[Truncated abstract] One aim of the present research program was to investigate motivational response inclinations toward high-caloric food at implicit and explicit processing levels with unipolar measures to account for ambivalence. A second aim was to examine the extent of the influence of these implicit and explicit processes on unhealthy eating behaviors, and specifically investigate why people reporting avoid motivational inclinations continue to indulge in high-fat foods. The aim of Study 1 was to examine discordance between implicit and explicit attitudes toward high-fat food in groups that differed in preference for high-fat food. Using a bipolar version of the Implicit Association Test (IAT), a group difference was found in implicit attitudes toward high-fat food with a trend toward concordance. The aims of Study 2 were to examine if concordance between implicit and explicit processes would be greater if one accounted for motivational ambivalence within and between implicit and explicit processing levels, and to test the influence of these processes on food choice behavior. Using a unipolar version of the IAT, a pattern of concordance was found between implicit and explicit inclinations in most participants, except for those reporting weak avoid and strong approach inclinations. Further, implicit avoid and explicit avoid inclinations were found to predict food choice behavior in a context that made body and weight concerns salient. A parallel study (Study 3) was conducted with a high-caloric food that is viewed very ambivalently by society (i.e., chocolate) to determine if societal ambivalence is reflected in implicit associations, and to test the influence of implicit and explicit processes on food choice behavior. In contrast to Study 2, results indicated that all groups were implicitly ambivalent toward chocolate. Further, implicit approach and explicit avoid inclinations were found to antagonistically predict behavior suggesting that the proximal benefits of chocolate indulgence tend to outweigh the distal consequences. ... Results showed that when the unhealthy consequences of high-fat food consumption were primed, implicit avoid motivational inclinations toward high-fat food could be differentially activated and influence choice of certain high-fat foods. In conclusion, this research program found evidence for eating-related ambivalence within and between implicit and explicit processing levels which underscores the importance of utilizing unipolar measures in research investigating motivational response inclinations toward food and other substances. Further, implicit and explicit processes were found to influence high-fat food choice behavior in an antagonistic pattern with implicit approach inclinations conflicting with explicit avoid inclinations when health and weight concerns were not salient, providing support for the additive predictive pattern of food choice. A key theoretical implication of this research program is that the integration of the dual process models (e.g., Strack & Deutsch, 2004) with the ambivalence model of substance craving (e.g., Breiner, Stritzke, & Lang, 1999) can advance the understanding of competing motivational response inclinations toward high-fat foods at the implicit and explicit levels.

Les postures corporelles signalant domination ou soumission servent une fonction de communication chez les humains et d’autres animaux. La question de savoir si l'adoption de telles "postures de pouvoir" influence la perception et le comportement de l'agent fait actuellement l'objet d'un débat. Le travail réalisé pendant cette thèse consistait à explorer les effets de ces postures sur des comportements étroitement liés à leur fonction primaire, à savoir la communication sociale, en se focalisant sur les réponses aux visages, signaux sociaux particulièrement saillants. Dans une série d'expériences, j'ai utilisé des méthodes de corrélation inverse pour visualiser les représentations mentales de traits préférés du visage. Les représentations mentales des visages préférés implicitement et explicitement évoquaient une impression affiliative et légèrement dominante, mais ne révélaient aucun effet reproductible des postures. Deux autres expériences distinctes ont étudié les effets de la posture sur la perception d’expressions faciales menaçantes et sur les comportements d'approche ou d'évitement en réponse à ces signaux. Bien que les postures n'aient pas d’influence sur la reconnaissance explicite d’expressions faciales menaçantes, elles ont un impact sur les décisions d'approcher ou d'éviter des signaux de menace. Plus précisément, l'adoption d'une posture de soumission augmentait la tendance à éviter les personnes exprimant la colère. Enfin, une tentative de réplication des effets des postures sur les niveaux de testostérone et de cortisol a démontré que même l'adoption répétée d'une posture de pouvoir en contexte social ne provoque pas de changements hormonaux. Dans l'ensemble, ces résultats suggèrent que notre posture corporelle n’influence pas nos représentations mentales et notre perception des autres individus, mais pourrait influencer nos actions en réponse aux signaux sociaux. / Expansive and constrictive body postures serve a primary communicative function in humans and other animals by signalling power and dominance. Whether adopting such “power postures” influences the agent’s own perception and behaviour is currently a subject of debate. In this PhD thesis, I explored effects of adopting power postures on behaviours closely related to the postures’ primary function of social signalling by focusing on responses to faces as particularly salient social signals. In a series of experiments, I utilized reverse correlation methods to visualize mental representations of preferred facial traits. Mental representations of implicitly as well as explicitly preferred faces evoked an affiliative and slightly dominant impression, but revealed no replicable effects of power postures. Two further separate experiments investigated posture effects on the perception of threatening facial expressions, and approach vs. avoidance actions in response to such social signals. While postures did not influence explicit recognition of threatening facial expressions, they affected approach and avoidance actions in response to them. Specifically, adopting a constrictive posture increased the tendency to avoid individuals expressing anger. Finally, an attempt to replicate posture effects on levels of testosterone and cortisol demonstrated that even repeatedly adopting a power posture in a social context does not elicit hormonal changes. Altogether, these findings suggest that our body posture does not influence our mental representations and perception of other people’s faces per se, but could influence our actions in response to social signals.