Sexual selection and the human face : beauty in the face of the beheld and in the eye of the beholder
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Evolutionary theory has been proposed to provide an answer to the question of why some faces are perceived to be more attractive than others are. The first part of this thesis provides an introduction to an evolutionary approach to studying attractiveness (Chapter 1) and reviews sexual selection theory (Chapter 2) and how this theory has been applied to help understand human facial attractiveness (Chapter 3). The thesis focuses particularly on symmetry and secondary sexual characteristics in faces, two of the main factors that relate to attractiveness from an evolutionary perspective as they are both proposed to be associated with genetic benefits to the choosing individual. The empirical work in the first part of the thesis is consistent with both masculinity and symmetry in males reflecting adaptive selection for high quality mates. Facial masculinity was found to be associated with personality attributions that appear consistent with masculinity reflecting testosterone level in males. Masculinity was associated with some negative personality attributions and when controlling for such attributions masculinity in male faces was found to be of increased attractiveness (Chapter 4). Facial symmetry was found to be preferred in opposite-sex faces by both males and females when images were presented upright and less so when the images were inverted (Chapter 5). Symmetry was also found to be preferred in familiar faces and both this preference and preferences differing according orientation are consistent with the notion that symmetry preferences are an adaptation to identify high quality mates. The second part of this thesis presents views on the existence of individual differences in attractiveness judgements that are consistent with evolutionary theory. Evidence is reviewed regarding how individual differences in preference could be more adaptive than a single species wide strategy (Chapter 6). Chapters 7 and 8 present studies showing that preferences for sexual dimorphism and symmetry differ between women in ways that may have been adaptive over evolutionary time. Women who are attractive prefer higher levels of masculinity and symmetry than less attractive women (Chapter 7) and women judging for short-term relationships or women who already have current partners prefer more masculinity in male faces than those judging for long-term relationships or women who do not have a partner (Chapter 8). Chapter 9 again shows that individual differences in mate-choice do exist and can be consistent with evolutionary theory showing that individuals choose partners resembling their opposite-sex parent, a phenomenon that may reflect imprinting-like effects in humans. This thesis presents data that is consistent with the notion that sexual dimorphism and symmetry may advertise quality in human faces (Part 1) and data on several potentially adaptive individual differences in human face preferences (Part 2). Individuals can both agree, on average, on what is attractive and unattractive and yet still demonstrate variation in judgements. In this way beauty can be said to be both in the face of the beheld and in the eye of beholder.
Thesis, PhD Doctor of Philosophy
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