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UBC Theses and Dissertations

The action unit imposter : head position influences social perceptions by changing the appearance of the face Witkower, Zachary


Facial structure and facial expressions play a crucial role in the communication of social information, but faces are rarely perceived in isolation. Instead, observers view faces as they rest upon their physical foundation: the head. Here, I argue that head position plays a critical role in face perception by causing the appearance of the eyebrows to change— paralleling the consequences of facial expressions— without using facial musculature. As a result, although tilting the head does not involve the activation of facial muscles, it may function as an imposter of facial muscle action by changing the appearance of the face. In the present dissertation, I test and support this broad account, and demonstrate its widespread generalizability, across 16 studies. First, in Chapter 2, I (a) provide evidence that a downwards head tilt increases perceptions of dominance, (b) demonstrate that this effect occurs by changing the apparent V-shape of the eyebrows, in particular, and (c) rule out the possibility that any of the other previously proposed mechanisms are viable explanations for observed effects. In Chapter 3, I test whether the AU imposter mechanism is likely to be a universal feature of human visual cognition, by assessing its impact on social perceptions among the Mayangna – members of an unindustrialized small-scale traditional society who have minimal exposure to North American culture. In Chapters 4 and 5 I demonstrate that the AU imposter mechanism systematically influences social perceptions of emotionally expressive faces, alongside neutral faces – including perceptions formed from expressions of anger (Chapter 4) and happiness (Chapter 5). Finally, in Chapter 6 I review the existing body of evidence in support of the AU imposter mechanism, outline theoretical and applied implications of the AU imposter, and provide avenues for future inquiry. Together, these six chapters outline how and why the head should be considered a platform for universally communicating salient interpersonal information via the face, and one that can drastically alter, and in some cases categorically change, the message communicated from both neutral and expressive faces.

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