A visibilidade da etapa fértil na mulher é uma questão polêmica e tem sido muito discutida nas últimas décadas. Alguns autores argumentam que no transcorrer da evolução a ovulação ficou oculta. Em paralelo, outros pesquisadores afirmam que a ovulação na mulher não se manifesta de forma tão visível como em alguns primatas que apresentam sinais muito notórios da ovulação, por exemplo, a tumefação vaginal. Mas diversas pesquisas têm fornecido evidência que mostram que o período fértil na mulher é perceptível de maneira sutil, sem que se tenha consciência do processo perceptual envolvido. Os achados destas pesquisas apontam para o fato de diversas características (como a face, a proporção cintura quadril, a simetria de tecidos brandos pareados e o cheiro) serem percebidas como mais atraentes na etapa fértil. O presente estudo teve por objetivo investigar se em alguma etapa (folicular tardia ou lútea) do ciclo menstrual a face da mulher se torna mais atraente para o sexo oposto devido a mudanças morfológicas induzidas pelos níveis hormonais. Foram apresentados, apenas para participantes masculinos, 36 slides com fotografias de faces frontais de mulheres em idade reprodutiva. Em cada slide foram mostradas simultaneamente duas fotos da mesma mulher, uma das fotos obtida na Fase Folicular Tardia (FFT) do ciclo e a outra obtida na Fase Lútea (FL). Os participantes escolheram a face mais atraente e posteriormente avaliaram o grau de atratividade mediante uma escala analógica visual (VAS), cujo extremo esquerdo e direito da escala foram rotulados respectivamente por: nem um pouco atraente e muito atraente. Os resultados mostraram que a atratividade facial feminina muda em função da etapa do ciclo menstrual. As faces das mulheres que não tomavam anticoncepcionais foram julgadas como mais atraentes na etapa fértil do que na etapa infértil do ciclo. E o julgamento de atratividade feito para as faces das mulheres que tomavam anticoncepcionais não diferiram significativamente entre a FFT e a FL. Os resultados obtidos nesta pesquisa e nos estudos realizados previamente proporcionam evidências que demonstram que o período fértil nos humanos não está oculto, pois ocorrem mudanças na face que são detectáveis, mesmo quando o processo de percepção não é ciente. / Visibility of fertile period in women is a controversial topic that has been broadly discussed during the last decades. Some authors argue that ovulation became hidden in the course of evolution. In contrast, some other researchers state that ovulation in woman is not manifested as visibly as in other primates, which present very evident signals of ovulation like, e.g., vaginal tumefaction. However, several studies have provided evidence showing that fertile period in women is perceptible in a subtle way, without being aware of the perceptual process involved. Findings of those works points to the fact that some characteristics such as face, waist hip ratio, paired soft tissues symmetry and smell are perceived as more attractive in the fertile stage. The present work aimed to find out whether in any stage (late follicular or luteal) of menstrual cycle woman face appears more attractive to opposite sex, due to morphological changes induced by hormonal levels. 36 slides with frontal face photographs of woman in reproductive age were shown to male participants. In each slide two pictures of the same woman, one obtained in the late follicular phase and the other obtained in the luteal phase were exposed. Participants chose the more attractive picture and then they assessed the attractiveness through a visual analogical scale (VAS), in whose left and right extremes the legends not attractive at all and very attractive were marked, respectively. Results showed that female facial attractiveness changes as a function of the menstrual cycle stage. Faces of women who did not take contraceptives did not differ significantly between FFT and FL. The results obtained in this research and previous studies provide evidence to demonstrate that the fertile period in humans is not hidden, because on the face occur changes that are detectable even when the process of perception is not aware of.

A técnica de campo visual dividido foi utilizada na análise dos padrões de assimetria cerebral para a percepção de expressões faciais de valência positiva e negativa. Oitenta universitários destros (65 mulheres, 15 homens) foram distribuídos em cinco grupos experimentais com o objetivo de se investigar separadamente a percepção de expressões de alegria, medo, surpresa, tristeza e da face neutra. Em cada apresentação de estímulo, uma face alvo e uma face distratora eram apresentadas à direita ou à esquerda de um ponto de fixação localizado no centro da tela do computador. O tempo de apresentação dos estímulos foi de 150 ms e os participantes tiveram que determinar o lado (esquerdo ou direito) em que havia sido apresentada a face alvo, utilizando um mouse para responderem aos estímulos. As análises estatísticas de tempo de reação e erros de julgamento indicaram não haver diferenças entre o desempenho de homens e mulheres na tarefa experimental. Expressões faciais de alegria e medo foram identificadas mais rapidamente quando apresentadas no campo visual esquerdo, indicando uma possível vantagem do hemisfério direito na percepção destas emoções. Menores tempos de reação e erros de julgamento foram observados para as condições de pareamento em que faces emocionais foram apresentadas no campo visual esquerdo e faces neutras no campo visual direito. A análise dos pareamentos entre faces indicou que faces neutras e de alegria são percebidas mais rapidamente e com maior acerto que faces de medo e tristeza. Embora não tenha havido uma vantagem do hemisfério direito para a percepção de todas as expressões faciais, os resultados deste estudo tendem a concordar com a hipótese do hemisfério direito para o processamento emocional. / The divided visual field technique was used to analize the patterns of brain asymmetry in the perception of positive and negative facial expressions. Eighty undergraduate students (65 female, 15 male) were distributed in five experimental groups in order to investigate separately the perception of expressions of happiness, surprise, fear, sadness, and neutral. In each trial, a target and a distractor expression were presented in a computer screen during 150 ms and participants had to determine the side (left or right) on which the target expression was presented using a mouse to respond to the stimuli. Time reaction and judgment errors analysis showed no differences between men and womens performance in experimental task. Results indicated that expressions of happiness and fear were identified faster when presented on the left visual field, suggesting an advantage of the right hemisphere in the perception of these expressions. Fewer judgment errors and faster reaction times were observed for the matching condition in which emotional faces were presented on the left visual field and neutral faces on the right visual field. Analysis of the pairs of faces indicated that neutral and happy faces were perceived faster and more accurately than faces of fear and happiness. Although an advantage of the right hemisphere was not occurred for the perception of all expressions, results tend to support the right hemisphere hypothesis for emotional processing.

A visibilidade da etapa fértil na mulher é uma questão polêmica e tem sido muito discutida nas últimas décadas. Alguns autores argumentam que no transcorrer da evolução a ovulação ficou oculta. Em paralelo, outros pesquisadores afirmam que a ovulação na mulher não se manifesta de forma tão visível como em alguns primatas que apresentam sinais muito notórios da ovulação, por exemplo, a tumefação vaginal. Mas diversas pesquisas têm fornecido evidência que mostram que o período fértil na mulher é perceptível de maneira sutil, sem que se tenha consciência do processo perceptual envolvido. Os achados destas pesquisas apontam para o fato de diversas características (como a face, a proporção cintura quadril, a simetria de tecidos brandos pareados e o cheiro) serem percebidas como mais atraentes na etapa fértil. O presente estudo teve por objetivo investigar se em alguma etapa (folicular tardia ou lútea) do ciclo menstrual a face da mulher se torna mais atraente para o sexo oposto devido a mudanças morfológicas induzidas pelos níveis hormonais. Foram apresentados, apenas para participantes masculinos, 36 slides com fotografias de faces frontais de mulheres em idade reprodutiva. Em cada slide foram mostradas simultaneamente duas fotos da mesma mulher, uma das fotos obtida na Fase Folicular Tardia (FFT) do ciclo e a outra obtida na Fase Lútea (FL). Os participantes escolheram a face mais atraente e posteriormente avaliaram o grau de atratividade mediante uma escala analógica visual (VAS), cujo extremo esquerdo e direito da escala foram rotulados respectivamente por: nem um pouco atraente e muito atraente. Os resultados mostraram que a atratividade facial feminina muda em função da etapa do ciclo menstrual. As faces das mulheres que não tomavam anticoncepcionais foram julgadas como mais atraentes na etapa fértil do que na etapa infértil do ciclo. E o julgamento de atratividade feito para as faces das mulheres que tomavam anticoncepcionais não diferiram significativamente entre a FFT e a FL. Os resultados obtidos nesta pesquisa e nos estudos realizados previamente proporcionam evidências que demonstram que o período fértil nos humanos não está oculto, pois ocorrem mudanças na face que são detectáveis, mesmo quando o processo de percepção não é ciente. / Visibility of fertile period in women is a controversial topic that has been broadly discussed during the last decades. Some authors argue that ovulation became hidden in the course of evolution. In contrast, some other researchers state that ovulation in woman is not manifested as visibly as in other primates, which present very evident signals of ovulation like, e.g., vaginal tumefaction. However, several studies have provided evidence showing that fertile period in women is perceptible in a subtle way, without being aware of the perceptual process involved. Findings of those works points to the fact that some characteristics such as face, waist hip ratio, paired soft tissues symmetry and smell are perceived as more attractive in the fertile stage. The present work aimed to find out whether in any stage (late follicular or luteal) of menstrual cycle woman face appears more attractive to opposite sex, due to morphological changes induced by hormonal levels. 36 slides with frontal face photographs of woman in reproductive age were shown to male participants. In each slide two pictures of the same woman, one obtained in the late follicular phase and the other obtained in the luteal phase were exposed. Participants chose the more attractive picture and then they assessed the attractiveness through a visual analogical scale (VAS), in whose left and right extremes the legends not attractive at all and very attractive were marked, respectively. Results showed that female facial attractiveness changes as a function of the menstrual cycle stage. Faces of women who did not take contraceptives did not differ significantly between FFT and FL. The results obtained in this research and previous studies provide evidence to demonstrate that the fertile period in humans is not hidden, because on the face occur changes that are detectable even when the process of perception is not aware of.

Desde a segunda metade do século XX, pesquisadores relatam que bebês olham preferencialmente para faces humanas em comparação a outros estímulos visuais. Estudos sugerem que essa preferência já pode ser encontrada nos recém-nascidos, indicando a possibilidade de algum mecanismo inato de direcionamento do olhar para os co-específicos, ou seja, para outros indivíduos pertencentes à mesma espécie. Porém, as teorias construídas para explicar esse fenômeno propuseram modelos que não se aplicam exclusivamente ao ser humano, como o padrão CONSPEC (Morton & Johnson, 1991), no qual três pontos de contraste (correspondentes aos olhos e à boca) seriam o elemento atrativo das faces humanas. Contudo, esse padrão não é exclusivo da face humana, mas também está presente nas faces de outros animais. Em estudo anterior (Faria, 2009), comparando faces bidimensionais de diferentes espécies, não se verificou preferência pela face humana. Nesse contexto, o objetivo desta pesquisa é aprofundar o estudo da preferência visual de faces pelos recém-nascidos por meio da utilização de estímulos tridimensionais de diferentes espécies, bem como verificar a capacidade dos recém-nascidos em imitar movimentos de objetos inanimados, mas correspondentes a movimentos humanos. Foram realizados três experimentos, com o total de 77 bebês em suas primeiras horas após o parto. Os resultados sugerem que o padrão CONSPEC não é o único fator de atração visual para os recém-nascidos e que eles são capazes de imitar movimentos que julgam semelhantes aos humanos, ainda que realizados por fantoches. Os mecanismos de preferência dos recém-nascidos para faces não seriam, portanto, específicos para a espécie humana, mas são suficientes para assegurar um início bem sucedido de construção da cognição social / Since the second half of the twentieth century, researchers have reported that one of the most visually preferred stimuli by infants is the human face. Several studies suggest that this preference is already found in newborns, indicating the possibility of some innate mechanism that might direct the gaze of newborns to co-specifics (other individuals belonging to the same species). However, theories to explain this phenomenon have proposed models that do not apply exclusively to humans as the CONSPEC (Morton and Johnson, 1991), which states that a three-dot pattern (corresponding to eyes and mouth) would be the attractive features of human faces. Nevertheless, this pattern is not unique to the human face, but is also present in other animal faces. Previous study (Faria, 2009) compared two-dimensional faces of different species, finding out there was no specific preference for the human face. In this context, the objective of this research is to improve the study of the newborns visual preference for faces, using three-dimensional stimuli of different species, and to verify if newborns could imitate movements performed by inanimate objects, but correspondent to human movements. There were performed three experiments with 77 infants in their first hours after birth. The results suggest that CONSPEC pattern is not the only factor to elicit newborns visual preference and that they are able to imitate human-like movements, even if performed by puppets. The mechanisms for tracking faces are not specifically aimed to the human species, but are sufficient to ensure the beginning of a successful construction of social cognition

Thomas Kin Fong Lei. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 64-66). / Abstracts in English and Chinese. / LIST OF FIGURES --- p.IV / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Model-based Control of SMA Wires --- p.3 / Chapter 2.1 --- Model Identification of SMA Wires --- p.3 / Chapter 2.1.1 --- Temperature-Current Relationship --- p.3 / Chapter 2.1.2 --- Stress-Strain Relationship --- p.5 / Chapter 2.1.3 --- Martensite Fraction-Temperature Relationship --- p.8 / Chapter 2.2 --- Model-based Position Control of Two Linking SMA Wires --- p.9 / Chapter 2.3 --- Summary --- p.12 / Chapter 3 --- Neural-fuzzy-based Control of SMA Wires --- p.13 / Chapter 3.1 --- Adaptive Neuro-fuzzy Inference System (ANFIS) --- p.13 / Chapter 3.1.1 --- ANFIS Architecture --- p.13 / Chapter 3.1.2 --- Hybrid Learning Algorithm --- p.16 / Chapter 3.2 --- Generalized Neural Network (GNN) --- p.20 / Chapter 3.2.1 --- GNN Architecture --- p.20 / Chapter 3.2.2 --- Approximation of the GNN --- p.22 / Chapter 3.2.3 --- Backpropagation Training Algorithm --- p.24 / Chapter 3.2.4 --- Complexity Reduction of the GNN --- p.25 / Chapter 3.2.5 --- Error Bound of In-exact Reduction of the GNN --- p.29 / Chapter 3.3 --- Neural-fuzzy-based Position Control of Four Linking SMA Wires --- p.32 / Chapter 3.3.1 --- ANFIS-based Position Control of Four Linking SMA Wires --- p.32 / Chapter 3.3.2 --- GNN-based Position Control of Four Linking SMA Wires --- p.35 / Chapter 3.3.3 --- Performance Comparison of ANFIS and GNN Algorithms --- p.37 / Chapter 3.4 --- Summary --- p.39 / Chapter 4 --- SMA Actuated Artificial Face --- p.40 / Chapter 4.1 --- Muscles of the Human Face --- p.40 / Chapter 4.2 --- The Software Part: facial model --- p.41 / Chapter 4.3 --- The Hardware Part: artificial face and peripheral interface --- p.43 / Chapter 4.3.1 --- SMA Actuated Artificial Face --- p.43 / Chapter 4.3.2 --- Peripheral Interface --- p.45 / Chapter 4.4 --- Position Control on the Artificial Face --- p.47 / Chapter 4.4.1 --- Model-based Position Control on Artificial Face --- p.48 / Chapter 4.4.2 --- Neural-fuzzy-based Position Control on Artificial Face --- p.49 / Chapter 4.4.3 --- Comparison of the Model-based and Reduced GNN Control of Artificial Face --- p.49 / Chapter 4.5 --- Experimental Result --- p.50 / Chapter 5 --- Conclusion --- p.52 / Appendix1 --- p.53 / Appendix2 --- p.55 / Appendix3 --- p.56 / Appendix4 --- p.58 / Bibliography --- p.64

A long standing debate in psychological science is whether the face signals specific emotions. Basic emotion theory presupposes that there are coordinated facial musculature movements that individuals can identify as relating to a core set of basic emotions. In opposition to this view, the constructionist theory contends that the perception of emotion is a far more intricate process involving semantic knowledge and arousal states. The aim of the current investigation was to explore some of the questions at the crux of this debate. We showed participants video clips of real people in real time, where the face was in motion, much as in everyday life. In study 1 we directly manipulated the effects of context to determine what influences emotion perception – situational information or the face? In support of the basic emotion view, participants identified displays of happiness, anger and sadness irrespective of contextual information provided. Importantly, participants also rated one set of facial movements as more intensely expressing a ‘sad’ face. Study 1 also demonstrated unique context effects in partial support for the constructionist view, suggesting that for some facial expressions, the role of context may be important. In study 2, we explored the possible effects that language has on the perception of emotion. In the absence of linguistic cues, participants used significantly more ‘happy’ and ‘sad’ words to label the basic emotion prototype for happiness and for the ‘sad’ face introduced in study 1. Overall, findings from these studies suggest that although contextual cues may be important for specific scenarios, the face is dominant to the layperson when inferring the emotional state of another.

Tang Yuk Ming = 電影中三維人面模型之估計 / 鄧育明. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 107-113). / Text in English; abstracts in English and Chinese. / Tang Yuk Ming = Dian ying zhong san wei ren mian mo xing zhi gu ji / Deng Yuming. / Acknowledgement --- p.i / Abstract --- p.ii / Contents --- p.vi / List of Figures --- p.viii / List of Tables --- p.x / List of Abbreviations and Notations --- p.xi / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Recent Research Works --- p.2 / Chapter 1.2.1 --- Face modeling from images --- p.2 / Chapter 1.2.2 --- Pose estimation --- p.4 / Chapter 1.3 --- Objectives and Assumptions --- p.7 / Chapter 1.4 --- Our Method --- p.8 / Chapter 1.5 --- Thesis Outline --- p.10 / Chapter 2. --- Basic Theory on 3D Modeling of a Head --- p.11 / Chapter 2.1 --- Introduction --- p.11 / Chapter 2.2 --- Perspective Projection --- p.13 / Chapter 2.3 --- Initialization --- p.17 / Chapter 2.3.1 --- Generic wireframe face model and fiducial points --- p.17 / Chapter 2.3.2 --- Deformations --- p.22 / Chapter 2.3.3 --- Experimental results --- p.35 / Chapter 2.4 --- Summary --- p.39 / Chapter 3. --- Pose Estimation --- p.40 / Chapter 3.1 --- Introduction --- p.40 / Chapter 3.2 --- Problem Description --- p.42 / Chapter 3.3 --- Iterative Least-Square Minimization --- p.45 / Chapter 3.3.1 --- Depth estimation --- p.45 / Chapter 3.3.2 --- Least-square minimization --- p.47 / Chapter 3.3.3 --- Iterative process --- p.52 / Chapter 3.4 --- Experimental Results --- p.54 / Chapter 3.4.1 --- Synthetic data --- p.54 / Chapter 3.4.2 --- Real data --- p.65 / Chapter 3.5 --- Summary --- p.69 / Chapter 4. --- 3D Wireframe Model Estimation --- p.70 / Chapter 4.1 --- Introduction --- p.70 / Chapter 4.2 --- 3D Wireframe Model Estimation --- p.72 / Chapter 4.2.1 --- Least-square minimization --- p.73 / Chapter 4.2.2 --- Iterative process --- p.74 / Chapter 4.3 --- 3D Wireframe Model Estimation of the Subsequent Frames --- p.77 / Chapter 4.4 --- Experimental Results --- p.78 / Chapter 4.4.1 --- Synthetic data --- p.78 / Chapter 4.4.2 --- Real data --- p.84 / Chapter 4.5 --- Summary --- p.98 / Chapter 5. --- Contributions and Conclusions --- p.99 / Chapter 5.1 --- Contributions and conclusions --- p.99 / Chapter 5.2 --- Future Developments --- p.102 / Appendix A Triangles and vertices on the IST model --- p.104 / Bibliography --- p.107

Background Individuals with Autism Spectrum Disorder (ASD) have been reported to show socio-communicative impairments which are associated with impaired face perception and atypical gaze behaviour. Attending to faces and interpreting the important socio-communicative cues presented allows us to understand other’s cognitive states, emotions, wants and desires. This information enables successful social encounters and interactions to take place. Children with ASD not attending to these important social cues on the face may cause some of the socio-communicative impairments observed within this population. Examining how children with ASD attend to faces will enhance our understanding of their communicative impairments. Aim The present thesis therefore aimed to use eye-tracking methodology to examine attention allocation to faces for communicative cues in children with ASD. Method The first line of enquiry examined how children with ASD (n = 21; age = 13y7m) attended to faces presented within their picture communication systems compared to typically developing children matched on chronological age, verbal ability age and visuo-spatial ability age. The next investigation was conducted on the same group of children and examined how children with ASD attended to faces of different familiarity including, familiar, unfamiliar and the child’s own face. These faces were also presented with direct gaze or averted gaze to investigate how this would impact on the children’s allocation of attention. The final exploration highlighted how children with ASD (n = 20; age = 12y3m) attended to socially salient information (faces) and non-socially salient information (objects) presented within social scenes of varying complexity, compared to typically developing controls. Again groups were matched based on chronological age, verbal ability age, and visuo-spatial ability age. Results Children with ASD were shown to allocate attention to faces presented within their picture communication symbols similarly compared to their typically developing counterparts. All children were shown to fixate significantly longer on the face images compared to the object images. The children with ASD fixated for similar amounts of time to the eye and mouth regions regardless of familiarity and gaze direction compared to their controlled matches. All groups looked significantly longer at the eye areas compared to the mouth areas of the faces across all familiarity types. The children also fixated longer on the eye and mouth regions of direct gazing faces compared to the regions presented on the averted gazing faces. The children with ASD fixated on the faces and objects presented within social scenes similar to their typically developing counterparts across all complexity conditions. The children were shown to fixate significantly longer on the objects compared to the faces. Conclusions Children with ASD showed typical allocation of attention to faces. This suggests that faces are not aversive to them and they are able to attend to the relevant areas such as eye and mouth regions. This may have been influenced by the inclusion of high functioning children with ASD. However these results may also suggest that attention allocation and gaze behaviour are not the only factors which contribute to the socio-communicative impairments observed in ASD.

Eyewitness recognition is acknowledged to be prone to error but there is less understanding of difficulty in discriminating unfamiliar faces. This thesis examined the effects of face perception on identification of facial composites, and on unfamiliar face image comparison. Facial composites depict face memories by reconstructing features and configurations to form a likeness. They are generally reconstructed from an unfamiliar face memory, and will be unavoidably flawed. Identification will require perception of any accurate features, by someone who is familiar with the suspect and performance is typically poor. In typical face perception, face images are processed efficiently as complete units of information. Chapter 2 explored the possibility that holistic processing of inaccurate composite configurations will impair identification of individual features. Composites were split below the eyes and misaligned to impair holistic analysis (cf. Young, Hellawell, & Jay, 1987); identification was significantly enhanced, indicating that perceptual expertise with inaccurate configurations exerts powerful effects that can be reduced by enabling featural analysis. Facial composite recognition is difficult, which means that perception and judgement will be influence by an affective recognition bias: smiles enhance perceived familiarity, while negative expressions produce the opposite effect. In applied use, facial composites are generally produced from unpleasant memories and will convey negative expression; affective bias will, therefore, be important for facial composite recognition. Chapter 3 explored the effect of positive expression on composite identification: composite expressions were enhanced, and positive affect significantly increased identification. Affective quality rather than expression strength mediated the effect, with subtle manipulations being very effective. Facial image comparison (FIC) involves discrimination of two or more face images. Accuracy in unfamiliar face matching is typically in the region of 70%, and as discrimination is difficult, may be influenced by affective bias. Chapter 4 explored the smiling face effect in unfamiliar face matching. When multiple items were compared, positive affect did not enhance performance and false positive identification increased. With a delayed matching procedure, identification was not enhanced but in contrast to face recognition and simultaneous matching, positive affect improved rejection of foil images. Distinctive faces are easier to discriminate. Chapter 5 evaluated a systematic caricature transformation as a means to increase distinctiveness and enhance discrimination of unfamiliar faces. Identification of matching face images did not improve, but successful rejection of non-matching items was significantly enhanced. Chapter 6 used face matching to explore the basis of own race bias in face perception. Other race faces were manipulated to show own race facial variation, and own race faces to show African American facial variation. When multiple face images were matched simultaneously, the transformation impaired performance for all of the images; but when images were individually matched, the transformation improved perception of other race faces and discrimination of own race faces declined. Transformation of Japanese faces to show own race dimensions produced the same pattern of effects but failed to reach significance. The results provide support for both perceptual expertise and featural processing theories of own race bias. Results are interpreted with reference to face perception theories; implications for application and future study are discussed.

Les stimuli naturels projetés sur nos rétines nous fournissent de l’information visuelle riche. Cette information varie le long de propriétés de « bas niveau » telles que la luminance, le contraste, et les fréquences spatiales. Alors qu’une partie de cette information atteint notre conscience, une autre partie est traitée dans le cerveau sans que nous en soyons conscients. Les propriétés de l’information influençant l’activité cérébrale et le comportement de manière consciente versus non-consciente demeurent toutefois peu connues. Cette question a été examinée dans les deux derniers articles de la présente thèse, en exploitant les techniques psychophysiques développées dans les deux premiers articles. Le premier article présente la boîte à outils SHINE (spectrum, histogram, and intensity normalization and equalization), développée afin de permettre le contrôle des propriétés de bas niveau de l'image dans MATLAB. Le deuxième article décrit et valide la technique dite des bulles fréquentielles, qui a été utilisée tout au long des études de cette thèse pour révéler les fréquences spatiales utilisées dans diverses tâches de perception des visages. Cette technique offre les avantages d’une haute résolution au niveau des fréquences spatiales ainsi que d’un faible biais expérimental. Le troisième et le quatrième article portent sur le traitement des fréquences spatiales en fonction de la conscience. Dans le premier cas, la méthode des bulles fréquentielles a été utilisée avec l'amorçage par répétition masquée dans le but d’identifier les fréquences spatiales corrélées avec les réponses comportementales des observateurs lors de la perception du genre de visages présentés de façon consciente versus non-consciente. Les résultats montrent que les mêmes fréquences spatiales influencent de façon significative les temps de réponse dans les deux conditions de conscience, mais dans des sens opposés. Dans le dernier article, la méthode des bulles fréquentielles a été combinée à des enregistrements intracrâniens et au Continuous Flash Suppression (Tsuchiya & Koch, 2005), dans le but de cartographier les fréquences spatiales qui modulent l'activation de structures spécifiques du cerveau (l'insula et l'amygdale) lors de la perception consciente versus non-consciente des expressions faciales émotionnelles. Dans les deux régions, les résultats montrent que la perception non-consciente s'effectue plus rapidement et s’appuie davantage sur les basses fréquences spatiales que la perception consciente. La contribution de cette thèse est donc double. D’une part, des contributions méthodologiques à la recherche en perception visuelle sont apportées par l'introduction de la boîte à outils SHINE ainsi que de la technique des bulles fréquentielles. D’autre part, des indications sur les « corrélats de la conscience » sont fournies à l’aide de deux approches différentes. / Natural stimuli impinging on our retinas provide us with a wealth of visual information. This information varies along “low-level” features, such as luminance, contrast, and spatial frequency (SF). Whereas some of this information reaches our awareness, some of it is processed in the brain without us ever becoming aware of it (i.e., non-consciously). A remaining question is precisely which SFs influence brain activation and behavior consciously vs. non-consciously. The aim of this thesis was to address this question using state-of the-art psychophysical techniques. The first article introduces the SHINE (spectrum, histogram, and intensity normalization and equalization) toolbox for controlling low-level image properties in MATLAB. The second article describes and validates the SF Bubbles technique, which was used throughout the studies in this thesis to map SF tuning for various face perception tasks with a high SF resolution and low experimental bias. The third and fourth articles focus on SF processing as a function of awareness. In the former, SF Bubbles was employed together with repetition priming and masking to investigate which SFs are correlated with observers’ behavioral responses during conscious vs. non-conscious face-gender perception. The results show that the same SFs significantly influenced response times in both prime awareness conditions but, surprisingly, in opposite ways. In the latter, SF Bubbles was combined with intracranial recordings from awake human patients and Continuous Flash Suppression (Tsuchiya & Koch, 2005). This allowed us to map the SFs that modulate activation in specific brain structures (the insula and the amygdala) during the conscious vs. non-conscious perception of emotional facial expressions. The results for both regions demonstrate that non-conscious perception relied on low SFs more and was faster than conscious perception. The contribution made in this thesis is thus two-fold: methodological contributions to visual perception research are made by introducing the SHINE toolbox and the SF Bubbles technique, and insights into the “informational correlates” of consciousness are provided from two different angles.