James L. Szalma

The vigilance decrement reflects limitations in effortful attention, not mindlessness.

Robertson, Manly, Andrade, Baddeley, and Yiend (1997) proposed that the decline in performance efficiency over time in vigilance tasks (the vigilance decrement) is characterized by “mindlessness” or a withdrawal of attentional effort from the monitoring assignment. We assessed that proposal using measures of perceived mental workload (NASA-TLX) and stress (Dundee Stress State Questionnaire). Two types of vigilance task were employed: a traditional version, wherein observers made button-press responses to signify detection of rarely occurring critical signals, and a modified version, developed by Robertson et al. to promote mindlessness via routinization, wherein button-press responses acknowledged frequently occurring neutral stimulus events and response withholding signified critical signal detection. The vigilance decrement was observed in both tasks, and both tasks generated equally elevated levels of workload and stress, the latter including cognitions relating to performance adequacy. Vigilance performance seems better characterized by effortful attention (mindfulness) than by mindlessness. Actual or potential applications of this research include procedures to reduce the information-processing demand imposed by vigilance tasks and the stress associated with such tasks.

A Meta-Analysis of Performance Response Under Thermal Stressors:

Objective: Quantify the effect of thermal stressors on human performance. Background: Most reviews of the effect of environmental stressors on human performance are qualitative. A quantitative review provides a stronger aid in advancing theory and practice. Method: Meta-analytic methods were applied to the available literature on thermal stressors and performance. A total of 291 references were collected. Forty-nine publications met the selection criteria, providing 528 effect sizes for analysis. Results: Analyses confirmed a substantial negative effect on performance associated with thermal stressors. The overall effect size for heat was comparable to that for cold. Cognitive performance was least affected by thermal stressors, whereas both psychomotor and perceptual task performance were degraded to a greater degree. Other variables were identified that moderated thermal effects. Conclusion: Results confirmed the importance of task type, exposure duration, and stressor intensity as key variables impacting how thermal conditions affect performance. Results were consistent with the theory that stress forces the individual to allocate attentional resources to appraise and cope with the threat, which reduces the capacity to process task-relevant information. This represents a maladaptive extension of the narrowing strategy, which acts to maintain stable levels of response when stress is first encountered. Application: These quantitative estimates can be used to design thermal tolerance limits for different task types. Although results indicate the necessity for further research on a variety of potentially influential factors such as acclimatization, the current summary provides effect size estimates that should be useful in respect to protecting individuals exposed to adverse thermal conditions.

Noise Effects on Human Performance: A Meta-Analytic Synthesis

Noise is a pervasive and influential source of stress. Whether through the acute effects of impulse noise or the chronic influence of prolonged exposure, the challenge of noise confronts many who must accomplish vital performance duties in its presence. Although noise has diffuse effects, which are shared in common with many other chronic forms of stress, it also exerts its own specific influences on various forms of cognitive and motor response. We present a quantitative evaluation of these influences so that their harmful effects can be mitigated, their beneficial effects exploited, and any residual effects incorporated and synthesized into selection, training, and design strategies to facilitate human performance capacities. Predictions of single and joint moderator effects were made on the basis of major theories of noise and performance, specifically those explanations based on arousal, masking, or cognitive-resource mechanisms. These predictions were tested through moderator analyses of effects as a function of task type, performance measure, noise type and schedule, and the intensity and duration of exposure. Observed outcome effects (797 effect sizes derived from 242 studies) varied as a function of each of these moderators. Collective findings identified continuous versus intermittent noise, noise type, and type of task as the major distinguishing characteristics that moderated response. Mixed evidence was obtained for the traditional arousal and masking explanations for noise effects. The overall pattern of findings was most consistent with the maximal adaptability theory, a mental-resource-based explanation of stress and performance variation.

Effects of Sensory Modality and Task Duration on Performance, Workload, and Stress in Sustained Attention

The workload and stress associated with a 40-min vigilance task were examined under conditions wherein observers monitored an auditory or a visual display for changes in signal duration. Global workload scores fell in the midrange of the NASA Task Load Index, with scores on the Frustration subscale increasing linearly over time. These effects were unrelated to the sensory modality of signals. However, sensory modality was a significant moderator variable for stress. Observers became more stressed over time as indexed by responses to the Dundee Stress State Questionnaire, with evidence of recovery in the auditory but not the visual condition toward the end of the watch. This result and the finding that signal detection accuracy - although equated for difficulty under alerted conditions - favored the auditory mode, indicate that display modality and time on task should be considered carefully in the design of operations requiring sustained attention in order to enhance performance and reduce stress. Actual or potential applications of this research include domains in which monitoring is a crucial part, such as baggage screening, security operations, medical monitoring, and power plant operations.

Training for vigilance: the effect of knowledge of results format and dispositional optimism and pessimism on performance and stress.

This study investigated the impact of knowledge of results (KR) format on the performance and stress associated with a vigilance task. Also examined was the effect of the interaction of KR-format (Hit-KR, False Alarm-KR, Miss-KR, and a composite of all three formats) with dispositional optimism and pessimism on performance outcome and reported stress state. Hypotheses based upon a theory of feedback intervention were tested. KR regarding correct detections and the composite-KR (KR regarding correct detections, false alarms, and missed signals) enhanced perceptual sensitivity. However, False Alarm-KR and Miss-KR did not. Contrary to expectations based on the theory, performance was unrelated to the traits across all KR conditions. However, the effects of KR-format on self-reports of stress depended on the individuals level of pessimism and optimism. In addition, KR format and personality affected the multiple dimensions of stress state in different ways.

Individual differences in human–technology interaction: incorporating variation in human characteristics into human factors and ergonomics research and design

This paper argues for incorporation of an individual differences approach into human factors/ergonomics research and practice. Description of the systematic variation in the human portion (e.g. cognitive and personality traits; motivational and emotional states) of human–technology systems can complement the existing design methods (e.g. task analysis) to yield better models of system performance and improve system design and operation. Individual differences research should not and need not be atheoretical and opportunistic and applications should not and need not be restricted to selection. Instead, consideration of individual differences will lead to a more inclusive human factors/ergonomics in which the properties of the human are described in a level of detail commensurate with the properties of the displays and controls. Three theories are described and their implications for human factors/ergonomics are discussed. Key issues for future research and practice are identified, including a set of guidelines for implementing an individual differences approach.

A Meta-Analysis of Factors Influencing the Development of Trust in Automation: Implications for Understanding Autonomy in Future Systems.

Objective: We used meta-analysis to assess research concerning human trust in automation to understand the foundation upon which future autonomous systems can be built. Background: Trust is increasingly important in the growing need for synergistic human–machine teaming. Thus, we expand on our previous meta-analytic foundation in the field of human–robot interaction to include all of automation interaction. Method: We used meta-analysis to assess trust in automation. Thirty studies provided 164 pairwise effect sizes, and 16 studies provided 63 correlational effect sizes. Results: The overall effect size of all factors on trust development was ḡ = +0.48, and the correlational effect was r ¯  = +0.34, each of which represented medium effects. Moderator effects were observed for the human-related (ḡ  = +0.49; r ¯ = +0.16) and automation-related (ḡ = +0.53; r ¯ = +0.41) factors. Moderator effects specific to environmental factors proved insufficient in number to calculate at this time. Conclusion: Findings provide a quantitative representation of factors influencing the development of trust in automation as well as identify additional areas of needed empirical research. Application: This work has important implications to the enhancement of current and future human–automation interaction, especially in high-risk or extreme performance environments.

Individual differences in response to automation: the five factor model of personality.

This study examined the relationship of operator personality (Five Factor Model) and characteristics of the task and of adaptive automation (reliability and adaptiveness-whether the automation was well-matched to changes in task demand) to operator performance, workload, stress, and coping. This represents the first investigation of how the Five Factors relate to human response to automation. One-hundred-sixty-one college students experienced either 75% or 95% reliable automation provided with task loads of either two or four displays to be monitored. The task required threat detection in a simulated uninhabited ground vehicle (UGV) task. Task demand exerted the strongest influence on outcome variables. Automation characteristics did not directly impact workload or stress, but effects did emerge in the context of trait-task interactions that varied as a function of the dimension of workload and stress. The pattern of relationships of traits to dependent variables was generally moderated by at least one task factor. Neuroticism was related to poorer performance in some conditions, and all five traits were associated with at least one measure of workload and stress. Neuroticism generally predicted increased workload and stress and the other traits predicted decreased levels of these states. However, in the case of the relation of Extraversion and Agreeableness to Worry, Frustration, and avoidant coping, the direction of effects varied across task conditions. The results support incorporation of individual differences into automation design by identifying the relevant person characteristics and using the information to determine what functions to automate and the form and level of automation.

A quantitative meta-analytic examination of whole-body vibration effects on human performance.

Whole-body vibration exerts a substantive influence in many work environments. The primary objective for this work was to quantify such effects by identifying those moderating variables that influence the degree to which performance is affected. To achieve this, a comprehensive meta-analysis was conducted, which synthesized the existing research evidence. A total of 224 papers and reports were identified and, from these 115 effect sizes were derived from 13 experiments that survived the screening procedure. Results indicate that vibration acts to degrade the majority of goal-related activities, especially those with high demands on visual perception and fine motor control. Gaps in the current research literature are identified and suggestions offered with regard to a more theoretically-driven approach to testing vibration effects on human performance.

The future of neuroergonomics

This paper addresses the theoretical, the philosophical, and the ethical considerations associated with the advent and future of neuroergonomics. These issues will demand increasing attention as knowledge of the linkage of brain function to technology-based action improves from its current coarse-grained level to a more fine-grained understanding. These developments promise to open extraordinary opportunities for improved human-machine and human-human interaction, and represent the next major step in human-machine evolution. The social and psychological implications of these changes, however, must be considered if abuse of this conception is to be circumvented.