No description available.

Face perception is impaired in a variety of ways in older adults, but the mechanisms underlying these changes remain unclear. A central theme of this dissertation is that task performance is constrained by two factors intrinsic to the observer: sources of random variability -- internal noise -- and the efficiency with which task-relevant stimulus information is utilized. This thesis uses several behavioural, psychophysical methods to examine how age-related changes in one or both of these factors affect face processing. Chapter 2 used the classification image (CI) method to characterize the spatial sampling patterns of younger and older observers performing a face discrimination task. Compared to younger adults, older adults used information in the eye/brow region less consistently and instead relied on relatively less informative regions such as the forehead. The differences in CIs accounted for the lower absolute efficiency that was found in older observers. Chapter 3 estimated internal noise and calculation efficiency by measuring threshold-vs.-noise (TvN) curves and response consistency in a face discrimination task. Compared to younger observers, older observers had higher additive internal noise and lower calculation efficiency, but the magnitude of multiplicative internal noise did not differ between age groups. Previous studies have shown that younger adults have a bias to rely on horizontal structure to discriminate and identify faces, and the magnitude of this so-called horizontal bias is correlated with identification accuracy. The experiments in Chapter 4 measured horizontal bias in younger and older adults, and found that age differences in horizontal bias account for some, but not all, of the age difference in face identification accuracy. In summary, my work demonstrates that additive (but not multiplicative) internal noise is greater in older adults, and that they are less efficient at sampling information that is conveyed by structure at different locations and orientations in a face. / Dissertation / Doctor of Science (PhD) / Our experience of the visual environment results from perceptual processes in the brain. Many of these processes change with age, such as our ability to identify someone from a photograph of their face. Performance is influenced by both random variability, or "noise", within the observer and how efficiently we use task-relevant information in the visual environment. By systematically manipulating the amount of available stimulus information I assessed the contribution of these factors to older adults' judgements of facial identity, and characterized the information on which these decisions are based. These experiments are the first to consider how face perception in older adults is constrained by the combined effects of internal noise and the efficiency with which the visual system utilizes various sources of information. The results provide a number of directions for future research in the fields of face perception and age-related changes in complex pattern vision.

No description available.

No description available.

Yes / Recent research has shown that adults with autism spectrum disorders (ASD) have difficulty interpreting others' emotional responses, in order to work out what actually happened to them. It is unclear what underlies this difficulty; important cues may be missed from fast paced dynamic stimuli, or spontaneous emotional responses may be too complex for those with ASD to successfully recognise. To explore these possibilities, 17 adolescents and adults with ASD and 17 neurotypical controls viewed 21 videos and pictures of peoples' emotional responses to gifts (chocolate, a handmade novelty or Monopoly money), then inferred what gift the person received and the emotion expressed by the person while eye movements were measured. Participants with ASD were significantly more accurate at distinguishing who received a chocolate or homemade gift from static (compared to dynamic) stimuli, but significantly less accurate when inferring who received Monopoly money from static (compared to dynamic) stimuli. Both groups made similar emotion attributions to each gift in both conditions (positive for chocolate, feigned positive for homemade and confused for Monopoly money). Participants with ASD only made marginally significantly fewer fixations to the eyes of the face, and face of the person than typical controls in both conditions. Results suggest adolescents and adults with ASD can distinguish subtle emotion cues for certain emotions (genuine from feigned positive) when given sufficient processing time, however, dynamic cues are informative for recognising emotion blends (e.g. smiling in confusion). This indicates difficulties processing complex emotion responses in ASD.

Yes / Humans manipulate objects chiefly within their lower visual field, a consequence of upright posture and the anatomical position of hands and arms.This study tested the hypothesis of enhanced sensitivity to a range of stimuli within the lower visual field. Following current models of hierarchical processing within the ventral steam, discrimination sensitivity was measured for orientation, curvature, shape (radial frequency patterns), and faces at various para-central locations (horizontal, vertical, and main diagonal meridians) and eccentricities (5° and 10°). Peripheral sensitivity was isotropic for orientation and curvature. By contrast, observers were significantly better at discriminating shapes throughout the lower visual field compared to elsewhere. For faces, however, peak sensitivity was found in the left visual field, corresponding to the right hemispheric localization of human face processing. Presenting head outlines without any internal features (e.g., eyes, mouth) recovered the lower visual field advantage found for simple shapes. A lower visual field preference for the shape of an object, which is absent for more localized information (orientation and curvature) but also for more complex objects (faces), is inconsistent with a strictly feed-forward model and poses a challenge for multistage models of object perception. The distinct lower visual field preference for contour shapes is, however, consistent with an asymmetry at intermediate stages of visual processing, which may play a key role in representing object characteristics that are particularly relevant to visually guided actions.

Dual-process models of recognition memory propose that recognition memory can be supported by either a general sense of familiarity or the recollection of the encoding context. One source of evidence supporting dual-process models comes from event-related potential (ERP) studies of recognition memory, which have identified distinct patterns of neural activity associated with familiarity and recollection (the mid frontal and left parietal old/new effects, respectively). In this thesis, dual-process accounts of recognition memory were investigated in a series of ERP studies using three categories of stimulus: previously unknown faces, famous faces, and names. For previously unknown faces, familiarity was associated with activity over posterior scalp electrodes while recollection was associated with topographically dissociable activity over anterior electrodes. These dissociable patterns of activity support dual-process models. However, the typical pattern of old/new effects was only observed for stimuli associated with pre-existing representations (i.e., names and famous faces), suggesting that the presence/absence of pre-existing representations may determine the particular retrieval processes that support recognition memory. Furthermore, recollection was associated with two different patterns of activity (anterior and left parietal effects), suggesting that recollection is not a homogenous process. Dual-process theories may represent an important starting point for investigating recognition memory, but neither familiarity nor recollection appear to be functionally homogenous processes when theorizing is constrained by the analysis of scalp recorded electrophysiological activity.

Le déficit social, incluant la perturbation du traitement du regard et des émotions, est au cœur de l’autisme. Des études ont montré que les visages de peur provoquent une orientation rapide et involontaire de l’attention spatiale vers leur emplacement chez les individus à développement typique. De plus, ceux-ci détectent plus rapidement et plus efficacement les visages avec un regard direct (vs regard dévié). La présente étude vise à explorer l’effet de l’émotion de peur et de la direction du regard (direct vs dévié) sur l’attention spatiale chez les enfants autistes à l’aide d’une tâche d’attention spatiale implicite. Six enfants avec un trouble autistique (TA) ont participé à cette étude. Les participants doivent détecter l’apparition d’une cible à gauche ou à droite d’un écran. L’apparition de la cible est précédée d’une amorce (paire de visages peur/neutre avec regard direct/dévié). La cible peut être présentée soit dans le même champ visuel que l’amorce émotionnellement chargée (condition valide), soit dans le champ visuel opposé (condition invalide). Nos résultats montrent que les amorces avec un visage de peur (vs les amorces avec un visage neutre) provoquent un effet d’interférence au niveau comportemental et divergent l’attention de leur emplacement chez les enfants avec un TA. / Autism is characterized by a social deficit, including difficulties in using and responding to facial expressions and gaze. Previous studies showed that fearful faces elicit a rapid involuntary orienting of spatial attention towards their location in typically developing (TD) individuals. In addition, target faces with direct gaze are detected faster and more efficiently than those with averted gaze in TD individuals. The aim of the current study is to explore the effect of fear and gaze direction (direct vs averted) on spatial attention in children with autistic disorder (AD). Six children with AD performed a covert spatial orienting task. Each trial consisted of a pair of faces (fearful/neutral with direct/averted gaze) briefly presented followed by a target presented at the location of one of the faces. Participants had to judge the location of the target (right or left visual field). The target unpredictably appeared on the side of the emotional face (fear, direct) (valid condition) or on the opposite side (neutral, averted) (invalid condition). Our results show that fearful faces have an interferent effect on the performance of AD children and divert attention from their location.

Dans ce travail, nous nous proposons d'étudier la cognition sociale chez les sourds en distinguant les aspects perceptifs et cognitifs selon le modèle proposé par Tager-Flusberg et Sullivan (2000). La surdité nous permet d'aborder l'influence des facteurs environnementaux sur le développement des composantes socio-perceptive et socio-cognitive ; nous ciblons nos recherches sur les enfants sourds nés de parents entendants, éduqués dans des écoles ordinaires et portants des prothèses auditives. La première question à laquelle nous tenterons de répondre est la suivante : le manque de communication avec l'entourage familial pendant les premiers mois de vie, en lien avec le contexte particulier de la surdité dans un milieu entendant, a-t-il une influence sur le développement de la composante socio-perceptive ? Nous étudions cette question avec deux expériences impliquant la perception des visages et des émotions ; ces tests nous permettent de mettre en évidence les performances et les stratégies de traitement utilisées. Nous recherchons d'une part, l'utilisation du processus configural et l'effet de focalisation de l'attention sur la région des yeux au cours d'une tâche de jugement de similarité entre visages et d'autre part, l'effet de traitement automatique de la colère avec une tâche de recherche visuelle. La deuxième question soulevée est relative au développement de la composante socio-cognitive, et notamment aux capacités liées à la théorie de l'esprit. Les possibilités croissantes d'intégration du discours, notamment grâce aux prothèses auditives, permettraient-elles le développement des capacités nécessaires à la compréhension des états mentaux d'autrui ? / In this thesis, we aimed to study the socio-perceptive and the socio-cognitive components of social cognition (Tager-Flusberg et Sullivan, 2000) in deaf children. Deafness give us the possibility to assess environmental factors' influence on the development of these components. To do so, we focus our studies on deaf children born from hearing parents, equipped with auditory protheses, and educated in ordinary schools. First, one of the main issue of the current studies is to assess whether the lack of communication with family during the first months of life, in line with the particular context of deafness in a hearing environment, have a significant impact on the socio-perceptive component. Experiments 1 and 2 were designed to assess this issue. Participants had to respond with two experiences related to faces and emotion perceptions ; those tests allow us to show the performances and the strategies of the treatment used. On a side, we are looking for the inversion effect and the eyes area focus effect during a test of faces' similarities judgment, and another side the angry automatic effect with a visual search test. The second question studied is related to the development of the socio-cognitive component, and especially on capacities of theory of mind. Could the improvement of internalization of speech, using auditory protheses, permit the development of the capacities needed to understand the state of mind of another? Or in contrary, are the possibilities to exchange precociously about his own state of mind needed to develop socio-cognitive component?

Abstract not available