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Several lines of research on converge for the conclusion that high and low hostile men differ with respect to autonomic regulation of stress. The functional cerebral systems approach has provided a theoretical framework to account for this finding across the individual sensory, motor, and premotor modalities. The current experiment extends and elaborates upon a functional cerebral systems based model that posits a role for the right frontal region in regulation of sympathetic tone after stress. The experiment builds upon prior work illustrating the utility of this model to stress by positing mild dizziness as a potential frontal lobe stressor demonstrating hostility group differences in sympathetic arousal. Dizziness was induced by brief clockwise angular rotation about the vertical neuroaxis. Consistent with vestibular research indicating clockwise rotation impacts the right hemisphere (relative to counterclockwise rotation), it was expected that hostile individuals would exhibit higher skin conductance levels after rotation compared with low hostile individuals. The experiment also included a dichotic listening task both before and after rotation to examine the effects of rotary stress on dichotic phoneme identification. The experiment was conducted in three blocks: A dichotic listening task comprised the first block, followed by application of rotary stress as the second block, and a follow-up dichotic listening task post- rotary stress. It was predicted that rotation would induce an auditory perceptual shift towards the left ear. Results confirmed expected group differences in sympathetic response to rotary stress. High hostiles had greater overall skin conductance immediately following rotation. High hostiles failed to habituate skin conductance levels to mild rotation 7 minutes post-rotary stress. Lateralized effects of skin conductance remain unconfirmed at this time. No group differences were found for either block of the dichotic listening task. Overall, results are interpreted to support a model of frontal region capacity limitation for regulation of stress, including vestibular dysfunction. / Master of Science

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Thesis (M.S. in psychology)--Washington State University, May 2007. / Includes bibliographical references (p. 19-21).

Understanding how human and animal visual systems work is an important and still largely unsolved problem. The neural mechanisms for low-level visual processing have been studied in detail, focusing on early visual areas. Much less is known about the neural basis of high-level perception, particularly in humans. An important issue is whether and how lessons learned from low-level studies, such as how neurons in the primary visual cortex respond to oriented edges, can be applied to understanding highlevel perception, such as human processing of faces. Visual aftereffects are a useful tool for investigating how stimuli are represented, because they reveal aspects of the underlying neural organisation. This thesis focuses on identifying neural mechanisms involved in high-level visual processing, by studying the relationship between low- and high-level visual aftereffects. Previous psychophysical studies have shown that humans exhibit reliable orientation (tilt) aftereffects, wherein prolonged exposure to an oriented visual pattern systematically biases perception of other orientations. Humans also show face identity aftereffects, wherein prolonged exposure to one face systematically biases perception of other faces. Despite these apparent similarities, previous studies have argued that the two effects reflect different mechanisms, in part because tilt aftereffects show a characteristic S-shaped curve, with the effect magnitude increasing and then decreasing with orientation difference, while face aftereffects appeared to increase monotonically (in various units of face morphing strengths) with difference from a norm (average) face. Using computational models of orientation and face processing in the visual cortex, I show that the same computational mechanisms derived from early cortical processing, applied to either orientation-selective or face-selective neurons, are sufficient to replicate both types of effects. However, the models predict that face aftereffects would also be S-shaped, if tested on a sufficiently wide range of face stimuli. Based on the modelling work, I designed psychophysical experiments to test this theory. An identical experimental paradigm was used to test both face gender and tilt aftereffects, with strikingly similar S-shape curves obtained for both conditions. Combined with the modelling results, this result provides evidence that low- and high level visual adaptation reflect similar neural mechanisms. Other psychophysical experiments have recently shown interactions between low and high-level aftereffects, whereby orientation and line curvature processing (in early visual area) can influence judgements of facial emotion (by high-level face-selective neurons). An extended multi-level version of the face processing model replicates this interaction across levels, but again predicts that the cross-level effects will show similar S-shaped aftereffect curves. Future psychophysical experiments can test these predictions. Together, these results help us to understand how stimuli are represented and processed at each level of the visual cortex. They suggest that similar adaptation mechanisms may underlie both high-level and low-level visual processing, which would allow us to apply much of what we know from low-level studies to help understand high-level processing.

[Truncated abstract] Recent studies have provided evidence that face-coding mechanisms reference a norm or average face (Leopold, O`Toole, Vetter & Blanz, 2001; Rhodes & Jeffery, 2006). The central aim of this thesis was to establish whether distinct norms, and dissociable neural mechanisms code faces of different race and sex categories. Chapter 1 provides a brief introduction to norm based coding of faces, and reviews evidence for the existence of distinct norms for different races and sexes. Chapter 1 then introduces adaptation as a tool for investigating these ideas. Chapter 2 presents two adaptation studies that examined how faces of different races are coded. The aim of these studies was to determine whether dissociable neural mechanisms (or distinct face norms) code faces of different races. Chinese and Caucasian participants rated the normality of Caucasian and Chinese test faces, before and after adaptation to distorted faces of one race (e.g., 'contracted' Chinese faces; Experiment 1) or distorted faces of both races (e.g., 'contracted' Chinese faces and 'expanded' Caucasian faces; Experiment 2). Following adaptation to faces of one race, there were changes in perceived normality for faces of both races (i.e., perceptual aftereffects), indicating that common neural mechanisms code Chinese and Caucasian faces. However, aftereffects were significantly smaller in faces of the unadapted race suggesting some sensitivity to the race of faces. This sensitivity was also evident in Experiment 2. ... Some dissociability was also found in the coding of faces of different iv sexes. In Experiments 2 and 3, participants adapted to oppositely distorted faces of both sexes. Weak sex-selective aftereffects were found. Taken together, the findings suggest that male and female faces are coded by dissociable but not completely distinct neural populations. Chapter 4 examined whether the aftereffects reported for faces of different races or sexes reflected the adaptation of high-level neural mechanisms tuned to the social category information in faces, or earlier coding mechanisms tuned to simple physical differences between face groups. Chinese and Caucasian participants adapted to oppositely distorted face sets that were the same distance apart on a morph continua. The face sets were either from different race categories (e.g., contracted Chinese faces and expanded Caucasian faces), or from the same race category, (e.g., contracted Chinese faces and expanded caricatured Chinese faces). Larger opposite aftereffects were found when face sets were from different race categories, than when they were from the same race category suggesting that oppositely adapted neural mechanisms are tuned to social category differences rather than simple physical differences in faces. Together, these studies shed new light on how we code faces from different face categories. Specifically, the findings indicate that faces of different races and sexes are coded by both common and race- or sex-selective neural mechanisms. In addition, the findings are consistent with the possibility that race- and sex-selective norms and dimensions are used to code faces in face space. The implications of these findings and possible avenues for future research are discussed.

Individuals with autism spectrum disorder (ASD) have difficulties in many areas of social cognition including face perception. Decades of research examining face processing abilities in ASD populations have yielded equivocal results. The current thesis includes a series of experiments intended to clarify the nature of the face processing deficits seen in ASD. In Study 1 I examined norm-based coding of facial identity in adults with ASD. I measured identity aftereffects in adults with and without ASD and found no significant group differences. In Study 2 I examined simple (Experiment 1) and opposing (Experiment 2) figural aftereffects for male and female faces and found no significant group differences as adults with ASD. In Study 3 I examined perceptual strategies employed by adults with ASD when processing emotional facial expressions and found that adults with ASD employ a rule-based strategy. Finally, in Study 4 I examined what drives face processing deficits in adults with ASD; deficits in processing emotional information in faces or a deficit in processing socially complex information in faces. I found that adults with ASD had a deficit in discriminating basic and complex emotional facial expressions, suggesting that emotion-perception demands are associated with poor face processing in ASD. The results of the studies demonstrate that adult with ASD show typical perceptual mechanisms underlying face perception, use an atypical perceptual strategies when processing facial expressions, and have a specific deficit in processing emotional expressions. / Thesis / Doctor of Philosophy (PhD)

In a series of two experiments, the first involving 121 participants and the second 114, I investigated whether level of racial prejudice is related to performance on a cognitive task and helping behavior in participants who had just interacted with the target of their prejudice. The moderating effect of control was tested and, unlike previous research, the responses of African-American participants were studied too. It was proposed that when people interact with the target of their prejudice, they will experience stress and the aftereffects of stress will lead to a decrement in Stroop task performance and a lower likelihood of helping someone in need. Control was believed to moderate this effect such that those given control would suffer less of a performance decrement and would help more often. Data were analyzed using ANCOVA and logistic regression. Racial prejudice was found to affect European-American but not African-American Stroop performance following the interracial interaction. Control moderated this effect and also influenced whether someone helped a person in need.