Pages ii, iv, vi and viii are blank, therefore omitted. / <p>Faces are often deemed special objects because they are associated with behavioural and physiological characteristics that differ from those of other objects. These characteristics may indicate that faces are processed with separate mechanisms than other objects. On the other hand, these characteristics may be the result of our extensive experience with faces. If so, other objects should exhibit these same characteristics with sufficient exposure. This prediction has begun to be addressed both from studies of real-world experts and from studies that explicitly manipulate experience with non-face objects in the lab.</p><p>Contributing to this larger framework, here we demonstrate that : (1) large inversion effects can be obtained through training alone, therefore large face inversion effects are insufficient evidence of specialized face-processing mechanisms; (2) house-identification training substantially improves behavioural performance but has minimal impact on fMRI activity recorded in areas that preferentially respond to houses or faces, nor in retinotopically-defined early visual areas. (3) house-identification training systematically reduces the amplitude of late ERP components in the range of 200-300 ms, and (4) the relative patterns of ERP responses to faces and houses remain quite stable after houseidentification training, with faces continuing to exhibit larger, earlier Nl responses than houses.</p><p>Together, these results suggest that, although some behavioural characteristics attributed to specialized face processing can be adequately explained through experience alone, training of non-face objects does not readily reduce existing differences in the fMRI and EEG signatures of face and object processing.</p> / Thesis / Doctor of Philosophy (PhD)

Missing pages were blank, therefore omitted. / Practice improves sensory perception, a phenomenon known as perceptual learning. Perceptual learning is interesting because it reflects plasticity in the brain where none was imagined, and because of its enormous applied potential. In vision, learning of simple discriminations is well-described. Here, I study the learning of two complex visual tasks, texture-and face identification, using a ten-alternative forced-choice procedure. The data are clear: learning of complex patterns is much like learning of simple patterns in its specificity, stability and time-course. Therefore, learning obeys similar rules at several levels in visual processing. The characteristics of learning, in particular the specificity and stability of learning, affect inherent aspects of object recognition. / Thesis / Doctor of Philosophy (PhD)

Individuals perceive emotional facial expressions in categories. Specifically, for basic emotional expressions, discrimination performance is better for pairs of stimuli that fall in either side of a perceptual category boundary than for those within a perceptual category. In this thesis I have examined categorical perception of emotional facial expressions from a number of different perspectives. In Chapter 2, I found in two experiments that categorical perception of emotional facial expressions of a robust phenomenon with a few consistent individual differences. There findings highlight some of the important caveats that categorical perception researchers face, not only in the area of emotional facial expressions, but across domains as well. In Chapter 3 I show that context has an effect on the visual perception of emotional facial expressions. A surprise-fear continuum was perceived categorically only in the case in which a context story was provided for the surprise face. In Chapter 4 I demonstrate categorical perception of a happy-sad continuum in 3.5-year-olds. This is an important study in development because the current literature is limited by studies that do not compare identification and discrimination performance in these age groups. The experiment in this chapter uses both identification and discrimination tasks and compares the results of 3.5-year-olds to adults who do the exact same task. The results suggest that 3.5-year-olds perceive happy and sad expressions as adults do, categorically. In Chapter 5 I develop a powerful new methodology for the study of the category boundary using non-verbal methods. This investigation with emotional facial expressions shows it can be reliably used to identify category boundary information in adults. Perception of emotional facial expressions is an essential part of successful social cognition, and the phenomenon of categorical perception specifically allows individuals to quickly and accurately respond to expressions. The research in this thesis is a further step in understanding the processes that allows individuals to be successful in a social environment. / Thesis / Doctor of Philosophy (PhD)