Eye movements are functional during face learning

Local Jekyll and global Hyde: the dual identity of face identification

The main concern in face-processing research is to understand the processes underlying the identification of faces. In the study reported here, we addressed this issue by examining whether local or global information supports face identification. We developed a new methodology called "iHybrid." This technique combines two famous identities in a gaze-contingent paradigm, which simultaneously provides local, foveated information from one face and global, complementary information from a second face. Behavioral face-identification performance and eye-tracking data showed that the visual system identified faces on the basis of either local or global information depending on the location of the observer's first fixation. In some cases, a given observer even identified the same face using local information on one trial and global information on another trial. A validation in natural viewing conditions confirmed our findings. These results clearly demonstrate that face identification is not rooted in a single, or even preferred, information-gathering strategy.

Gaze patterns during identity and emotion judgments in hearing adults and deaf users of American Sign Language

Deaf individuals rely on facial expressions for emotional, social, and linguistic cues. In order to test the hypothesis that specialized experience with faces can alter typically observed gaze patterns, twelve hearing adults and twelve deaf, early-users of American Sign Language judged the emotion and identity of expressive faces (including whole faces, and isolated top and bottom halves), while accuracy and fixations were recorded. Both groups recognized individuals more accurately from top than bottom halves, and emotional expressions from bottom than top halves. Hearing adults directed the majority of fixations to the top halves of faces in both tasks, but fixated the bottom half slightly more often when judging emotion than identity. In contrast, deaf adults often split fixations evenly between the top and bottom halves regardless of task demands. These results suggest that deaf adults have habitual fixation patterns that may maximize their ability to gather information from expressive faces.

Recognition Memory Strength is Predicted by Pupillary Responses at Encoding While Fixation Patterns Distinguish Recollection from Familiarity

Thirty-five healthy participants incidentally encoded a set of man-made and natural object pictures, while their pupil response and eye movements were recorded. At retrieval, studied and new stimuli were rated as novel, familiar (strong, moderate, or weak), or recollected. We found that both pupil response and fixation patterns at encoding predict later recognition memory strength. The extent of pupillary response accompanying incidental encoding was found to be predictive of subsequent memory. In addition, the number of fixations was also predictive of later recognition memory strength, suggesting that the accumulation of greater visual detail, even for single objects, is critical for the creation of a strong memory. Moreover, fixation patterns at encoding distinguished between recollection and familiarity at retrieval, with more dispersed fixations predicting familiarity and more clustered fixations predicting recollection. These data reveal close links between the autonomic control of pupil responses and eye movement patterns on the one hand and memory encoding on the other. Moreover, the data illustrate quantitative as well as qualitative differences in the incidental visual processing of stimuli, which are differentially predictive of the strength and the kind of memory experienced at recognition.

Comparing social attention in autism and amygdala lesions: effects of stimulus and task condition

The amygdala plays a critical role in orienting gaze and attention to socially salient stimuli. Previous work has demonstrated that SM a patient with rare bilateral amygdala lesions, fails to fixate and make use of information from the eyes in faces. Amygdala dysfunction has also been implicated as a contributing factor in autism spectrum disorders (ASD), consistent with some reports of reduced eye fixations in ASD. Yet, detailed comparisons between ASD and patients with amygdala lesions have not been undertaken. Here we carried out such a comparison, using eye tracking to complex social scenes that contained faces. We presented participants with three task conditions. In the Neutral task, participants had to determine what kind of room the scene took place in. In the Describe task, participants described the scene. In the Social Attention task, participants inferred where people in the scene were directing their attention. SM spent less time looking at the eyes and much more time looking at the mouths than control subjects, consistent with earlier findings. There was also a trend for the ASD group to spend less time on the eyes, although this depended on the particular image and task. Whereas controls and SM looked more at the eyes when the task required social attention, the ASD group did not. This pattern of impairments suggests that SM looks less at the eyes because of a failure in stimulus-driven attention to social features, whereas individuals with ASD look less at the eyes because they are generally insensitive to socially relevant information and fail to modulate attention as a function of task demands. We conclude that the source of the social attention impairment in ASD may arise upstream from the amygdala, rather than in the amygdala itself.

Does temporal integration of face parts reflect holistic processing?

We examined whether temporal integration of face parts reflects holistic processing or response interference. Participants learned to name two faces "Fred" and two "Bob." At test, the top and bottom halves of different faces formed composites and were presented briefly separated in time. Replicating prior findings (Singer & Sheinberg, Vision Research, 46, 1838-1847, 2006), naming of the target half for aligned composites was slowed when the irrelevant half was from a face with a different name rather than from the original face. However, no interference was observed when the irrelevant half had a name identical to the name of the target half but came from a different learned face, arguing against a true holistic effect. Instead, response interference was obtained when the target half briefly preceded the irrelevant half. Experiment 2 confirmed a double dissociation of holistic processing versus response interference for intact faces versus temporally separated face halves, suggesting that simultaneous presentation of facial information is critical for holistic processing.

Exploring the time course of face matching: temporal constraints impair unfamiliar face identification under temporally unconstrained viewing

The identification of unfamiliar faces has been studied extensively with matching tasks, in which observers decide if pairs of photographs depict the same person (identity matches) or different people (mismatches). In experimental studies in this field, performance is usually self-paced under the assumption that this will encourage best-possible accuracy. Here, we examined the temporal characteristics of this task by limiting display times and tracking observers' eye movements. Observers were required to make match/mismatch decisions to pairs of faces shown for 200, 500, 1000, or 2000ms, or for an unlimited duration. Peak accuracy was reached within 2000ms and two fixations to each face. However, intermixing exposure conditions produced a context effect that generally reduced accuracy on identity mismatch trials, even when unlimited viewing of faces was possible. These findings indicate that less than 2s are required for face matching when exposure times are variable, but temporal constraints should be avoided altogether if accuracy is truly paramount. The implications of these findings are discussed.

Developing cultural differences in face processing

Perception and eye movements are affected by culture. Adults from Eastern societies (e.g. China) display a disposition to process information holistically, whereas individuals from Western societies (e.g. Britain) process information analytically. Recently, this pattern of cultural differences has been extended to face processing. Adults from Eastern cultures fixate centrally towards the nose when learning and recognizing faces, whereas adults from Western societies spread fixations across the eye and mouth regions. Although light has been shed on how adults can fixate different areas yet achieve comparable recognition accuracy, the reason why such divergent strategies exist is less certain. Although some argue that culture shapes strategies across development, little direct evidence exists to support this claim. Additionally, it has long been claimed that face recognition in early childhood is largely reliant upon external rather than internal face features, yet recent studies have challenged this theory. To address these issues, we tested children aged 7-12 years of age from the UK and China with an old/new face recognition paradigm while simultaneously recording their eye movements. Both populations displayed patterns of fixations that were consistent with adults from their respective cultural groups, which 'strengthened' across development as qualified by a pattern classifier analysis. Altogether, these observations suggest that cultural forces may indeed be responsible for shaping eye movements from early childhood. Furthermore, fixations made by both cultural groups almost exclusively landed on internal face regions, suggesting that these features, and not external features, are universally used to achieve face recognition in childhood.

Social experience does not abolish cultural diversity in eye movements

Adults from Eastern (e.g., China) and Western (e.g., USA) cultural groups display pronounced differences in a range of visual processing tasks. For example, the eye movement strategies used for information extraction during a variety of face processing tasks (e.g., identification and facial expressions of emotion categorization) differs across cultural groups. Currently, many of the differences reported in previous studies have asserted that culture itself is responsible for shaping the way we process visual information, yet this has never been directly investigated. In the current study, we assessed the relative contribution of genetic and cultural factors by testing face processing in a population of British Born Chinese adults using face recognition and expression classification tasks. Contrary to predictions made by the cultural differences framework, the majority of British Born Chinese adults deployed "Eastern" eye movement strategies, while approximately 25% of participants displayed "Western" strategies. Furthermore, the cultural eye movement strategies used by individuals were consistent across recognition and expression tasks. These findings suggest that "culture" alone cannot straightforwardly account for diversity in eye movement patterns. Instead a more complex understanding of how the environment and individual experiences can influence the mechanisms that govern visual processing is required.

Can changes in eye movement scanning alter the age-related deficit in recognition memory?

Older adults typically exhibit poorer face recognition compared to younger adults. These recognition differences may be due to underlying age-related changes in eye movement scanning. We examined whether older adults' recognition could be improved by yoking their eye movements to those of younger adults. Participants studied younger and older faces, under free viewing conditions (bases), through a gaze-contingent moving window (own), or a moving window which replayed the eye movements of a base participant (yoked). During the recognition test, participants freely viewed the faces with no viewing restrictions. Own-age recognition biases were observed for older adults in all viewing conditions, suggesting that this effect occurs independently of scanning. Participants in the bases condition had the highest recognition accuracy, and participants in the yoked condition were more accurate than participants in the own condition. Among yoked participants, recognition did not depend on age of the base participant. These results suggest that successful encoding for all participants requires the bottom-up contribution of peripheral information, regardless of the locus of control of the viewer. Although altering the pattern of eye movements did not increase recognition, the amount of sampling of the face during encoding predicted subsequent recognition accuracy for all participants. Increased sampling may confer some advantages for subsequent recognition, particularly for people who have declining memory abilities.

Individual differences in face memory and eye fixation patterns during face learning

This study examined the relationship between individual differences in face memory and eye fixation patterns during face learning. Participants watched short movies of 20 faces and were divided into high and low face memory groups based on their performance in a recognition memory test. No qualitative difference was observed in the eye fixation distribution between high and low groups. Both groups mostly fixed on the internal region of faces, especially the eyes. A difference in the eye fixation pattern by groups was observed in the number of fixations and total fixation time on the eyes, which reflected high face memory participants moving their eyes between the left and right eyes more frequently than low face memory participants. These findings suggest that fixation on the eyes has a functional role in face memory and is related to individual differences in face memory.

Holistic face processing in newborns, 3-month-old infants, and adults: evidence from the composite face effect

Holistic face processing was investigated in newborns, 3-month-old infants, and adults through a modified version of the composite face paradigm and the recording of eye movements. After familiarization to the top portion of a face, participants (N = 70) were shown 2 aligned or misaligned faces, 1 of which comprised the familiar top part. In the aligned condition, no visual preference was found at any group age. In the misaligned condition, 3-month-olds preferred the face stimulus with the familiar top part, adults preferred the face stimulus with the novel one, and newborns did not manifest any visual preference. Results revealed that both infants' and adults' eye movements may be affected by holistic face information and demonstrated holistic face processing in 3-month-olds.

Inverting faces does not abolish cultural diversity in eye movements

Face processing is widely understood to be a basic, universal visual function effortlessly achieved by people from all cultures and races. The remarkable recognition performance for faces is markedly and specifically affected by picture-plane inversion: the so-called face-inversion effect (FIE), a finding often used as evidence for face-specific mechanisms. However, it has recently been shown that culture shapes the way people deploy eye movements to extract information from faces. Interestingly, the comparable lack of experience with inverted faces across cultures offers a unique opportunity to establish the extent to which such cultural perceptual biases in eye movements are robust, but also to assess whether face-specific mechanisms are universally tuned. Here we monitored the eye movements of Western Caucasian (WC) and East Asian (EA) observers while they learned and recognised WC and EA inverted faces. Both groups of observers showed a comparable impairment in recognising inverted faces of both races. WC observers deployed a scattered inverted triangular scanpath with a bias towards the mouth, whereas EA observers uniformly extended the focus of their fixations from the centre towards the eyes. Overall, our data show that cultural perceptual differences in eye movements persist during the FIE, questioning the universality of face-processing mechanisms.

Potential social interactions are important to social attention

Social attention, or how spatial attention is allocated to biologically relevant stimuli, has typically been studied using simplistic paradigms that do not provide any opportunity for social interaction. To study social attention in a complex setting that affords social interaction, we measured participants' looking behavior as they were sitting in a waiting room, either in the presence of a confederate posing as another research participant, or in the presence of a videotape of the same confederate. Thus, the potential for social interaction existed only when the confederate was physically present. Although participants frequently looked at the videotaped confederate, they seldom turned toward or looked at the live confederate. Ratings of participants' social skills correlated with head turns to the live, but not videotaped, confederate. Our results demonstrate the importance of studying social attention within a social context, and suggest that the mere opportunity for social interaction can alter social attention.

Sad people avoid the eyes or happy people focus on the eyes? Mood induction affects facial feature discrimination

Depressed people tend to avoid eye-contact in social situations and in experimental settings, whereas happy people actively seek eye-contact. We report an experiment in which participants made discriminations between faces that had either configural or featural changes made to the eyes, nose, or head shape. The results showed participants induced to be happy detected changes in eyes more often than participants induced to be sad, but failed to detect changes in other facial features. Sad-induced participants detected changes to the head shape but not the eyes. The results are interpreted in terms of differential use of features attended to by happy and sad participants, whereby happy people are more likely to attend to eyes during face perception than sad people.

Eye gaze during observation of static faces in deaf people

Knowing where people look when viewing faces provides an objective measure into the part of information entering the visual system as well as into the cognitive strategy involved in facial perception. In the present study, we recorded the eye movements of 20 congenitally deaf (10 male and 10 female) and 23 (11 male and 12 female) normal-hearing Japanese participants while they evaluated the emotional valence of static face stimuli. While no difference was found in the evaluation scores, the eye movements during facial observations differed among participant groups. The deaf group looked at the eyes more frequently and for longer duration than the nose whereas the hearing group focused on the nose (or the central region of face) more than the eyes. These results suggest that the strategy employed to extract visual information when viewing static faces may differ between deaf and hearing people.

WHAT PREDICTS THE OWN-AGE BIAS IN FACE RECOGNITION MEMORY?

Younger and older adults’ visual scan patterns were examined as they passively viewed younger and older neutral faces. Both participant age groups tended to look longer at their own-age as compared to other-age faces. In addition, both age groups reported more exposure to own-age than other-age individuals. Importantly, the own-age bias in visual inspection of faces and the own-age bias in self-reported amount of exposure to young and older individuals in everyday life, but not explicit age stereotypes and implicit age associations, significantly and independently predicted the own-age bias in later old/new face recognition. We suggest these findings reflect increased personal and social relevance of, and more accessible and elaborated schemas for, own-age than other-age faces.

I Know You are Beautiful Even without Looking at You: Discrimination of Facial Beauty in Peripheral Vision

Earlier research suggests that facial attractiveness may capture attention at parafovea. However, little is known about how well facial beauty can be detected at parafoveal and peripheral vision. Participants in this study judged relative attractiveness of a face pair presented simultaneously at several eccentricities from the central fixation. The results show that beauty is not only detectable at parafovea but also at periphery. The discrimination performance at parafovea was indistinguishable from the performance around the fovea. Moreover, performance was well above chance even at the periphery. The results show that the visual system is able to use the low-spatial-frequency information to appraise attractiveness. These findings not only provide an explanation why a beautiful face could capture attention when central vision is already engaged elsewhere, but also reveal the potential means by which a crowd of faces is quickly scanned for attractiveness.

Animal Recognition and Eye Movements

We assessed the importance of outline contour and individual features in mediating the recognition of animals by examining response times and eye movements in an animal-object decision task (i.e., deciding whether or not an object was an animal that may be encountered in real life). There were shorter latencies for animals as compared with nonanimals and performance was similar for shaded line drawings and silhouettes, suggesting that important information for recognition lies in the outline contour. The most salient information in the outline contour was around the head, followed by the lower torso and leg regions. We also observed effects of object orientation and argue that the usefulness of the head and lower torso/leg regions is consistent with a role for the object axis in recognition.

Altered social reward and attention in anorexia nervosa

Dysfunctional social reward and social attention are present in a variety of neuropsychiatric disorders including autism, schizophrenia, and social anxiety. Here we show that similar social reward and attention dysfunction are present in anorexia nervosa (AN), a disorder defined by avoidance of food and extreme weight loss. We measured the implicit reward value of social stimuli for female participants with (n = 11) and without (n = 11) AN using an econometric choice task and also tracked gaze patterns during free viewing of images of female faces and bodies. As predicted, the reward value of viewing bodies varied inversely with observed body weight for women with anorexia but not control women, in contrast with their explicit ratings of attractiveness. Surprisingly, women with AN, unlike control women, did not find female faces rewarding and avoided looking at both the face and eyes – independent of observed body weight. These findings suggest comorbid dysfunction in the neural circuits mediating gustatory and social reward in anorexia nervosa.

Temporal and spatial integration of face, object, and scene features in occipito-temporal cortex

In three neuroimaging experiments, face, novel object, and building stimuli were compared under conditions of restricted (aperture) viewing and normal (whole) viewing. Aperture viewing restricted the view to a single face/object feature at a time, with the subjects able to move the aperture continuously though time to reveal different features. An analysis of the proportion of time spent viewing different features showed stereotypical exploration patterns for face, object, and building stimuli, and suggested that subjects constrained their viewing to the features most relevant for recognition. Aperture viewing showed much longer response times than whole viewing, due to sequential exploration of the relevant isolated features. An analysis of BOLD activation revealed face-selective activation with both whole viewing and aperture viewing in the left and right fusiform face areas (FFA). Aperture viewing showed strong and sustained activation throughout exploration, suggesting that aperture viewing recruited similar processes as whole viewing, but for a longer time period. Face-selective recruitment of the FFA with aperture viewing suggests that the FFA is involved in the integration of isolated features for the purpose of recognition.

The early time course of compensatory face processing in congenital prosopagnosia

Background

Prosopagnosia is a selective deficit in facial identification which can be either acquired, (e.g., after brain damage), or present from birth (congenital). The face recognition deficit in prosopagnosia is characterized by worse accuracy, longer reaction times, more dispersed gaze behavior and a strong reliance on featural processing.

Methods/Principal Findings

We introduce a conceptual model of an apperceptive/associative type of congenital prosopagnosia where a deficit in holistic processing is compensated by a serial inspection of isolated, informative features. Based on the model proposed we investigated performance differences in different face and shoe identification tasks between a group of 16 participants with congenital prosopagnosia and a group of 36 age-matched controls. Given enough training and unlimited stimulus presentation prosopagnosics achieved normal face identification accuracy evincing longer reaction times. The latter increase was paralleled by an equally-sized increase in stimulus presentation times needed achieve an accuracy of 80%. When the inspection time of stimuli was limited (50ms to 750ms), prosopagnosics only showed worse accuracy but no difference in reaction time. Tested for the ability to generalize from frontal to rotated views, prosopagnosics performed worse than controls across all rotation angles but the magnitude of the deficit didn't change with increasing rotation. All group differences in accuracy, reaction or presentation times were selective to face stimuli and didn't extend to shoes.

Conclusions/Significance

Our study provides a characterization of congenital prosopagnosia in terms of early processing differences. More specifically, compensatory processing in congenital prosopagnosia requires an inspection of faces that is sufficiently long to allow for sequential focusing on informative features. This characterization of dysfunctional processing in prosopagnosia further emphasizes fast and holistic information encoding as two defining characteristics of normal face processing.

Fixation patterns during recognition of personally familiar and unfamiliar faces

Previous studies recording eye gaze during face perception have rendered somewhat inconclusive findings with respect to fixation differences between familiar and unfamiliar faces. This can be attributed to a number of factors that differ across studies: the type and extent of familiarity with the faces presented, the definition of areas of interest subject to analyses, as well as a lack of consideration for the time course of scan patterns. Here we sought to address these issues by recording fixations in a recognition task with personally familiar and unfamiliar faces. After a first common fixation on a central superior location of the face in between features, suggesting initial holistic encoding, and a subsequent left eye bias, local features were focused and explored more for familiar than unfamiliar faces. Although the number of fixations did not differ for un-/familiar faces, the locations of fixations began to differ before familiarity decisions were provided. This suggests that in the context of familiarity decisions without time constraints, differences in processing familiar and unfamiliar faces arise relatively early – immediately upon initiation of the first fixation to identity-specific information – and that the local features of familiar faces are processed more than those of unfamiliar faces.

Featural, configural, and holistic face-processing strategies evoke different scan patterns

In two experiments we investigated the role of eye movements during face processing. In experiment 1, using modified faces with primarily featural (scrambled faces) or configural (blurred faces) information as cue stimuli, we manipulated the way participants processed subsequently presented intact faces. In a sequential same-different task, participants decided whether the identity of an intact test face matched a preceding scrambled or blurred cue face. Analysis of eye movements for test faces showed more interfeatural saccades when they followed a blurred face, and longer gaze duration within the same feature when they followed scrambled faces. In experiment 2, we used a similar paradigm except that test faces were cued by intact faces, low-level blurred stimuli, or second-order scrambled stimuli (features were cut out but maintained their first-order relations). We found that in the intact condition participants performed fewer interfeatural saccades than in low-level blurred condition and had shorter gaze duration than in second-order scrambled condition. Moreover, participants fixated the centre of the test face to grasp the information from the whole face. Our findings suggest a differentiation between featural, configural, and holistic processing strategies, which can be associated with specific patterns of eye movements.

Culture shapes eye movements for visually homogeneous objects

Culture affects the way people move their eyes to extract information in their visual world. Adults from Eastern societies (e.g., China) display a disposition to process information holistically, whereas individuals from Western societies (e.g., Britain) process information analytically. In terms of face processing, adults from Western cultures typically fixate the eyes and mouth, while adults from Eastern cultures fixate centrally on the nose region, yet face recognition accuracy is comparable across populations. A potential explanation for the observed differences relates to social norms concerning eye gaze avoidance/engagement when interacting with conspecifics. Furthermore, it has been argued that faces represent a ‘special’ stimulus category and are processed holistically, with the whole face processed as a single unit. The extent to which the holistic eye movement strategy deployed by East Asian observers is related to holistic processing for faces is undetermined. To investigate these hypotheses, we recorded eye movements of adults from Western and Eastern cultural backgrounds while learning and recognizing visually homogeneous objects: human faces, sheep faces and greebles. Both group of observers recognized faces better than any other visual category, as predicted by the specificity of faces. However, East Asian participants deployed central fixations across all the visual categories. This cultural perceptual strategy was not specific to faces, discarding any parallel between the eye movements of Easterners with the holistic processing specific to faces. Cultural diversity in the eye movements used to extract information from visual homogenous objects is rooted in more general and fundamental mechanisms.

Putting culture under the 'spotlight' reveals universal information use for face recognition

Background

Eye movement strategies employed by humans to identify conspecifics are not universal. Westerners predominantly fixate the eyes during face recognition, whereas Easterners more the nose region, yet recognition accuracy is comparable. However, natural fixations do not unequivocally represent information extraction. So the question of whether humans universally use identical facial information to recognize faces remains unresolved.

Methodology/Principal Findings

We monitored eye movements during face recognition of Western Caucasian (WC) and East Asian (EA) observers with a novel technique in face recognition that parametrically restricts information outside central vision. We used ‘Spotlights’ with Gaussian apertures of 2°, 5° or 8° dynamically centered on observers' fixations. Strikingly, in constrained Spotlight conditions (2° and 5°) observers of both cultures actively fixated the same facial information: the eyes and mouth. When information from both eyes and mouth was simultaneously available when fixating the nose (8°), as expected EA observers shifted their fixations towards this region.

Conclusions/Significance

Social experience and cultural factors shape the strategies used to extract information from faces, but these results suggest that external forces do not modulate information use. Human beings rely on identical facial information to recognize conspecifics, a universal law that might be dictated by the evolutionary constraints of nature and not nurture.

Looking but not seeing: atypical visual scanning and recognition of faces in 2 and 4-year-old children with autism spectrum disorder

This study used eye-tracking to examine visual scanning and recognition of faces by 2- and 4-year-old children with autism spectrum disorder (ASD) (N = 44) and typically developing (TD) controls (N = 30). TD toddlers at both age levels scanned and recognized faces similarly. Toddlers with ASD looked increasingly away from faces with age, atypically attended to key features of faces, and were impaired in face recognition. Deficits in recognition were associated with imbalanced attention between key facial features. This study illustrates that face processing in ASD may be affected early and become further compromised with age. We propose that deficits in face processing likely impact the effectiveness of toddlers with ASD as social partners and thus should be targeted for intervention.

Deficits in cross-race face learning: insights from eye movements and pupillometry

The own-race bias (ORB) is a well-known finding wherein people are better able to recognize and discriminate own-race faces, relative to cross-race faces. In 2 experiments, participants viewed Asian and Caucasian faces, in preparation for recognition memory tests, while their eye movements and pupil diameters were continuously monitored. In Experiment 1 (with Caucasian participants), systematic differences emerged in both measures as a function of depicted race: While encoding cross-race faces, participants made fewer (and longer) fixations, they preferentially attended to different sets of features, and their pupils were more dilated, all relative to own-race faces. Also, in both measures, a pattern emerged wherein some participants reduced their apparent encoding effort to cross-race faces over trials. In Experiment 2 (with Asian participants), the authors observed the same patterns, although the ORB favored the opposite set of faces. Taken together, the results suggest that the ORB appears during initial perceptual encoding. Relative to own-race face encoding, cross-race encoding requires greater effort, which may reduce vigilance in some participants.

Anchoring gaze when categorizing faces' sex: evidence from eye-tracking data

Previous research has shown that during recognition of frontal views of faces, the preferred landing positions of eye fixations are either on the nose or the eye region. Can these findings generalize to other facial views and a simpler perceptual task? An eye-tracking experiment investigated categorization of the sex of faces seen in four views. The results revealed a strategy, preferred in all views, which consisted of focusing gaze within an 'infraorbital region' of the face. This region was fixated more in the first than in subsequent fixations. Males anchored gaze lower and more centrally than females.

Gaze behavior in face comparison: the roles of sex, task, and symmetry

Knowing where people look on a face provides an objective insight into the information entering the visual system and into cognitive processes involved in face perception. In the present study, we recorded eye movements of human participants while they compared two faces presented simultaneously. Observers' viewing behavior and performance was examined in two tasks of parametrically varying difficulty, using two types of face stimuli (sex morphs and identity morphs). The frequency, duration, and temporal sequence of fixations on previously defined areas of interest in the faces were analyzed. As was expected, viewing behavior and performance varied with difficulty. Interestingly, observers compared predominantly the inner halves of the face stimuli-a result inconsistent with the general left-hemiface bias reported for single faces. Furthermore, fixation patterns and performance differed between tasks, independently of stimulus type. Moreover, we found differences in male and female participants' viewing behaviors, but only when the sex of the face stimuli was task relevant.

The 35th Sir Frederick Bartlett Lecture: Eye movements and attention in reading, scene perception, and visual search

Eye movements are now widely used to investigate cognitive processes during reading, scene perception, and visual search. In this article, research on the following topics is reviewed with respect to reading: (a) the perceptual span (or span of effective vision), (b) preview benefit, (c) eye movement control, and (d) models of eye movements. Related issues with respect to eye movements during scene perception and visual search are also reviewed. It is argued that research on eye movements during reading has been somewhat advanced over research on eye movements in scene perception and visual search and that some of the paradigms developed to study reading should be more widely adopted in the study of scene perception and visual search. Research dealing with “real-world” tasks and research utilizing the visual-world paradigm are also briefly discussed.

Neural bases of eye and gaze processing: the core of social cognition

Eyes and gaze are very important stimuli for human social interactions. Recent studies suggest that impairments in recognizing face identity, facial emotions or in inferring attention and intentions of others could be linked to difficulties in extracting the relevant information from the eye region including gaze direction. In this review, we address the central role of eyes and gaze in social cognition. We start with behavioral data demonstrating the importance of the eye region and the impact of gaze on the most significant aspects of face processing. We review neuropsychological cases and data from various imaging techniques such as fMRI/PET and ERP/MEG, in an attempt to best describe the spatio-temporal networks underlying these processes. The existence of a neuronal eye detector mechanism is discussed as well as the links between eye gaze and social cognition impairments in autism. We suggest impairments in processing eyes and gaze may represent a core deficiency in several other brain pathologies and may be central to abnormal social cognition.

Taking a real look at social attention

The eyes of others are important to us, and we care about where they are directed. Lab-based studies often fail to capture this intuition because the studies are so simple and controlled that the situational complexity that is critical to social attention is lost. A research approach called cognitive ethology begins its investigation at the level of naturally occurring phenomena before moving into the lab. In doing so one can maintain the link between lab research and the phenomena it seeks to understand. Instances of lab failures that are offset by a cognitive ethology approach are presented and discussed.

Holistic face processing can be independent of gaze behaviour: evidence from the composite face illusion

People tend to perceive identical top halves (i.e., above the nose) of two face stimuli as being different when they are aligned with distinct bottom halves. This composite face illusion is generally considered as the most compelling evidence that facial features are integrated into a holistic representation. Here, we recorded eye-movements during the composite face illusion in a delayed matching task of top halves of faces. Behavioural results showed a strong composite face effect, participants making more mistakes and taking longer time to match two identical top halves of faces when they were aligned (vs. misaligned) with different bottom halves. Importantly, fixation sites and eye-movements were virtually identical when the top and bottom parts were aligned (composite illusion) or misaligned (no illusion), indicating that holistic face processing can be independent of gaze behaviour. These findings reinforce the view that holistic representations of individual faces can be extracted early on from information at a relatively coarse scale, independently of overt attention.

Two fixations suffice in face recognition

It is well known that there exist preferred landing positions for eye fixations in visual word recognition. However, the existence of preferred landing positions in face recognition is less well established. It is also unknown how many fixations are required to recognize a face. To investigate these questions, we recorded eye movements during face recognition. During an otherwise standard face-recognition task, subjects were allowed a variable number of fixations before the stimulus was masked. We found that optimal recognition performance is achieved with two fixations; performance does not improve with additional fixations. The distribution of the first fixation is just to the left of the center of the nose, and that of the second fixation is around the center of the nose. Thus, these appear to be the preferred landing positions for face recognition. Furthermore, the fixations made during face learning differ in location from those made during face recognition and are also more variable in duration; this suggests that different strategies are used for face learning and face recognition.

NIMBLE: a kernel density model of saccade-based visual memory

We present a Bayesian version of J. Lacroix, J. Murre, and E. Postma's (2006) Natural Input Memory (NIM) model of saccadic visual memory. Our model, which we call NIMBLE (NIM with Bayesian Likelihood Estimation), uses a cognitively plausible image sampling technique that provides a foveated representation of image patches. We conceive of these memorized image fragments as samples from image class distributions and model the memory of these fragments using kernel density estimation. Using these models, we derive class-conditional probabilities of new image fragments and combine individual fragment probabilities to classify images. Our Bayesian formulation of the model extends easily to handle multi-class problems. We validate our model by demonstrating human levels of performance on a face recognition memory task and high accuracy on multi-category face and object identification. We also use NIMBLE to examine the change in beliefs as more fixations are taken from an image. Using fixation data collected from human subjects, we directly compare the performance of NIMBLE's memory component to human performance, demonstrating that using human fixation locations allows NIMBLE to recognize familiar faces with only a single fixation.

Culture shapes how we look at faces

BACKGROUND

Face processing, amongst many basic visual skills, is thought to be invariant across all humans. From as early as 1965, studies of eye movements have consistently revealed a systematic triangular sequence of fixations over the eyes and the mouth, suggesting that faces elicit a universal, biologically-determined information extraction pattern.

METHODOLOGY/PRINCIPAL FINDINGS

Here we monitored the eye movements of Western Caucasian and East Asian observers while they learned, recognized, and categorized by race Western Caucasian and East Asian faces. Western Caucasian observers reproduced a scattered triangular pattern of fixations for faces of both races and across tasks. Contrary to intuition, East Asian observers focused more on the central region of the face.

CONCLUSIONS/SIGNIFICANCE

These results demonstrate that face processing can no longer be considered as arising from a universal series of perceptual events. The strategy employed to extract visual information from faces differs across cultures.