Thesis (Ph. D.)--University of California, San Diego, 2007. / Title from first page of PDF file (viewed August 2, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.

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Thesis (Ph.D.)--York University, 2008. Graduate Programme in Psychology. / Typescript. Includes bibliographical references (leaves 228-251). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:NR39024

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 176-188).

Thesis (Ph.D.)--McMaster University, 2003. / Advisor: Daphne Maurer. Includes bibliographical references. Also available via World Wide Web.

Natural variability can make different instances of the same face appear remarkably dissimilar. Such variability rarely affects familiar face recognition. However, small differences in appearance between encounters can have really detrimental effects on identifying instances of unfamiliar faces as the same person. In typical face processing research, within-person variability is experimentally controlled, in order to explore the influences of between-person variability in face processing directly. That is, face stimuli are constrained so that differences between individual faces are restricted to identity-specific information; shape and texture. To this end, it remains unclear whether such natural variability plays a part in normal face processing. In this thesis, a series of experiments explore whether experiencing natural variability is beneficial in normal face processing. Specifically, the experiments described within this thesis address whether there is a role of within-person variability in face learning, with various manipulations, and also whether it has a role in improving unfamiliar face matching. The results suggest that experiencing variability is important in face learning – specifically in developing stable face representations. It was also found to be beneficial in improving unfamiliar face matching. Additional manipulations, such as the presence of additional person information, did not show any additional benefit to face learning – unlike previous studies. I suggest that the differences between the results observed here and previous studies highlight differences in measures of familiarity, and the importance of considering what different measures tell us about face processing. I discuss these findings in relation to previous face learning studies, in addition to face perception methodologies overall. Put simply, I suggest that in order to understand face identification processes comprehensively, it is important to consider both between- and within-person variability.

Face recognition is widely held to rely on 'configural processing', recently defined as an analysis of metric distances between features. Given that face recognition concerns those faces of people who we know, it is suggested that our unique representations of familiar faces contain information about these metric distances. The experiments in this thesis examine the hypothesis that face recognition relies on 'configural processing' by comparing performance between familiar and unfamiliar faces in a range of tasks. Experiments in the first half of the thesis investigate the effects of geometric distortions on different face tasks. Experiments in the second half examine familiarity advantages in rescaling distorted facial images. The main findings are that face recognition might not rely on simple measures of metric distances between features, and that observers show a surprising degree of tolerance to configural changes applied to familiar faces. This suggests that an operationalisation of configural processing will need to consider other measures that do not survive the image deformations tested in this thesis. The findings are discussed in relation to existing research on familiar face recognition as distinct from unfamiliar face perception.

Access to abstract restricted until 05/2016. / Access to thesis restricted until 05/2016. / Department of Psychological Science

This thesis used pupillometry to investigate whether pupils respond differently to faces that differ in familiarity. We aimed to see whether pupillometry measures cognitive processes involved in face processing, and whether it could be applied forensically. We started by evaluating three explanations for pupillary changes that occur when processing faces. The first was cognitive load (mental effort), because faces that have only been seen briefly are more difficult to recognise than well-known faces. The second was cognitive engagement (interest), because faces contain socially-important information. The third was memory strength (forensically applicable), as eyewitnesses have to recall a perpetrator's face in an attempt to identify them if they appear in a lineup. While pupillary responses reflected cognitive engagement to some extent, cognitive load best accounted for decreasing pupil sizes when learning new faces, and memory strength explained the pupillary changes seen in lineups. The theories all had some influence on pupil sizes, but their influence varied according to context, saliency, and the task at hand. Then we investigated whether pupillometry measured implicit recognition of a perpetrator in a lineup, and found that it did. Pupil sizes reflected memory strength in participants who believed their memory to be strong: there were differences in pupil sizes (between looking at the perpetrator and the distractors) in participants who identified him, but not in those who did not. The pupillary responses of participants who 'guessed' indicated that they were indeed guessing. There were no pupillary changes when the perpetrator was not in the lineup, even when participants misidentified a distractor. We concluded that pupillary responses are independent of explicit identification responses, and could be used forensically to support traditional measures of eyewitness identification and credibility.

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