, indicating that a typical source of task demand known to affect visual and auditory vigilance also affects tactile vigilance. Results could be explained by either an underload or overload theory of the vigilance decrement.

An investigation of cardiac vagal tone over time and its relation to vigilance performance: a growth curve modeling approach.

Introduction: Research over the last couple of decades has demonstrated a relationship between psychophysiological measures, specifically cardiac functions, and cognitive performance. Regulation of the cardiac system under parasympathetic control is commonly referred to as cardiac vagal tone and is associated with the regulation of cognitive and socioemotional states. The goal of the current study was to capture the dynamic relationship between cardiac vagal tone and performance in a vigilance task. Method/Results: We implemented a longitudinal growth curve modeling approach which unveiled a relationship between cardiac vagal tone and vigilance that was non-monotonic and dependent upon each person. Discussion: The findings suggest that cardiac vagal tone may be a process-based physiological measure that further explains how the vigilance decrement manifests over time and differs across individuals. This contributes to our understanding of vigilance by modeling individual differences in cardiac vagal tone changes that occur over the course of the vigilance task.

Vigilance to Spatialized Auditory Displays: Initial Assessment of Performance and Workload.

OBJECTIVE: The present study was designed to evaluate human performance and workload associated with an auditory vigilance task that required spatial discrimination of auditory stimuli. BACKGROUND: Spatial auditory displays have been increasingly developed and implemented into settings that require vigilance toward auditory spatial discrimination and localization (e.g., collision avoidance warnings). Research has yet to determine whether a vigilance decrement could impede performance in such applications. METHOD: Participants completed a 40-minute auditory vigilance task in either a spatial discrimination condition or a temporal discrimination condition. In the spatial discrimination condition, participants differentiated sounds based on differences in spatial location. In the temporal discrimination condition, participants differentiated sounds based on differences in stimulus duration. RESULTS: Correct detections and false alarms declined during the vigilance task, and each did so at a similar rate in both conditions. The overall level of correct detections did not differ significantly between conditions, but false alarms occurred more frequently within the spatial discrimination condition than in the temporal discrimination condition. NASA-TLX ratings and pupil diameter measurements indicated no differences in workload. CONCLUSION: Results indicated that tasks requiring auditory spatial discrimination can induce a vigilance decrement; and they may result in inferior vigilance performance, compared to tasks requiring discrimination of auditory duration. APPLICATION: Vigilance decrements may impede performance and safety in settings that depend on sustained attention to spatial auditory displays. Display designers should also be aware that auditory displays that require users to discriminate differences in spatial location may result in poorer discrimination performance than non-spatial displays.

Modality Changes in Vigilance Displays: Further Evidence of Supramodal Resource Depletion in Vigilance.

OBJECTIVE: This study was designed to evaluate the effects of a modality change on vigilance performance to determine whether depletion of modality-specific resources contributes to the vigilance decrement. BACKGROUND: Resource theory accounts for the vigilance decrement by arguing that the demands of vigilance deplete limited information processing resources. Research indicates that both supramodal and modality-specific resources are involved in vigilance, but it is unclear whether the vigilance decrement is due to depletion of supramodal resources, modality-specific resources, or both. If depletion of modality-specific resources contributes to the decrement, changing the modality of a vigilance display should improve vigilance performance after a decrement. METHOD: Participants completed a 50-min vigilance task beginning in either the visual modality or the auditory modality. After 40-min, half of the participants experienced a sudden transition to the other modality; the remaining participants did not experience a modality change. RESULTS: Performance declined over time and was generally superior in the auditory modality. Changing modality from visual to auditory increased correct detections, whereas changing from auditory to visual decreased correct detections. Both types of modality change were associated with an increase in false alarms, and neither had an effect on workload or stress. CONCLUSION: Supramodal resource depletion, rather than modality-specific resource depletion, is the most likely explanation for the vigilance decrement that can be derived from resource theory. APPLICATION: Modality changes are not likely to counteract the vigilance decrement and may actually increase false alarm errors. Countermeasure development should involve identification of depleted supramodal resources.

Driver Vigilance Decrement is More Severe During Automated Driving than Manual Driving.

OBJECTIVE: The present study compared the performance, workload, and stress associated with driver vigilance in two types of vehicle: a traditional, manually operated vehicle, and a partially automated vehicle. BACKGROUND: Drivers of partially automated vehicles must monitor for hazards that constitute automation failures and the need for human intervention, but recent research indicates that a driver's ability to do so declines as a function of time. That research lacked a comparison measure of driving without vehicle automation, so it is unknown to what degree these effects are specific symptoms of monitoring the roadway during an automated drive. Drivers in manual control of their vehicle must similarly monitor for hazards and may suffer similar vigilance decrements. METHOD: Participants completed a simulated 40-minute drive while monitoring for hazards. Half of participants completed the drive with an automated driving system that maintained speed and lane position; the remaining half manually controlled the vehicle's speed and lane position. RESULTS: Driver sensitivity to hazards decreased and tendency to make false alarms increased over time in the automated control condition, but not in the manual control condition. Drivers in both conditions detected fewer hazards as the drive progressed. Ratings of workload and task-induced stress were elevated similarly in both conditions. CONCLUSION: Partially automated driving appears to uniquely impair driver vigilance by reducing the ability to discriminate between benign and dangerous events in the driving environment as the drive progresses. APPLICATION: Applied interventions should target improvements in driver sensitivity to hazardous situations that signal potential automation failures.

Optimizing aid activation in adaptive and non-adaptive aiding systems: A framework for design and validation.

Development of adaptive aids to support human performance in complex systems is a cornerstone of human factors. Research in this area has led to a diversity of ideas regarding potential activation methods. However, little guidance has been provided on how to select among aid activation methods, and this lack of guidance could hinder adaptive aid development and deployment. Within the current paper, we review available methods of aid activation and describe a process for developing and validating adaptive aiding systems. We focus on supporting system designers who wish to select the ideal aid activation method for an intended application. The process that we recommend is an empirical approach to evaluate the feasibility, costs, and benefits of various potential methods of aid activation. This methodological framework will support practitioners making critical decisions about the design of aiding systems.

Tactile Vigilance Is Stressful and Demanding.

OBJECTIVE: The primary aims of the study were to replicate the vigilance decrement in the tactile modality, examine whether a decrease in sensitivity is associated with the decrement, and determine whether tactile vigilance is stressful and demanding. BACKGROUND: When people monitor occasional and unpredictable signals for sustained durations, they experience a decline in performance known as the vigilance decrement, which has important practical consequences. Prior studies of the vigilance decrement focused primarily on visual vigilance and, to a lesser degree, on auditory vigilance. There are relatively few studies of tactile vigilance. METHOD: Participants monitored vibrotactile stimuli that were created from a tactor, for 40 min. RESULTS: Sensitivity declined, self-report ratings of distress increased, and ratings of task engagement decreased, during the vigil, and perceived workload was moderately high. CONCLUSION: Monitoring tactile signals is demanding and stressful and results in a decrement in signal detection. APPLICATION: Monitoring tactile signals may result in a decrement in tasks requiring discrimination, such as monitoring lane position with the use of rumble strips; these require discrimination between current road vibration and increased vibration when the car drifts out of its lane and crosses over the strip.

Is Physiobehavioral Monitoring Nonintrusive? An Examination of Transcranial Doppler Sonography in a Vigilance Task.

OBJECTIVE: The current study was designed to determine whether continuous, physiobehavioral monitoring via transcranial Doppler sonography (TCD) has negative effects on human performance or user state in a vigilance task. BACKGROUND: Physiobehavioral measures have been identified as a promising method of user state assessment, in part because they are thought to be relatively nonintrusive. The notion that physiobehavioral measures are nonintrusive should not be taken for granted and needs to be tested empirically. It is possible that, even though physiobehavioral measures do not require input from a user, they may still hinder performance by causing discomfort, distraction, or interfering with physical activities required for task performance. METHOD: The current study employed TCD, a common method of monitoring user vigilance. Participants completed a 40-min vigilance task. During the task, 50% wore TCD apparatus, while 50% did not. Intrusiveness was measured in terms of vigilance performance as well as workload, stress, and simulator sickness. RESULTS: Analyses revealed results that mirrored prototypical vigilance findings: performance declined over time, workload was high, distress and reported simulator sickness symptomology increased during the task, while engagement decreased. The presence or absence of TCD monitoring had no direct or interactive effects on performance or user state. CONCLUSION: TCD monitoring of user vigilance appears to be nonintrusive. APPLICATION: Findings support the recommendation that TCD should be used in research and operational settings where user vigilance is of paramount importance. More broadly, when developing and fielding physiobehavioral state measurement systems, intrusiveness should be considered and evaluated.

Driver Vigilance in Automated Vehicles: Effects of Demands on Hazard Detection Performance.

OBJECTIVE: The current study investigated driver vigilance in partially automated vehicles to determine whether increased task demands reduce a driver's ability to monitor for automation failures and whether the vigilance decrement associated with hazard detections is due to driver overload. BACKGROUND: Drivers of partially automated vehicles are expected to monitor for signs of automation failure. Previous research has shown that a driver's ability to perform this duty declines over time. One possible explanation for this vigilance decrement is that the extreme demands of vigilance causes overload and leads to depletion of limited attentional resources required for vigilance. METHOD: Participants completed a 40-min drive in a simulated partially automated vehicle and were tasked with monitoring for hazards that represented potential automation failures. Two factors were manipulated to test the impact of monitoring demands on performance: Spatial uncertainty and event rate. RESULTS: As predicted, hazard detection performance was poorer when monitoring demands were increased, and performance declined as a function of time on task. Subjective reports also indicated high workload and task-induced stress. CONCLUSION: Drivers of partially automated vehicles are impaired by the vigilance decrement and elevated task demands, meaning that safe operation becomes less likely when the demands associated with monitoring automation increase and as a drive extends in duration. This study also supports the notion that vigilance performance in partially automated vehicles is likely due to driver overload. APPLICATION: Developers of automation technologies should consider countermeasures that attenuate a driver's cognitive load when tasked with monitoring automation.

Evaluation of the Team Workload Questionnaire (TWLQ) in a Team-Choice Task.

OBJECTIVE: The present study was designed to evaluate the team workload questionnaire (TWLQ) in a task that was distinct from the task used to create it. BACKGROUND: The TWLQ was created from workload ratings generated by members of athletic sports teams. Given that such teams represent only a portion of the diversity of operational teams, we aimed to assess the generalizability of the TWLQ. METHOD: The present study applied the TWLQ in a collaborative choice task (hiring decision) to determine whether the factor structure reported in the initial publication of the scale would generalize from the execution tasks it was developed from to a disparate team task focused on consensus building. RESULTS: Confirmatory factor analysis indicated that the present data (N = 144) were a poor fit for the three-factor structure of the TWLQ. Subsequent exploratory factor analysis revealed a much more interrelated model of team workload with no clear division between the three conceptual factors described in the original validation of the TWLQ. CONCLUSION: The factor structure of the TWLQ did not generalize to the present team-choice task. APPLICATION: Given that the duties of operational teams vary, it is critical that future research examine how the conceptual structure of team workload may be altered by task type.

Driver Vigilance in Automated Vehicles: Hazard Detection Failures Are a Matter of Time.

OBJECTIVE: The primary aim of the current study was to determine whether monitoring the roadway for hazards during automated driving results in a vigilance decrement. BACKGROUND: Although automated vehicles are relatively novel, the nature of human-automation interaction within them has the classic hallmarks of a vigilance task. Drivers must maintain attention for prolonged periods of time to detect and respond to rare and unpredictable events, for example, roadway hazards that automation may be ill equipped to detect. Given the similarity with traditional vigilance tasks, we predicted that drivers of a simulated automated vehicle would demonstrate a vigilance decrement in hazard detection performance. METHOD: Participants "drove" a simulated automated vehicle for 40 minutes. During that time, their task was to monitor the roadway for roadway hazards. RESULTS: As predicted, hazard detection rate declined precipitously, and reaction times slowed as the drive progressed. Further, subjective ratings of workload and task-related stress indicated that sustained monitoring is demanding and distressing and it is a challenge to maintain task engagement. CONCLUSION: Monitoring the roadway for potential hazards during automated driving results in workload, stress, and performance decrements similar to those observed in traditional vigilance tasks. APPLICATION: To the degree that vigilance is required of automated vehicle drivers, performance errors and associated safety risks are likely to occur as a function of time on task. Vigilance should be a focal safety concern in the development of vehicle automation.

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.

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.