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There has recently been much interest in how limitations in spatial frequency range affect face and object perception. This work has mainly focussed on determining which bands of frequencies are most useful for visual recognition. However, a fundamental question not yet addressed is how spatial frequency overlap (i.e., the range of spatial frequencies shared by two images) affects complex image recognition. Aside from the basic theoretical interest this question holds, it also bears on research about effects of display format (e.g., line-drawings, Mooney faces, etc.) and studies examining the nature of mnemonic representations of faces and objects. Examining the effects of spatial frequency overlap on face and object recognition is the main goal of this thesis. / A second question that is examined concerns the effect of calibration of stimuli on recognition of spatially filtered images. Past studies using non-calibrated presentation methods have inadvertently introduced aberrant frequency content to their stimuli. The effect this has on recognition performance has not been examined, leading to doubts about the comparability of older and newer studies. Examining the impact of calibration on recognition is an ancillary goal of this dissertation. / Seven experiments examining the above questions are reported here. Results suggest that spatial frequency overlap had a strong effect on face recognition and a lesser effect on object recognition. Indeed, contrary to much previous research it was found that the band of frequencies occupied by a face image had little effect on recognition, but that small variations in overlap had significant effects. This suggests that the overlap factor is important in understanding various phenomena in visual recognition. Overlap effects likely contribute to the apparent superiority of certain spatial bands for different recognition tasks, and to the inferiority of line drawings in face recognition. Results concerning the mnemonic representation of faces and objects suggest that these are both encoded in a format that retains spatial frequency information, and do not support certain proposed fundamental differences in how these two stimulus classes are stored. Data on calibration generally shows non-calibration having little impact on visual recognition, suggesting moderate confidence in results of older studies.

Current models of face perception suggest independent processing of identity and expression, though this distinction is still unclear. Using converging methods of psychophysics and functional magnetic resonance imaging (fMRI) in healthy and patient populations we assessed the relationship between these two perceptual processes. First, using perceptual aftereffects, we explored the neural representations underlying identity and expression. The expression aftereffect only partially transferred across different identities, suggesting adaptation within identity-invariant and identity-dependent expression representations. Contrarily, the identity aftereffect fully transferred across different expressions. This asymmetry cannot be explained through low-level adaptation. The identity-dependent component of the expression aftereffect relies on adaptation to a coherent expression, not low-level features, in the adapting face. Thus adaptation generating the expression aftereffect must occur within high-level representations of facial expression. Second, using fMRI adaptation, we examined identity and expression sensitivity in healthy controls. The fusiform face area and posterior superior temporal sulcus showed sensitivity for both identity and expression changes. Independent sensitivity for identity and expression changes was observed in the precuneus and middle superior temporal sulcus respectively. Finally, we explored identity and expression perception in a neuropsychological population. Selective identity impairments were associated with inferior occipitotemporal damage, not necessarily affecting the occipital or fusiform face areas. Impaired expression perception was associated with superior temporal sulcus damage, and also with deficits in the integration of identity and expression. In summary, psychophysics, neuroimaging and neuropsychological methods all provide converging evidence for the independent processing of identity and expression within the face network. However, these same methods also supply converging evidence for a partial dependence of these two perceptual processes: in the expression aftereffect, the functional sensitivities of the FFA and pSTS, and identity deficits observed in a patient with primarily impaired expression perception and a spared inferotemporal cortex. Thus, future models of face perception must incorporate representations or regions which independently process identity or expression as well as those which are involved in the perception of both identity and expression.

Two connectionist models are developed that predict humans' categorization of facial expressions of emotion and their judgements of similarity between two facial expressions. For each stimulus, the models predict the subjects' judgement, the entropy of the response, and the mean response time (RT). Both models involve a connectionist component which predicts the response probabilities and a response generator which predicts the mean RT. The input to the categorization model is a preprocessed picture of a facial expression, while the hidden unit representations generated by the first model for two facial expressions constitute the input of the similarity model. The data collected on 45 subjects in a single-session experiment involving a categorization and a similarity task provided the target outputs to train both models. Two response generators are tested. The first, called the threshold model , is a linear integrator with threshold inspired from Lacouture and Marley's (1991) model. The second, called the channel model, constitutes a new approach which assumes a linear relationship between entropy of the response and mean RT. It is inspired by Lachman's (1973) interpretation of Shannon's (1948) entropy equation. The categorization model explains 50% of the variance of mean RT for the training set. It yields an almost perfect categorization of the pure emotional stimuli of the training set and is about 70% correct on the generalization set. A two-dimensional representation of emotions in the hidden unit space reproduces most of the properties of emotional spaces found by multidimensional scaling in this study as well as in other studies (e.g., Alvarado, 1996). The similarity model explains 53% of the variance of mean similarity judgements; it provides a good account of subjects' mean RT; and it even predicts an interesting bow effect that was found in subjects' data.

Students with learning disabilities (LD) have been found to exhibit social difficulties compared to those without LD (Wong, 2004). Recognition, expression, and understanding of facial expressions of emotions have been shown to be important for social functioning (Custrini & Feldman, 1989; Philippot & Feldman, 1990). LD subtypes have been studied (Rourke, 1999) and children with nonverbal learning disabilities (NVLD) have been observed to be worse at recognizing facial expressions compared to children with verbal learning disabilities (VLD), no learning disability (NLD; Dimitrovsky, Spector, Levy-Shiff, & Vakil, 1998; Dimitrovsky, Spector, & Levy-Shiff, 2000), and those with psychiatric difficulties without LD controls (Petti, Voelker, Shore, & Hyman-Abello, 2003). However, little has been done in this area with adolescents with NVLD. Recognition, expression and understanding facial expressions of emotion, as well as general social functioning have yet to be studied simultaneously among adolescents with NVLD, NLD, and general learning disabilities (GLD). The purpose of this study was to examine abilities of adolescents with NVLD, GLD, and without LD to recognize, express, and understand facial expressions of emotion, in addition to their general social functioning. / Adolescents aged 12 to 15 were screened for LD and NLD using the Wechsler Intelligence Scale for Children---Third Edition (WISC-III; Weschler, 1991) and the Wide Range Achievement Test---Third Edition (WRAT3; Wilkinson, 1993) and subtyped into NVLD and GLD groups based on the WRAT3. The NVLD ( n = 23), matched NLD (n = 23), and a comparable GLD (n = 23) group completed attention, mood, and neuropsychological measures. The adolescent's ability to recognize (Pictures of Facial Affect; Ekman & Friesen, 1976), express, and understand facial expressions of emotion, and their general social functioning was assessed. Results indicated that the GLD group was significantly less accurate at recognizing and understanding facial expressions of emotion compared to the NVLD and NLD groups, who did not differ from each other. No differences emerged between the NVLD, NLD, and GLD groups on the expression or social functioning tasks. The neuropsychological measures did not account for a significant portion of the variance on the emotion tasks. Implications regarding severity of LD are discussed.

When viewing a face, healthy individuals tend to fixate on upper regions, particularly the eyes, which provide important configural information about the spatial layout of the face. In contrast, individuals with face blindness (prosopagnosia) rely more on local features – particularly the mouth. Presented here is an examination of face perception deficits in individuals with Posterior Cortical Atrophy (PCA). PCA is a rare progressive neurodegenerative disorder that is characterized by atrophy in occipito-parietal and occipito-temporal areas. PCA primarily affects higher visual processing, while memory, reasoning, and insight remain relatively intact. Common among individuals with PCA is simultanagnosia, an inability to perceive more than one object or detail simultaneously. One might consider simultanagnosia the most extreme form of a feature-based approach. In a series of investigations, individuals with PCA and their healthy control participants completed a same/different discrimination task in which images of faces were presented as cue-target pairs. Eye-tracking equipment (Experiment 1) and the newly developed Viewing window paradigm (Experiment 2) were used to investigate scanning patterns when faces were presented in full view, and through a restricted viewing aperture, respectively. In contrast to previous prosopagnosia research, individuals with PCA each produced unique scan paths that focused on one aspect of the face. Individuals with PCA tended to focus on areas of high-contrast but many of these areas were not diagnostically useful, suggesting that they were having difficulty processing the face even at a featural level. These results suggest a role of simultanagnosia in the scan patterns of PCA patients that is not reflective of ‘typical’ prosopagnosia, and instead points to simultanagnosia, sometimes matched with basic perceptual impairments, as a significant contributor to the face perception deficits seen in PCA.

The present study investigated hemispheric lateralization and the use of serial versus global processing of facial stimuli in a recognition task. The subjects were 19 male and 29 female undergraduate students. Identi-Kit faces which varied on four features (hair, eyes, mouth, and chin) were tachistoscopically presented. The accuracy of the subjects' responses were recorded. Analyses of variance suggested that subjects did not differ in use of inner or outer details, but did differ in use of upper and lower details. The data suggested a top-to-bottom order of processing for stimuli presented in both visual fields, with the most accurate recognition based on the hair, eyes, mouth, and chin, in that order.

When viewing a face, healthy individuals tend to fixate on upper regions, particularly the eyes, which provide important configural information about the spatial layout of the face. In contrast, individuals with face blindness (prosopagnosia) rely more on local features – particularly the mouth. Presented here is an examination of face perception deficits in individuals with Posterior Cortical Atrophy (PCA). PCA is a rare progressive neurodegenerative disorder that is characterized by atrophy in occipito-parietal and occipito-temporal areas. PCA primarily affects higher visual processing, while memory, reasoning, and insight remain relatively intact. Common among individuals with PCA is simultanagnosia, an inability to perceive more than one object or detail simultaneously. One might consider simultanagnosia the most extreme form of a feature-based approach. In a series of investigations, individuals with PCA and their healthy control participants completed a same/different discrimination task in which images of faces were presented as cue-target pairs. Eye-tracking equipment (Experiment 1) and the newly developed Viewing window paradigm (Experiment 2) were used to investigate scanning patterns when faces were presented in full view, and through a restricted viewing aperture, respectively. In contrast to previous prosopagnosia research, individuals with PCA each produced unique scan paths that focused on one aspect of the face. Individuals with PCA tended to focus on areas of high-contrast but many of these areas were not diagnostically useful, suggesting that they were having difficulty processing the face even at a featural level. These results suggest a role of simultanagnosia in the scan patterns of PCA patients that is not reflective of ‘typical’ prosopagnosia, and instead points to simultanagnosia, sometimes matched with basic perceptual impairments, as a significant contributor to the face perception deficits seen in PCA.

When a witness views a crime, they are often asked to construct a facial likeness, or composite of the suspect. These composites are then used to stimulate recognition from someone who is familiar with the suspect. Facial composites are commonly used in large scale cases e. g. Jill Dando, Yorkshire Ripper, however a great deal of research has indicated that facial composites perform poorly and often do not portray an accurate likeness of the suspect. This thesis therefore examined methods of improving facial composites. In particular, it examined methods of increasing the likeness portrayed in composites, both during construction and at test. Experiments 1 to 3 examined the effectiveness of a new three-quarter-view database in PROfit. Experiment 1 examined whether the presentation of composites in a three-quarter- view composite will aid construction. Participant-witnesses were exposed to all views of a target and the results indicated that three-quarter-view composites performed as well as full-face composites but not better. Experiments 2 and 3 then examined whether the presentation of two composites (one in a full-face view and the other in a three-quarter-view) from the same participant-witness would increase performance above the level observed for a single composite. The results revealed that two views were better than one. In addition, experiment 3 examined the issue of encoding specificity and viewpoint dependency in composite construction. All participant-witnesses were exposed to either one view of a target (full-face or three-quarter) or all views and they were asked to construct both a full-face and a three-quarter- view composite. The results indicated that performance was better when all views of a face had been presented. When a target had been seen in a three-quarter-view, it was better to construct a three-quarter-view composite. However, when a target had been seen in a full-face view, performance for both full-face and three-quarter composites was poor. Experiments 4 to 8 examined whether the presentation of composites from multiple witnesses would increase performance. The results revealed that morphing composites from four different witnesses (4-Morphs) resulted in an image that performed as well as or better than the best single image. Further experimentation attempted to examine why multiple composites performed well. In particular, it was asked whether multiple composites performed well because they contained varied information or whether they performed well because they just contained more information. Multiple composites from both single and multiple witnesses using the same (PROfit) and different (PROfit, E-FIT, Sketch, EvoFIT) composite techniques were compared and the results revealed that multiple composites performed well because they contained different memorial representations. This combination of different memorial representations appeared to result in an image that was closer to the ideal, or prototypical image. Experiments 9 to 12 examined the relationship between verbal descriptions and composite quality. The results revealed that there was no clear relationship between the amount of description provided, the accuracy of the description and performance of the resulting composite. Further experimentation examined whether the presentation of a composite and a description would increase performance above the level observed for a single composite. The results revealed that the combination of a description and a composite from the same participant-witness did increase performance. This indicated that descriptions and composites might contain differing amounts and types of featural and configurational information. Both the theoretical and practical implications of these results are discussed. Experiments 1, 2 and 3 of this thesis have been submitted for publication. Ness, H., Hancock, P. J. B., Bowie, L. and Bruce, V. Are two views better than one? A study investigating recognition of full-face and three-quarter-view composites. Applied Cognitive Psychology. Experiment 4 of this thesis appears in Bruce, V., Ness, H., Hancock, P. J. B., Newman, C. and Rarity, J. (2002). Four heads are better than one: combining face composites results yields improvements in face likeness. Journal of Applied Psychology. 87 (5), 894-902. Other Publications Frowd, C. D., Carson, D., Ness, H., Richardson, J., Morrison, L., McLanaghan, S., Hancock, P. J. B. Evaluating Facial Composite Systems. Manuscript accepted for publication in Psychology, Crime and Law. Frowd, C. D., Carson, D., Ness, H., McQuiston, D., Richardson, J., Baldwin, H., Hancock, P. J. B. Contemporary Composite Techniques: The impact of a forensically relevant target delay. Manuscript accepted for publication in Legal and Criminological Psychology.

Current models of face perception suggest independent processing of identity and expression, though this distinction is still unclear. Using converging methods of psychophysics and functional magnetic resonance imaging (fMRI) in healthy and patient populations we assessed the relationship between these two perceptual processes. First, using perceptual aftereffects, we explored the neural representations underlying identity and expression. The expression aftereffect only partially transferred across different identities, suggesting adaptation within identity-invariant and identity-dependent expression representations. Contrarily, the identity aftereffect fully transferred across different expressions. This asymmetry cannot be explained through low-level adaptation. The identity-dependent component of the expression aftereffect relies on adaptation to a coherent expression, not low-level features, in the adapting face. Thus adaptation generating the expression aftereffect must occur within high-level representations of facial expression. Second, using fMRI adaptation, we examined identity and expression sensitivity in healthy controls. The fusiform face area and posterior superior temporal sulcus showed sensitivity for both identity and expression changes. Independent sensitivity for identity and expression changes was observed in the precuneus and middle superior temporal sulcus respectively. Finally, we explored identity and expression perception in a neuropsychological population. Selective identity impairments were associated with inferior occipitotemporal damage, not necessarily affecting the occipital or fusiform face areas. Impaired expression perception was associated with superior temporal sulcus damage, and also with deficits in the integration of identity and expression. In summary, psychophysics, neuroimaging and neuropsychological methods all provide converging evidence for the independent processing of identity and expression within the face network. However, these same methods also supply converging evidence for a partial dependence of these two perceptual processes: in the expression aftereffect, the functional sensitivities of the FFA and pSTS, and identity deficits observed in a patient with primarily impaired expression perception and a spared inferotemporal cortex. Thus, future models of face perception must incorporate representations or regions which independently process identity or expression as well as those which are involved in the perception of both identity and expression.