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.
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.
The immunopathogenesis of type 1 diabetes mellitus is associated with T-lymphocyte autoimmunity. However, there is growing evidence that B lymphocytes play a role in many T-lymphocyte-mediated ...diseases. It is possible to achieve selective depletion of B lymphocytes with rituximab, an anti-CD20 monoclonal antibody. This phase 2 study evaluated the role of B-lymphocyte depletion in patients with type 1 diabetes.
We conducted a randomized, double-blind study in which 87 patients between 8 and 40 years of age who had newly diagnosed type 1 diabetes were assigned to receive infusions of rituximab or placebo on days 1, 8, 15, and 22 of the study. The primary outcome, assessed 1 year after the first infusion, was the geometric mean area under the curve (AUC) for the serum C-peptide level during the first 2 hours of a mixed-meal tolerance test. Secondary outcomes included safety and changes in the glycated hemoglobin level and insulin dose.
At 1 year, the mean AUC for the level of C peptide was significantly higher in the rituximab group than in the placebo group. The rituximab group also had significantly lower levels of glycated hemoglobin and required less insulin. Between 3 months and 12 months, the rate of decline in C-peptide levels in the rituximab group was significantly less than that in the placebo group. CD19+ B lymphocytes were depleted in patients in the rituximab group, but levels increased to 69% of baseline values at 12 months. More patients in the rituximab group than in the placebo group had adverse events, mostly grade 1 or grade 2, after the first infusion. The reactions appeared to be minimal with subsequent infusions. There was no increase in infections or neutropenia with rituximab.
A four-dose course of rituximab partially preserved beta-cell function over a period of 1 year in patients with type 1 diabetes. The finding that B lymphocytes contribute to the pathogenesis of type 1 diabetes may open a new pathway for exploration in the treatment of patients with this condition. (ClinicalTrials.gov number, NCT00279305.)
Dimensional Models of Fatigue Matthews, Gerald; Desmond, Paula A.; Hitchcock, Edward M.
The Handbook of Operator Fatigue,
2012
Book Chapter
This chapter addresses dimensional models that may guide research on fatigue, including the choice of instruments for fatigue assessment. It presents the model as a framework for clarifying some of ...the different types of fatigue assessment that may be used in research. The chapter introduces a tentative general taxonomy of fatigue constructs that may be useful in guiding assessment efforts. It focuses on the assessment of fatigue vulnerability, the vicissitudes of objective fatigue assessments and a comprehensive state model for mental fatigue dimensions. The chapter also presents taxonomy that helps to differentiate some of the multiple expressions of fatigue states. In the realm of mental fatigue, use of self-report requires comprehensive dimensional models supporting state scales validated against objective measures. Theoretical understanding of state dimensions, whether based on cognitive stress theory or neuropsychology, is also essential.
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