While it is well established that expert performers can pick up and utilise postural cues to anticipate more effectively than less-skilled counterparts, the role of contextual information in expert anticipation has received relatively little research attention. The aims of this thesis were to highlight the importance of contextual information in anticipation, identify specific sources of contextual information that impact anticipation, and examine how this information is used. In five studies, skilled and less-skilled tennis players were presented with videos or animations of the same open play rallies. The animations omitted postural information, constraining participants to anticipate based on contextual information alone. First, participants anticipated more accurately than chance in both display conditions. Skilled participants were more accurate than less-skilled participants, with the difference being greater in the video condition. Second, gaze data and retrospective verbal reports were collected when viewing the animations. Skilled participants displayed different gaze behaviour and more thoroughly evaluated the presented information than less-skilled participants. Third, animations were manipulated to depict or omit potential sources of contextual information. The preceding shot sequence was shown to be a useful source of contextual information, particularly for skilled participants. Additionally, player positioning could be used to anticipate highly accurately in absence of any other information. Finally, the option generation strategies underpinning expert anticipation were examined. Participants generated fewer options when postural cues were available compared with when constrained to the use of contextual information alone. Moreover, skilled participants generated more task-relevant and fewer task-irrelevant options than less-skilled participants. Collectively, these findings increase understanding of the role of contextual information in expert anticipation and further highlight the complex nature of perceptual-cognitive expertise.

This thesis offers a fresh interpretation and defense of epistemological disjunctivism about perceptual knowledge. I adopt a multilevel approach according to which perceptual knowledge on one level can enjoy factive rational support provided by perceptual knowledge of the same proposition on a different level. Here I invoke a distinction Ernest Sosa draws between 'judgmental' and 'merely functional' belief to articulate what I call the bifurcated conception of perceptual knowledge. The view that results is a form of epistemological disjunctivism about perceptual knowledge specifically at the higher judgmental level, layered over a straightforward externalism about perceptual knowledge at the lower merely functional level. The first chapter orients the reader to epistemological disjunctivism- with particular emphasis on the 'reflective epistemological disjunctivism' defended by Duncan Pritchard with inspiration from John McDowell. Here I review the arguments for thinking such a proposal true, as well as highlight some problems and three emerging challenges for the view: what I call the internalist challenge, the new access challenge(s), and the 'new evil genius' challenge. These challenges largely inspire the chapters to follow. In the second chapter I present the positive proposal: a fresh interpretation of epistemological disjunctivism in terms of perceptual knowledge at the specifically judgmental level. I argue that this is a modification that epistemological disjunctivists should adopt since it inoculates their view against the internalist challenge: the challenge of explaining why perception should provide one with knowledge by providing one with motivating reasons for belief. In the third chapter I motivate the view further in connection with the more familiar 'basis problem' for epistemological disjunctivism. I argue that this approach supports a unique strategy for solving that problem: one that is consistent both with what is known as 'the entailment' thesis and the thought that we can reduce perceptual knowledge to a kind of rationally supported belief. In the fourth chapter I move to playing defense. I defend the proposal against the so-called 'new evil genius' challenge. This is the challenge to explain why subjects in pairs of 'good' and 'bad' cases can seem equally justified for sustaining their perceptual beliefs. I argue that what we are being sensitive to here, rather, is the fact that both subjects can be equally epistemically responsible and/or reasonable for believing what they do. Before concluding this chapter I also offer an error theory. In the fifth chapter I defend the proposal against the new access challenges raised in chapter one. These alleged challenges for epistemological disjunctivism arise specifically for versions of reflective epistemological disjunctivism that hold that one's rational support for perceptual beliefs is not only factive but reflectively accessible as well. Rather than address the challenges head on, I try to dislodge the thought they depend upon-viz., that one's factive rational support for perceptual beliefs is reflectively accessible to the subject. Here I argue that the reflective accessibility of one's factive rational support is actually a wheel turning idly in the debate with the underdetermination-based radical sceptic-so that we can simply drop it without consequence. The result is an epistemological disjunctivism that is immune to access problems. I then offer a final summary and conclude. At the end of this thesis I have attached an appendix, which is an excursion into religious epistemology and an exploration of a form of religious epistemological disjunctivism. Here I apply the epistemological disjunctivist insight to the case of religious perception in order to defend the idea that one can offer independent rational support for theistic belief by appealing to religious beliefs that are justified on the basis of religious experiences. This appendix chapter is in keeping with the general spirit of the thesis insofar as it seeks to developed epistemological disjunctivism in new and fruitful directions.

The work in this thesis explore the DWT based video coding by the introduction of a novel DWT (Discrete Wavelet Transform) / MC (Motion Compensation) / DPCM (Differential Pulse Code Modulation) video coding framework, which adopts the EBCOT as the coding engine for both the intra- and the inter-frame coder. The adaptive switching mechanism between the frame/field coding modes is investigated for this coding framework. The Low-Band-Shift (LBS) is employed for the MC in the DWT domain. The LBS based MC is proven to provide consistent improvement on the Peak Signal-to-Noise Ratio (PSNR) of the coded video over the simple Wavelet Tree (WT) based MC. The Adaptive Arithmetic Coding (AAC) is adopted to code the motion information. The context set of the Adaptive Binary Arithmetic Coding (ABAC) for the inter-frame data is redesigned based on the statistical analysis. To further improve the perceived picture quality, a Perceptual Distortion Measure (PDM) based on human vi sion model is used for the EBCOT of the intra-frame coder. A visibility assessment of the quantization error of various subbands in the DWT domain is performed through subjective tests. In summary, all these findings have solved the issues originated from the proposed perceptual video coding framework. They include: a working DWT/MC/DPCM video coding framework with superior coding efficiency on sequences with translational or head-shoulder motion; an adaptive switching mechanism between frame and field coding mode; an effective LBS based MC scheme in the DWT domain; a methodology of the context design for entropy coding of the inter-frame data; a PDM which replaces the MSE inside the EBCOT coding engine for the intra-frame coder, which provides improvement on the perceived quality of intra-frames; a visibility assessment to the quantization errors in the DWT domain.

Examination of how the brain mediates emotional experience is now an area of significant and intense research interest. This is an important endeavour considering that emotion is a key component in vulnerability factors governing risk for mood and anxiety disorders. Recent neuropsychological and neuroimaging studies are also beginning to explore the effects of antidepressants on the processing of emotional stimuli in healthy participants to help understand the role of neurochemicals in affective behaviour more broadly. Unfortunately the literature is fraught with contradictions and complications resulting from the technique used, task instructions, selection of stimuli and gender differences. The aim of the current thesis therefore, was to investigate emotional processing in healthy participants and to examine the impact of serotonergic augmentation on this processing through the presentation of visual emotional stimuli and examination of self report, peripheral- and neurophysiological measures of emotional responsiveness. Seventy five images low in arousal content, selected from the International Affective Picture System (IAPS) and categorised as pleasant, neutral and unpleasant, were presented to participants in four experimental studies. Findings support previous literature suggesting that there is substantial overlap in frontal neural circuitry when the brain processes emotional images of different valence. Gender differences in the processing of visual emotional stimuli were also observed however suggesting the need for future studies to take such factors into account. In particular, females unlike males displayed right-sided, frontal, neurophysiological activations in response to unpleasant relative to neutral images. Emotional valence was also found to modulate heart rate (HR) thereby confirming the reliability and validity of the task-viewing paradigm. Augmentation of serotonin was found to suppress any differences in HR across the three differently valenced categories of images, while neurophysiological responses were potentiated during pleasant valence but suppressed during unpleasant valence. In summary, the studies included in this thesis provide evidence for neurophysiological modulation by emotional content and gender. In addition, the studies employ a more systems-based approach to the study of antidepressant action, through examination of the neurophysiological responses to visual emotional stimuli. This approach may lead to greater understanding of the functional consequences of neurochemical modulation on cortical networks involved in emotional processing.

This exploratory study examined outcomes of single telephone counselling calls, with a self-selected sample of 38 clients from a family counselling agency. The sample was interviewed by telephone at two days and six weeks after the call to assess crisis counselling outcomes in affect, identification of the problem and action taken, and client equilibrium. Repeated measures of the 'perceptual concordance' of counsellor and client were taken over a period of six weeks, assessing levels of concordance between client and counsellor about perceptions of counselling, and client equilibrium. The sufficiency of a single counselling session was also assessed. 'Perceptual concordance' was suggested by reduced client stress, high levels of agreement between client and counsellor in the identification of the problem and agreed action, and satisfaction with the counselling. Positive indicators of restored client equilibrium included a maintenance of lower stress levels, changes in behaviour, improvement in perceptions of the seriousness of the problem, satisfaction with life and with the counselling. Further research of equilibrium as a concept, and an indicator of crisis resolution is warranted. The sufficiency of a single session of counselling was supported by 56% of clients. The variety of services used by clients as an outcome of the counselling suggests that it could be beneficial for telephone counselling agencies to offer a follow-up call. Verifying the agreed action and assessing equilibrium could be useful indicators of effective telephone counselling.

Discrimination between similar stimuli is enhanced more by intermixed pre-exposure than by blocked pre-exposure to those stimuli. The salience modulation account of this intermixed-blocked effect proposes that the unique elements of intermixed stimuli are more salient than those of blocked stimuli. The inhibition account proposes that inhibitory links between the unique elements of intermixed stimuli enhance discrimination. The current thesis evaluated the two accounts in their ability to explain this effect in humans. In Experiments 1 and 2, categorisation and same-different judgements were more accurate for intermixed than for blocked stimuli. This indicates that intermixed pre-exposure decreases generalisation and increases discriminability more than does blocked pre-exposure. In Experiments 3 ?? 5, same-different judgements were more accurate when at least one of the two stimuli was intermixed. This enhanced discrimination was not confined to two stimuli that had been directly intermixed. These results are better explained by salience modulation than by inhibition. Experiments 6 ?? 8 employed dot probe tasks, in which a grid stimulus was followed immediately by a probe. Neither intermixed nor blocked stimuli showed facilitated reaction times when the probe appeared in the location of the unique element. In Experiments 9 ?? 11 participants learned to categorise the intermixed unique elements more successfully than the blocked unique elements, but only when the unique elements were presented on a novel background during categorisation. Experiments 6 ?? 11 provide weak evidence that the intermixed unique elements are more salient than their blocked counterparts. In Experiment 12, participants were presented with the shape and location of a given unique element, and were required to select the correct colour. Performance was more accurate for intermixed than for blocked unique elements. In Experiment 13, participants learned to categorise intermixed, blocked and novel unique elements. Performance was better for intermixed than for blocked and novel unique elements, which did not differ. None of the proposed mechanisms for salience modulation anticipate these results. The intermixed-blocked effect in human perceptual learning is better explained by salience modulation than by inhibition. However, the salience modulation accounts that have been proposed received little support. An alternative account of salience modulation is considered.

Brightness judgments are a key part of the primate brain's visual analysis of the environment. There is general consensus that the perceived brightness of an image region is based not only on its actual luminance, but also on the photometric structure of its neighborhood. However, it is unclear precisely how a region's context influences its perceived brightness. Recent research has suggested that brightness estimation may be based on a sophisticated analysis of scene layout in terms of transparency, illumination and shadows. This work has called into question the role of low-level mechanisms, such as lateral inhibition, as explanations for brightness phenomena. Here we describe experiments with displays for which low-level and high-level analyses make qualitatively different predictions, and with which we can quantitatively assess the trade-offs between low-level and high-level factors. We find that brightness percepts in these displays are governed by low-level stimulus properties, even when these percepts are inconsistent with higher-level interpretations of scene layout. These results point to the important role of low-level mechanisms in determining brightness percepts.

Thesis (Ph.D.)--York University, 2004. Graduate Programme in Biology. / Typescript. Includes bibliographical references (leaves 292-305). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNQ99265

Previous work suggests that both concrete (e.g., hat, shoes) and abstract (e.g., god, devil) concepts with spatial associations engage attentional mechanisms, affecting subsequent target processing above or below fixation. Interestingly, both facilitatory and inhibitory effects have been reported to result from compatibility between target location and the meaning of the concept. To determine the conditions for obtaining these disparate effects, we varied the task (detection vs. discrimination), SOA, and concept type (abstract vs. concrete) across a series of experiments. Results suggest that the nature of the concepts underlies the different attentional effects. With abstract concepts, facilitation was observed across tasks and SOAs. With concrete concepts, inhibition was observed during the discrimination task and for short SOAs. Thus, the particular perceptual and metaphorical associations of a concept mediate their subsequent effects on visual target processing.

Previous work suggests that both concrete (e.g., hat, shoes) and abstract (e.g., god, devil) concepts with spatial associations engage attentional mechanisms, affecting subsequent target processing above or below fixation. Interestingly, both facilitatory and inhibitory effects have been reported to result from compatibility between target location and the meaning of the concept. To determine the conditions for obtaining these disparate effects, we varied the task (detection vs. discrimination), SOA, and concept type (abstract vs. concrete) across a series of experiments. Results suggest that the nature of the concepts underlies the different attentional effects. With abstract concepts, facilitation was observed across tasks and SOAs. With concrete concepts, inhibition was observed during the discrimination task and for short SOAs. Thus, the particular perceptual and metaphorical associations of a concept mediate their subsequent effects on visual target processing.