The Handbook of Operator Fatigue provides a comprehensive account of this subject to serve as the definitive reference work for researchers, students and practitioners alike. The volume features 30 ...chapters written by experts to address each important facet of fatigue, including: the scale of the fatigue problem, the nature of fatigue, how to assess fatigue, the impact of fatigue on health, fatigue in the workplace, the neurological basis of fatigue, sleep disorders, and the design of countermeasures to fatigue.
States of fatigue are implicated in driver impairment and motor vehicle accidents. This article reports two studies investigating two possible mechanisms for performance impairment: (1) loss of ...attentional resources; and (2) active regulation of matching effort to task demands. The first hypothesis predicts that fatigue effects will be accentuated by high task demands, but the second hypothesis predicts that fatigue effects will be strongest in "underload" conditions. In two studies, drivers performed a stimulated driving task, in which task demands were manipulated by varying road curvature. In a "fatigue induction" condition, the early part of the drive was occupied by performance of a demanding secondary task concurrently with driving, after which the concurrent task ceased. Post-induction driving performance was compared with a control condition in which drivers were not exposed to the induction. In both studies, the fatigue induction elicited various subjective fatigue and stress symptoms, and also raised reported workload. Fatigue effects on vehicle control and signal detection were assessed during and after the fatigue induction. The fatigue induction increased heading error, reduced steering activity, and, in the second study, reduced perceptual sensitivity on a secondary detection task. These effects were confined to driving on straight rather than on curved road sections, consistent with the effort regulation hypothesis. The second study showed that fatigue effects were moderated by a motivational manipulation. Results are interpreted within a control model, such that task-induced fatigue may reduce awareness of performance impairment, rather than reluctance or inability to mobilize compensatory effort following detection of impairment.
This paper reports the findings of two field studies of Australian drivers in which individual differences in stress and fatigue were investigated. In the first study, 58 professional drivers ...completed measures of mood, fatigue and other subjective stress state measures, before and after performing a prolonged driving trip. The results indicated that the scales were sensitive to increased fatigue following the driving trip, and correlated appropriately with Fatigue Proneness, a driver stress trait. In the second study, 104 non-professional drivers completed identical subjective stress state measures as the professional drivers, before and after performing a driving trip. Drivers completed a measure of driving-related stress traits, the Driver Stress Inventory (DSI), and a measure of coping, the Driving Coping Questionnaire (DCQ). Both measures were predictive of state response to driving, and the association between Fatigue Proneness and post-drive fatigue found in the first study was replicated. Findings from these studies suggest that fatigue and stress reactions to driving are psychometrically distinct, but may have some common antecedents, such as use of emotion-focused coping. The studies confirm the importance of fatigue and stress as potential safety problems, but also highlight the role of individual differences in response to the demands of driving.
The suggestion that utility is logically necessary for behavioural adjustments to be made in response to changes in intrinsic risk is fundamental to risk homeostasis theory (RHT). However, the ...methodology used to investigate RHT — analysis of road traffic accidents — is ill-suited to the investigation of this assertion. The role of utility and intrinsic risk as possible determinants of behavioural compensation were therefore examined experimentally across 14 specific behaviours using the Aston Driving Simulator. RHT predicts that these two factors act in a multiplicative way to form a statistical interaction. It also predicts that the behavioural pathways through which the effect manifests itself should be reconcilable with the concept of utility. Both predictions received little support in this experiment, suggesting that utility and intrinsic risk operate as independent factors: both factors produced significant main effects across a number of behaviours. This finding, if it can be generalised, implies that, contrary to mathematically-based models of danger compensation and the traditional model of risk homeostasis, utility is not logically necessary for behavioural compensation in response to a change in intrinsic risk.
Air traffic control operations provide a potential example of risk homeostasis theory (RHT) in a non-transportational domain. This paper addresses the issue of whether reductions in intrinsic risk ...can be negated by behavioural adjustments of operators. Following variations in mental workload, previous studies have suggested that air traffic controllers appear to adapt to changing demands through more active or more effective strategic control of performance. This effortful compensatory control of performance has the consequence of eliminating what would otherwise be concomitant variations in accident loss. However, most of the empirical support for this proposition is taken from observational studies in which the relative occurrence of different levels of workload is not controlled. Using a simulated air traffic control task, a study is reported here in which conditions of low, moderate and high levels of mental workload are presented in equal duration to participants. The findings indicate that number of errors differed significantly across these conditions of mental workload which is contrary to what RHT would predict. Evidence is found for a general adaptation (or strategy switching) in response to different levels of workload. This supports earlier work in indicating that behavioural adjustments may not be of sufficient magnitude to restore previously existing levels of safety. However, on a notional measure of extrinsic compensation, participants did respond differently according to workload, thus lending limited support to RHT's prediction that utility and intrinsic risk should act in a multiplicative way to form a statistical interaction.
This chapter seeks to define the concept of fatigue. It looks to approach the question of the definition and conceptualization of fatigue largely from an evolutionary perspective. The chapter ...identifies a candidate metabolic source of energy as the rate-limiting factor in fatigue and have suggested that this is strongly linked to the psychological construct of attentional resources. It shows that fatigue can be considered a chronic form of stress. The chapter discusses that the protestation of a single aspect of the overall biochemical balance of the brain is most probably a very simplistic representation of the situation. Cognitive fatigue, then, is a chronic state of attentional resource depletion very much related to the biochemical substrate energy that supports ongoing activity. Humans experience cognitive fatigue because they have developed very costly brains so that they can substitute cognitive search strategies for the eventually more costly physical search strategies.
Although the history of recognition of child abuse in Europe and North America extends over 40 years, recognition and data are lacking in other parts of the world. Cultural differences in ...child-rearing complicate cross-cultural studies of abuse.
To ascertain rates of harsh and less-harsh parenting behavior in population-based samples.
We used parallel surveys of parental discipline of children in samples of mothers in Brazil, Chile, Egypt, India, Philippines, and the United States. Data were collected between 1998 and 2003. The instrument used was a modification of the Parent-Child Conflict Tactics Scale, along with a study-developed survey of demographic characteristics and other parent and child variables. Women (N=14 239) from 19 communities in 6 countries were surveyed. We interviewed mothers aged 15 to 49 years (18-49 years in the United States) who had a child younger than 18 years in her home. Sample selection involved either random sampling or systematic sampling within randomly selected blocks or neighborhoods.
Nearly all parents used nonviolent discipline and verbal or psychological punishment. Physical punishment was used in at least 55% of the families. Spanking rates (with open hand on buttocks) ranged from a low of 15% in an educated community in India to a high of 76% in a Philippine community. Similarly, there was a wide range in the rates of children who were hit with objects (9%-74% median: 39%) or beaten by their parents (0.1%-28.5%). Extremely harsh methods of physical punishment, such as burning or smothering, were rare in all countries. It is concerning that >or=20% of parents in 9 communities admitted shaking children younger than 2 years.
Physical and verbal punishments of children are common in high-, middle-, and low-income communities around the world. The forms and rates of punishment vary among countries and among communities within countries. A median of 16% of children experienced harsh or potentially abusive physical discipline in the previous year.
This thesis attempted to provide a detailed theoretical understanding of the effects of task-induced fatigue on simulated driving performance. Previous research has shown that duration of driving has ...only a weak effect on driving performance. A series of studies were conducted to examine how fatigue effects interact with task demands, and to explore the psychological changes associated with fatigue. The research also explored links between fatigue and stress in terms of their affective reactions and the coping mechanisms which are central to them. The first phase of the research consisted of a series of simulated studies of fatigue. The first study developed an experimental paradigm to examine both task-specific and aftereffects of fatigue on driving performance. The findings showed that fatigue effects interacted with task demands such that drivers' lateral control of the vehicle and trajectory were impaired during low demand rather than in high demand driving episodes. The study also showed that the fatigue state is a multidimensional state which is principally characterised by a reduction in motivation. The second and third studies attempted to explore the role of motivational mechanisms in fatigue-related impairments. This phase of the research showed that impairments in low demand driving conditions may be reduced by enhancing the driver's motivational state. The fourth study explored the development of subjective fatigue in two types of task-induced fatigue. The study showed that there is a dissociation between subjective and objective fatigue. The second phase of the research examined the links between stress and fatigue in simulated and real-life driving environments. The studies showed that stress and fatigue are similar states but there are particular features which make them distinct states. The results from simulated and real-life driving environments showed a high degree of consistency.
This thesis attempted to provide a detailed theoretical understanding of the effects of task-induced fatigue on simulated driving performance. Previous research has shown that duration of driving has ...only a weak effect on driving performance. A series of studies were conducted to examine how fatigue effects interact with task demands, and to explore the psychological changes associated with fatigue. The research also explored links between fatigue and stress in terms of their affective reactions and the coping mechanisms which are central to them. The first phase of the research consisted of a series of simulated studies of fatigue. The first study developed an experimental paradigm to examine both task-specific and aftereffects of fatigue on driving performance. The findings showed that fatigue effects interacted with task demands such that drivers' lateral control of the vehicle and trajectory were impaired during low demand rather than in high demand driving episodes. The study also showed that the fatigue state is a multidimensional state which is principally characterised by a reduction in motivation. The second and third studies attempted to explore the role of motivational mechanisms in fatigue-related impairments. This phase of the research showed that impairments in low demand driving conditions may be reduced by enhancing the driver's motivational state. The fourth study explored the development of subjective fatigue in two types of task-induced fatigue. The study showed that there is a dissociation between subjective and objective fatigue. The second phase of the research examined the links between stress and fatigue in simulated and real-life driving environments. The studies showed that stress and fatigue are similar states but there are particular features which make them distinct states. The results from simulated and real-life driving environments showed a high degree of consistency.
Traditional right ventricular apical pacing can, over time, result in deterioration of left ventricular function. In this comparative-effectiveness trial, biventricular pacing prevented the reduction ...in left ventricular ejection fraction that is seen with right ventricular pacing. The findings have implications for the treatment of patients with bradycardia who require permanent pacing.
This phase 2 study evaluated the role of B-lymphocyte depletion with rituximab in type 1 diabetes mellitus. Rituximab partially preserved beta-cell function over a 1-year period, suggesting that B lymphocytes contribute to the pathogenesis of type 1 diabetes mellitus.
The autoimmune destruction of beta cells in patients with type 1 diabetes mellitus begins before the onset of hyperglycemia, but measurement of C-peptide responses at the time of diagnosis indicates that patients retain some beta-cell function at this stage. Furthermore, the persistence of residual beta-cell function is associated with reductions of severe hypoglycemic episodes and complications.
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Thus, an intervention that maintains endogenous insulin production might improve the management of type 1 diabetes and reduce long-term complications.
Although the presence of autoantibodies is a diagnostic criterion, the immunopathogenesis of beta-cell destruction in type 1 diabetes is typically associated with T-lymphocyte autoimmunity. . . .
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