Texte actualisé de: Th. doct.--Louvain, 1988.

Zugl.: Diss. Univ. Saarbrücken, 2008.

Thesis (MSocSci(Sociology))-University of Pretoria, 2008. / Includes bibliographical references.

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Social perception is dynamic and ambiguous. Whilst previous research favoured bottom-up views where observed actions are matched to higher level (or motor) representations, recent accounts suggest top-down processes where prior knowledge guides perception of others’ actions, in a predictive manner. This thesis investigated how person-specific models of others’ typical behaviour in different situations are reactivated when they are re-encountered and predict their actions, using strictly controlled computer-based action identification tasks, event-related potentials (ERPs), as well as recording participants’ actions via motion tracking (using the Microsoft Kinect Sensor). The findings provided evidence that knowledge about seen actor’s typical behaviour is used in action observation. It was found, first, that actions are identified faster when performed by an actor that typically performed these actions compared to another actor who only performed them rarely (Chapters Two and Three). These effects were specific to meaningful actions with objects, not withdrawals from them, and went along with action-related ERP responses (oERN, observer related error negativity). Moreover, they occurred despite current actor identity not being relevant to the task, and were largely independent of the participants’ ability to report the individual’s behaviour. Second, the findings suggested that these predictive person models are embodied such that they influenced the observers own motor systems, even when the relevant actors were not seen acting (Chapter Four). Finally, evidence for theses person-models were found when naturalistic responding was required when participants had to use their feet to ‘block’ an incoming ball (measured by the Microsoft Kinect Sensor), where they made earlier and more pronounced movements when the observed actor behaved according to their usual action patterns (Chapter Five). The findings are discussed with respect to recent predictive coding theories of social perception, and a new model is proposed that integrates the findings.

State-of-the-art temporal action detectors inefficiently search the entire video for specific actions. Despite the encouraging progress these methods achieve, it is crucial to design automated approaches that only explore parts of the video which are the most relevant to the actions being searched. To address this need, we propose the new problem of action spotting in videos, which we define as finding a specific action in a video while observing a small portion of that video. Inspired by the observation that humans are extremely efficient and accurate in spotting and finding action instances in a video, we propose Action Search, a novel Recurrent Neural Network approach that mimics the way humans spot actions. Moreover, to address the absence of data recording the behavior of human annotators, we put forward the Human Searches dataset, which compiles the search sequences employed by human annotators spotting actions in the AVA and THUMOS14 datasets. We consider temporal action localization as an application of the action spotting problem. Experiments on the THUMOS14 dataset reveal that our model is not only able to explore the video efficiently (observing on average 17.3% of the video) but it also accurately finds human activities with 30.8% mAP (0.5 tIoU), outperforming state-of-the-art methods

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In recent years, students have been excluded from school at consistently high rates, even as school crime rates have declined. Moreover, students of color are excluded at disproportionately high rates compared to their White peers. Although researchers have found these patterns across a variety of contexts, there has been little research that examines school-level mechanisms that may contribute to the high overall rates of exclusionary discipline and the attendant racial disparities. This dissertation focuses on two possible mechanisms that have been theoretically linked to increased rates of exclusionary discipline: school resource officers (SROs) and zero-tolerance approaches to discipline. Study 1 used 14 years of data from Tennessee high schools to model trends in suspension rates before and after the implementation of SROs using a latent growth curve modeling approach. The findings indicated that SRO implementation was associated with lower overall suspension rates and lower suspension rates for Black students, and no changes for White studentsâ suspension rates or racial disparities in suspension rates. Study 2 examined the relation between the combination of SROs and a high zero-tolerance approach and schoolsâ rates of exclusionary discipline using a nationally representative sample of public high schools. A series of three-way interaction models with an ordinary least squares regression framework indicated that schools that had SROs in combination with a high zero-tolerance approach to discipline had higher overall rates of exclusionary discipline in schools characterized by higher proportions of racial minority students and other indicators of disadvantage. Together, these studies suggest that SROs and zero-tolerance approaches to discipline may not be universally appropriate mechanisms for reducing rates of exclusionary discipline. Instead, school context is an important consideration when forming strategies to reduce student exclusions.

Peer multiple victimization (PMV) predicts a range of negative behavioral, psychosocial, and school-related sequela. The processes through which an adolescent who experiences PMV develops negative outcomes has received attention, but processes that mitigate the impact of these negative outcomes are largely unknown. A lack of school connectedness has been robust predictor of subsequent negative developmental outcomes, and has been demonstrated to be associated with victimization. However, competencies from the social and emotional learning framework have been linked with developing positive social connections for adolescents. This study uses a series of multilevel models to investigate whether PMV is associated with school connectedness, and whether social and emotional learning competencies affects this relation. Participants were 6,401 (47.3% Female; 36.2% White) 9th through 12th grade students from 15 schools across a large urban public school district in a southeastern state. Results suggest that PMV is associated with a lack of school connectedness and that although social and emotional competencies are particularly relevant for adolescents who experience PMV, they do not significantly buffer this relationship. Thus, adolescents who experience PMV may benefit from social and emotional competencies in spite of overwhelming evidence of associations with negative outcomes. Research, theoretical and applied implications for this vulnerable group are discussed.

Sexual minority women experience a number of physical and mental health disparities compared to their heterosexual peers. This three-paper dissertation addresses the ways in which stigma and access to care explain outcomes in sexual minority womenâs physical and mental health. The first study is a qualitative examination of sexual minority womenâs experiences of stigma, particularly related to healthcare settings. The second study is a close examination of demographic predictors of access to care among sexual minority women. The third study is an analysis of the relationship between access to care and physical and mental health outcomes among sexual minority women. Findings include in-depth information about the lived experiences of stigma within and related to healthcare settings that participants reported, identification of factors that predict access to care within this population, and models explaining a significant amount of variation in physical and mental health of sexual minority women. Together, these studies shed light on the ways in which stigma explains significant differences in wellbeing via access to adequate and effective healthcare. The findings from this dissertation can inform practice related to addressing healthcare needs of sexual minority women, policy related to health of sexual minority groups, and future research on stigma, health disparities, and access to care for sexual minority women.