The central goal of the current thesis was to increase our understanding of how representations of individual faces are built from instances that vary. The prototype effect was used as a tool to probe the nature of our internal face representations. In face recognition, the prototype effect refers to the tendency to recognize, or find familiar, the average image of a face after having studied a series of similar face images. The experiments presented in this thesis investigated the modulating role of different variables on the prototype effect in face recognition. In the study phase, two or more different exemplars based on the same identity were presented. In the test phase, one of the seen exemplars, the unseen prototype, and an unseen exemplar of each studied identity were presented one at a time, and participants were asked to make a recognition judgement about the prior occurrence of either the exact image or the person’s face. Variants of each face identity were either unaltered images of real people’s faces, or they were created artificially by manipulating images of faces using several different techniques. All experiments using artificial variants produced strong prototype effects. The unseen prototype image was recognized more confidently than the actually studied images. This was true even when the variants were so similar that they were barely perceptually discriminable. Importantly, even when participants were given additional exposure to the studied exemplars, no weakening of the prototype effect was observed. Surprisingly, in the experiments using natural images of real people’s faces, no clear recognition advantage for the prototype image was observed. Results suggest that the prototype effect in face recognition might not be tapping an averaging mechanism that operates solely on variations within the same identity.

Human face detection and recognition techniques play an important role in applica- tions like face recognition, video surveillance, human computer interface and face image databases. Using color information in images is one of the various possible techniques used for face detection. The novel technique used in this project was the combination of various techniques such as skin color detection, template matching, gradient face de- tection to achieve high accuracy of face detection in frontal faces. The objective in this work was to determine the best rotation angle to achieve optimal detection. Also eye and mouse template matching have been put to test for feature detection.

Thesis (Ph. D.)--University of California, San Diego, 2007. / Title from first page of PDF file (viewed January 14, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references. Faces are central stimuli in our everyday life, hence, face processing is a sophisticated and highly specialized cognitive ability, at which adults are experts and children are proficient. Unlike other visuospatial abilities, face perception develops very slowly, becoming adult-like only well into adolescence. Some performance disparities between children and adults may reflect differences in general cognitive abilities, such as attention and memory. Alternatively, performance differences can be attributed to specific cognitive strategies implemented during face processing by different age groups; or to the interaction between the improvement of general abilities throughout development and the refinement of face specific cognitive strategies. The intent of the current studies was to further assess the development of and relationship between cognitive strategies in face processing. Specifically, we investigated the behavior and neurocorrelates associated with holistic face processing in children (8- to 11-year-olds), adolescents, and adults, utilizing the composite face effect. The task requires participants to engage in both holistic and featural processing, but certain trials (aligned-same) elicit a visual illusion called the composite face effect (CFE, calculated as difference between misaligned-same and aligned-same trials), which is considered an index of holistic processing. All age groups (adults, adolescents, 8- to 9-year-olds, 10- to 11-year-olds) showed a CFE, suggesting reliance on holistic processing. Notably, about half of the 8- to 11-year-old children displayed adult-like behavior and adult-like CFE, suggesting their reliance on holistic processing. However, the other half of the children performed below-chance on aligned-same trials, displayed an extremely large CFE, and a significant difference between different trials, suggesting reliance on a featural strategy. Thus child age groups were regrouped according to their accuracy performance on the hardest condition (aligned-same trials) into high performing and low performing children. We hypothesize that the aligned-same trials were too taxing for low-performing children, thus they fell back into relying on simpler strategies such as a difference-detection featural strategy. In order to further investigate the CFE behavioral differences between age and performance groups, we completed an imaging study. For the fMRI study children were grouped by performance rather than age following the results of our behavioral study. Overall, our imaging results for the CFE, thus for holistic processing, resembled behavioral results in that adult and high performing child groups revealed a similar (but not identical) whole-brain pattern of activation, whereas the low performing child group showed a distinctive pattern of activation for the composite face effect. Adults and high performing children showed a pattern of activation spanning frontal, parietal, temporal, and occipital lobes. In contrast, low performing children revealed a pattern of activation that spanned frontal, temporal, cingulate, and cerebellar regions. Brain areas typically associated with face processing, such as the right fusiform gyrus and right inferior temporal gyrus did not reach significance for the low performing child group. These differences may be attributable to the use of different cognitive strategies. However, the extent of frontal and cingulate cortex activation in low performing children may also suggest that because the task was especially difficult for them, working memory resources were particularly taxed, thus affecting the neural network engaged. Importantly, not only were performance differences associated with distinct neurocorrelates (i.e., differing profiles for low performing children vs. high performing children and adults), but age differences also had an appreciable effect. In fact, high performing children did not significantly differ from adults in the behavioral CFE, but did show differences in the neural CFE.

Thesis (M.S.W.)--Smith College School for Social Work, Northampton, Mass., 2007 / Thesis submitted in partial fulfillment for the degree of Master of Social Work. Includes bibliographical references (leaves 69-72).

Thesis (M.S.)--University of Michigan, 1969.

Thesis (M.S.)--University of Michigan, 1970.

Thesis (M.S.)--University of Michigan, 1967.

Thesis (M.S.)--University of Michigan, 1988.

Thesis (M.S.)--University of Michigan, 1969.

Thesis (M.S.)--University of Michigan, 1988.