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Anxiety disorders commonly emerge during adolescence, and girls are diagnosed with these disorders more frequently than boys. Understanding why anxiety disorders emerge and why non-clinical anxiety symptoms increase during adolescence is important for understanding this sex difference and how to treat adolescent sufferers. Potential mechanisms, such as puberty or cognitive biases, can be investigated both in humans and in rodent models of anxiety. This thesis aimed to characterise sex differences and changes in anxiety-like behaviour across adolescence and into adulthood in the rat, and to examine anxiety and interpretive bias in adolescent humans. In rats, we examined performance on common tests of anxiety-like behaviour: the emergence test, open field and elevated plus-maze. Exploration on these tests increased from mid-adolescence into adulthood, and greater exploration by females was apparent from late adolescence. While the behaviours themselves remain interesting, caution on interpreting these behaviours as anxiety-related warranted and is discussed throughout the thesis. Potential effects of the ovarian cycle and testing order on EPM performance were also examined. In humans, 12-14 year old adolescents complete visual and written interpretive bias tasks, this bias being considered to be a cognitive vulnerability for anxiety. The results showed that, when imagining themselves in ambiguous scenarios, girls were more negative in their interpretations than boys. Additionally, both sexes also interpreted social scenarios more negatively than non-social scenarios. As puberty is thought to be important to the emergence of disorder during adolescence, interpretive bias could potentially mediate the puberty-anxiety relationship. While more interpretive bias work is needed in both species, the recent development of interpretive bias tasks for rodents provides an opportunity to move away from difficult to interpret tests of anxiety-like behaviour in rodents, and should allow for greater convergence of the human and rodent anxiety research.

[Truncated abstract] It is well established that anxiety vulnerability is characterised by two biased patterns of selective information processing (Mathews & MacLeod, 1986; Mogg & Bradley, 1998). First anxiety is associated with an attentional bias, reflecting the selective allocation of attention to threatening stimuli in the environment (Mathews & MacLeod, 1985; MacLeod, Mathews & Tata, 1986; MacLeod & Cohen, 1993). Second anxiety is associated with an interpretive bias, reflecting a disproportionate tendency to resolve ambiguity in a threatening manner (Mogg et al., 1994). These characteristics are shown by normal individual high in trait anxiety (Mathews, Richards & Eysenck, 1989; Mogg, Bradley & Hallowell, 1994; Mathews & MacLeod, 1994), and by examining clinically anxious patients who repeatedly report elevated trait anxiety levels (MacLeod, Mathews & Tata, 1986; Mogg & Bradley, 1998). '...' Two alternative hypotheses regarding this relationship are proposed. One hypothesis is that attentional and interpretive biases are concurrent expressions of a single underlying biased selectivity mechanism that characterises anxiety vulnerability (the Common Mechanism account). In contrast, a quite different hypothesis is that attentional and interpretive biases are independent cognitive anomalies that represent separate pathways to anxiety vulnerability (the Independent Mechanisms account). The present research program was designed to empirically test the predictions that differentiate the Common Mechanism and Independent Mechanisms accounts. The general methodological approach that was adopted was to employ bias manipulation tasks from the literature that have been developed and validated to directly modify one class of processing bias (i.e. attentional bias or interpretive bias). The effect of these direct bias manipulation tasks on a measure of the same class of processing bias or the other class of processing bias was then examined. The Common Mechanism and Independent Mechanisms accounts of the relationship between attentional and interpretive bias generate differing predictions concerning the impact of directly manipulating one class of processing bias upon a measure of the other class of processing bias. The central difference between the alternate accounts is their predictions regarding cross-bias transfer, that is the transfer of training effects from direct manipulation of one class of processing bias to a measure of the other class of processing bias. Whereas the Common Mechanism account predicts that such cross-bias transfer will occur, the Independent Mechanisms account does not predict such transfer. A series of seven studies is reported in this thesis. There was some difficulty achieving successful bias modification using bias manipulation approaches established in the literature; however when such manipulation was achieved no cross-bias transfer was observed. Therefore the obtained pattern of results was consistent with the Independent Mechanisms (IM) account, and inconsistent with the Common Mechanism (CM) account. A more detailed version of the IM account is developed to more fully accommodate the specific results obtained in this thesis.

Child and adolescent mood and anxiety symptoms are common and debilitating, with long-term effects on well-being. Research presented in this thesis examines interpersonal cognitive factors in the emergence of anxious and depressive symptoms in late childhood through to early adulthood. The thesis considers this issue using three main approaches. For the first, data are presented showing that biases in the appraisals of social situations are the aspects of interpersonal cognition most closely associated with emotional symptoms. For the second, longitudinal twin data are used to examine genetic and environmental origins of these interpersonal cognitive biases and their temporal prediction of symptoms across a 2-year period. Data show that interpersonal cognitive factors are strongly influenced by non-shared environmental factors, and moreover, predict symptoms across time. The final section of the thesis comprises four studies using Cognitive Bias Modification of Interpretations (CBM-I) training methodology to show that both positive and negative interpretive biases for interpersonal information can be induced in adolescents. Positive biases are shown to persist for at least 24 hours after training, and induced positive and negative biases are shown to differentially predict anxious responses to an experimental stressor. Evidence is also provided to suggest that effects following training positive interpretive biases may transfer to other cognitive measures, namely appraisals of ambiguous emotional faces. Finally, data tentatively show that CBM-I training may be useful in reducing negative interpretations of interpersonal information made by 11-year-old children undergoing the transition to secondary school. In summary, studies in this thesis support the contribution of cognitive biases to mood and anxiety symptoms in childhood and adolescence. They further extend this knowledge by suggesting that these reflect individual-specific (non-shared) environmental risks to predict symptoms across time. These biases may also be amenable to change through training interventions, with some - albeit weak - effects on other cognitive outcomes.

Tous les jours, dans le monde, des comportements agressifs sont commis à l’égard d’individus, causant des préjudices physiques, psychologiques et financiers. En réponse à une provocation, ces agressions sont dites réactives et peuvent être alimentées par des biais cognitifs d’attribution d’intention hostile et des styles de personnalité antisociale. Comblant un trou dans la littérature scientifique, cette étude a pour but d’évaluer le biais d’attribution d’intention hostile ainsi que son rôle dans la relation entre la personnalité antisociale et l’agressivité réactive. Dans cette perspective, les participants étaient invités à répondre à des questionnaires évaluant la personnalité, les processus cognitifs et l’agressivité. Puis, pendant l’enregistrement de leur activité cérébrale, ils devaient lire des scénarios d’interactions sociales et attribuer une intention aux comportements décrits comme ambigus et provocateurs. Nous avons analysé la N400, une composante de potentiels reliés aux évènements, associée à la présentation d’intentions inattendues hostiles ou non hostiles après chaque scénario. Des analyses de corrélations de Pearson et de régressions linéaires multiples ont été réalisées pour examiner la validité de notre modèle de médiation. Les résultats montrent que la N400 est plus forte lors de la présentation d’intention non hostile inattendue que lors de la présentation d’intention hostile inattendue dans les régions centropariétales. La personnalité antisociale et la violation des attentes hostiles étaient reliées positivement à l’agressivité réactive. La personnalité antisociale prédisait l’agressivité réactive même à l’ajout de la violation des attentes hostile (Z = .30, p = .76) ou de la violation des attentes non hostiles (Z = -.32, p = .75) comme médiateur. En somme, le rôle médiateur du biais d’attribution d’intention n’est pas confirmé et d’autres études sont nécessaires pour mieux comprendre le lien entre la personnalité antisociale et l’agressivité réactive. / Every day, around the world, aggressive behaviors are committed against individuals, causing physical, psychological and financial harm. In response to provocation, these assaults are said to be reactive and can be fuelled by cognitive biases of attributing hostile intent and antisocial personality styles. Filling a gap in the scientific literature, the purpose of this study is to evaluate hostile intent bias and its role in the relationship between antisocial personality and reactive aggression. To this end, participants were asked to complete questionnaires assessing personality, cognitive processes and aggression. Then, while recording their brain activity, they were asked to read scenarios of social interactions and to attribute intent to behaviors described as ambiguous and provocative. We analyzed the N400, an event-related potential component associated with the presentation of unexpected hostile or non-hostile intentions after each scenario. Pearson correlation and multiple linear regression analyses were performed to examine the validity of our mediation model. The results show that the N400 is stronger in the presentation of unexpected non-hostile intent than in the presentation of unexpected hostile intent in the centro-parietal regions. Antisocial personality and violation of hostile expectations were positively related to reactive aggression. Antisocial personality predicted reactive aggression even with the addition of hostile expectation violation (Z = .30, p = .76) or non-hostile expectation violation (Z = -.32, p = .75) as a mediator. In sum, the mediating role of intention attribution bias is unconfirmed and further studies are needed to better understand the link between antisocial personality and reactive aggression.