Acute stress has numerous potential consequences for individuals, from their behaviour to their performance on a task. Psychological models like the biopsychosocial model (BPSM) of challenge and threat, the theory of challenge and threat states in athletes (TCTSA) and the integrative framework of stress, attention, and visuomotor performance (IFSAVP) have attempted to explain the variability in individual responses to stress in motivated performance situations. The BPSM proposes that individuals engaged in a task make conscious and unconscious evaluations of the situational demands, such as the required effort, and their personal resources, such as their abilities. These demand-resource evaluations result in relatively different psychological outcomes namely, challenge and threat responses which represent two ends of a continuum. Both the BPSM and the TCTSA suggest that these psychological consequences have corresponding physiological responses allowing for objective measurements of challenge and threat responses. Performance differences have been observed between challenged and threatened individuals across a range of tasks, although motor tasks have been relatively under-examined within this context. Furthermore, as put forward in the IFSAVP, challenge responses are associated with better attentional control compared with threat responses though this has also been under-examined. As challenge responses are characterised by better physiological, performance and attentional outcomes, it is important to understand what determines challenge and threat responses. Therefore, the aim of this thesis was to examine key determinants of challenge and threat responses and to replicate and extend findings regarding performance and attentional outcomes. Four experimental studies were conducted to test proposed determinants and the aforementioned outcomes. Arousal reappraisal and self-efficacy were found to be determinants of challenge and threat responses across both subjective (self-report) and objective (cardiovascular reactivity) measures. Self-control was shown not to influence challenge and threat responses via either measure while situational motivation regulations predicted only subjective but not objective measures of challenge and threat. Importantly, situational motivation regulations also predicted task engagement, a prerequisite of challenge and threat responses. Across all four studies, there were no performance effects and of the three studies which examined attention, there were no attention effects. Descriptive data trends however, indicated a more complex and nuanced relationship between challenge and threat responses and performance and attention. The findings of this thesis develop the BPSM, the TCTSA and the IFSAVP. They also have several other theoretical and practical implications.

Autism Spectrum Disorder (ASD) is a pervasive developmental disorder characterized by two distinct features; the social, including impairments in communication and social functioning (empathizing), and the non-social, including preoccupation with restricted interests and repetitive behaviours (systemizing). This thesis investigated non-social cognition in the autism spectrum by undertaking six studies, three with neurotypical participants from the general population and three with an ASD group and matched neurotypical controls. These studies measured autonomic arousal to social and non-social stimuli and stimuli associated with the participant's own special interest or hobby, and change blindness tasks that utilized both social and non-social changes, along with measures of attention to detail and anxiety in an attempt to understand some of the cognitive and affective mechanisms that underlie non-social cognition in ASD and in the wider autism spectrum. A further study assessed 'drive to systemize' along with an objective behavioural assessment of logical thinking ability and a measure of preference for deliberative or intuitive thinking style, to try to further elucidate connections between drive to systemize and ability to systemize, and the modes of cognition that relate to systemizing. Findings included the relationship between autistic traits and stronger physiological responses to non-social stimuli in the neurotypical sample, and a significantly stronger response in the ASD group to non-social stimuli related to personal special interest than in controls. Participants with a larger number of autistic traits showed enhanced change blindness when changes were social in nature. Self-reported high systemizers report that they prefer slow, deliberative styles of thinking and provide more accurate responses to questions that should involve logical thinking-yet they are less able to provide sound logical reasoning for their correct answers than those who are low systemizers. Together, the results suggest that non-social cognition, or systemizing, in autism is motivated by bottom up perceptual and affective processes that share features with conventional social and emotional cognition, or empathizing.

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Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

Thesis (Ph. D.)--University of Pennsylvania, 1918. / "Reprinted from the Psychological clinic, vol. XII, no. 3, May 15, 1918." Bibliography: p. 24.

Thesis (Ph. D.)--University of Pennsylvania, 1918. / Bibliography: p. 54.

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