Configural Processing in the Perception of Eye-Gaze Direction

Explicit and implicit mentalization of patients with first-episode schizophrenia: a study of self-referential gaze perception with eye movement analysis using hidden Markov models

Mentalizing impairment is one of the core features of schizophrenia, and bias judgement of others' gaze as self-directing is common to schizophrenia patients. In this case-control study, 30 patients with first-episode schizophrenia (FES) and 30 matched healthy controls were assigned gaze perception tasks with variable stimulus presentation times (300 ms and no time limit) to determine the presence of self-referential gaze perception (SRGP) bias. The eye movement pattern during the task were tracked and data were analysed using hidden Markov models (HMMs). The SRGP involves reporting of others' gaze intent and was used as a measurement of explicit mentalizing process. Eye movement measurement represents automated visual attention pattern and was considered as a measurement of implicit mentalizing process. The patients with FES had significantly more SRGP bias than the controls in the 300 ms condition but not in the no-time-limit condition. Social cognitive function was related to SRGP bias in the patient group. Two distinct eye movement patterns were identified: eye-focused and nose-focused. Significant group differences in eye movement patterns in the 300 ms condition were found with more controls had eye-focused pattern. Social anxiety symptoms were related to the nose-focused pattern, positive psychotic symptoms were related to the eye-focused pattern, and depressive symptoms were related to less consistent eye movement patterns. No significant relationship was found between SRGP bias and eye movement patterns. The dissociation between explicit and implicit mentalizing processes with different cognitive and symptom dimensions associated with the two processes suggests the presence of different mechanisms.

How facial masks alter the interaction of gaze direction, head orientation, and emotion recognition

The COVID-19 pandemic has altered the way we interact with each other: mandatory mask-wearing obscures facial information that is crucial for emotion recognition. Whereas the influence of wearing a mask on emotion recognition has been repeatedly investigated, little is known about the impact on interaction effects among emotional signals and other social signals. Therefore, the current study sought to explore how gaze direction, head orientation, and emotional expression interact with respect to emotion perception, and how these interactions are altered by wearing a face mask. In two online experiments, we presented face stimuli from the Radboud Faces Database displaying different facial expressions (anger, fear, happiness, neutral, and sadness), gaze directions (−13°, 0°, and 13°), and head orientations (−45°, 0°, and 45°) – either without (Experiment 1) or with mask (Experiment 2). Participants categorized the displayed emotional expressions. Not surprisingly, masks impaired emotion recognition. Surprisingly, without the mask, emotion recognition was unaffected by averted head orientations and only slightly affected by gaze direction. The mask strongly interfered with this ability. The mask increased the influence of head orientation and gaze direction, in particular for the emotions that were poorly recognized with mask. The results suggest that in case of uncertainty due to ambiguity or absence of signals, we seem to unconsciously factor in extraneous information.

Inversion Reduces Sensitivity to Complex Emotions in Eye Regions

Inferring humans’ complex emotions is challenging but can be done with surprisingly limited emotion signals, including merely the eyes alone. Here, we test for a role of lower-level perceptual processes involved in such sensitivity using the well-validated Reading the Mind in the Eyes task. Over three experiments, we manipulated configural processing to show that it contributes to sensitivity to complex emotion from human eye regions. Specifically, inversion, a well-established manipulation affecting configural processing, undermined sensitivity to complex emotions in eye regions (Experiments 1-3). Inversion extended to undermine sensitivity to nonmentalistic information from human eye regions (gender; Experiment 2) but did not extend to affect sensitivity to attributes of nonhuman animals (Experiment 3). Taken together, the current findings provide evidence for the novel hypothesis that configural processing facilitates sensitivity to complex emotions conveyed by the eyes via the broader extraction of socially relevant information.

Visual Information Routes in the Posterior Dorsal and Ventral Face Network Studied with Intracranial Neurophysiology and White Matter Tract Endpoints

Occipitotemporal regions within the face network process perceptual and socioemotional information, but the dynamics and information flow between different nodes of this network are still debated. Here, we analyzed intracerebral EEG from 11 epileptic patients viewing a stimulus sequence beginning with a neutral face with direct gaze. The gaze could avert or remain direct, while the emotion changed to fearful or happy. N200 field potential peak latencies indicated that face processing begins in inferior occipital cortex and proceeds anteroventrally to fusiform and inferior temporal cortices, in parallel. The superior temporal sulcus responded preferentially to gaze changes with augmented field potential amplitudes for averted versus direct gaze, and large effect sizes relative to other network regions. An overlap analysis of posterior white matter tractography endpoints (from 1066 healthy brains) relative to active intracerebral electrodes in the 11 patients showed likely involvement of both dorsal and ventral posterior white matter pathways. Overall, our data provide new insight into the timing of face and social cue processing in the occipitotemporal brain and anchor the superior temporal cortex in dynamic gaze processing.

Meeting another's gaze shortens subjective time by capturing attention

Gaze directed at the observer (direct gaze) is an important and highly salient social signal with multiple effects on cognitive processes and behavior. It is disputed whether the effect of direct gaze is caused by attentional capture or increased arousal. Time estimation may provide an answer because attentional capture predicts an underestimation of time whereas arousal predicts an overestimation. In a temporal bisection task, observers were required to classify the duration of a stimulus as short or long. Stimulus duration was selected randomly between 988 and 1479 ms. When gaze was directed at the observer, participants underestimated stimulus duration, suggesting that effects of direct gaze are caused by attentional capture, not increased arousal. Critically, this effect was limited to dynamic stimuli where gaze appeared to move toward the participant. The underestimation was present with stimuli showing a full face, but also with stimuli showing only the eye region, inverted faces and high-contrast eye-like stimuli. However, it was absent with static pictures of full faces and dynamic nonfigurative stimuli. Because the effect of direct gaze depended on motion, which is common in naturalistic scenes, more consideration needs to be given to the ecological validity of stimuli in the study of social attention.

Self-referential gaze perception of patients with schizophrenia and its relationship with symptomatology and cognitive functions

Self-referential gaze perception (SRGP)-the perception that others' gaze is towards oneself-is a core experience in patients with schizophrenia, and may be related to common delusional themes such as delusions of reference. Studies exploring SRGP bias in schizophrenia are limited and results have been inconsistent, particularly regarding its relationship with symptomatology and cognition. Seventy-five patients with schizophrenia-spectrum disorders (25 with high level of reference delusion, 25 with low reference delusion and 25 in clinical remission) and 25 matched healthy controls were compared in a gaze perception task to judge whether averted gaze with varied ambiguity was directed at them. All subjects were assessed with delusion and reference ideations and cognitive functions. Psychotic symptoms were assessed in patients. Gaze perception analysis adopted both behavioural and psychophysical approaches. Group differences and predictors of SRGP in ambiguous and unambiguous conditions were investigated. Both groups of symptomatic patients displayed higher ambiguous SRGP rate, and the group with high reference delusions showed more unambiguous SRGP bias. Cognitive functions were negatively associated with SRGP rate while positive and negative symptoms were positively associated. Cognitive function was the only significant predictor for ambiguous-SRGP rate. Patients with psychotic symptoms have hypermentalization of gaze perception as towards oneself, whereas patients with delusions of reference have more profound bias in gaze perception. General cognition is implicated in SRGP rate. Future studies could investigate interventions with targeted psychopathological profiles by improving non-social cognitive functions to test the hypothesis that cognitive functioning is related to SRGP bias and delusional beliefs.

How ubiquitous is the direct-gaze advantage? Evidence for an averted-gaze advantage in a gaze-discrimination task

Human eye gaze conveys an enormous amount of socially relevant information, and the rapid assessment of gaze direction is of particular relevance in order to adapt behavior accordingly. Specifically, previous research demonstrated evidence for an advantage of processing direct (vs. averted) gaze. The present study examined discrimination performance for gaze direction (direct vs. averted) under controlled presentation conditions: Using a backward-masking gaze-discrimination task, photographs of faces with direct and averted gaze were briefly presented, followed by a mask stimulus. Additionally, effects of facial context on gaze discrimination were assessed by either presenting gaze direction in isolation (i.e., by only showing the eye region) or in the context of an upright or inverted face. Across three experiments, we consistently observed a facial context effect with highest discrimination performance for faces presented in upright position, lower performance for inverted faces, and lowest performance for eyes presented in isolation. Additionally, averted gaze was generally responded to faster and with higher accuracy than direct gaze, indicating an averted-gaze advantage. Overall, the results suggest that direct gaze is not generally associated with processing advantages, thereby highlighting the important role of presentation conditions and task demands in gaze perception.

Quantifying the Wollaston Illusion

In the early 19th century, William H. Wollaston impressed the Royal Society of London with engravings of portraits. He manipulated facial features, such as the nose, and thereby dramatically changed the perceived gaze direction, although the eye region with iris and eye socket had remained unaltered. This Wollaston illusion has been replicated numerous times but never with the original stimuli. We took the eyes (pupil and iris) from Wollaston's most prominent engraving and measured their perceived gaze direction in an analog fashion. We then systematically added facial features (eye socket, eyebrows, nose, skull, and hair). These features had the power to divert perceived gaze direction by up to 20°, which confirms Wollaston's phenomenal observation. The effect can be thought of as an attractor effect, that is, cues that indicate a slight change in head orientation have the power to divert perceived gaze direction.

The role of the motion cue in the dynamic gaze-cueing effect: A study of the lateralized ERPs

When face was inverted, dynamic gaze cues could still effectively direct attention despite the disruption of configural face processing, but the static gaze cues could not. The present study investigated the role of the motion cue in the dynamic Gaze-Cueing Effect (GCE). With schematic and real faces, we employed the gaze-cueing paradigm to examine the differences among three kinds of cues (static gaze cue, dynamic gaze cue and motion cue) based on behavioral results and event-related potentials. Behavioral results revealed significant GCE in all conditions. In the schematic face group, the motion cue (two symmetrical dots shifting slightly to the side) induced a significantly smaller GCE than the dynamic gaze cues (two symmetrical dots moving within a rounded circle), while in the real face group, the motion cue (that is, the inverted-face gaze cue) remained a strong GCE compared with other conditions. With regard to the ERP results, we found the early directing attention negativity (EDAN), which was sensitive to voluntary cues (e.g. arrow cue) rather than gaze cue, in the schematic motion cue condition, but not in the inverted-face gaze cue condition. We supposed that the motion cue (real face) could activate the configural face processing even when the face is inverted. This finding supported that EDAN reflected a cue-triggered attention shift.

Task Dependent Effects of Head Orientation on Perceived Gaze Direction

The perception of gaze direction involves the integration of a number of sensory cues exterior to the eye-region. The orientation of the head is one such cue, which has an overall repulsive effect on the perceived direction of gaze. However, in a recent experiment, we found the measured effect of head orientation on perceived gaze direction differed within subjects, depending on whether a single- or two-interval task design was employed. This suggests a potential difference in the way the orientation of the head is integrated into the perception of gaze direction across tasks. Four experiments were conducted to investigate this difference. The first two experiments showed that the difference was not the result of some interaction between stimuli in the two-interval task, but rather, a difference between the types of judgment being made across tasks, where observers were making a directional (left/right) judgment in the single-interval task, and a non-directional (direct/indirect gaze) judgment in the two-interval task. A third experiment showed that this difference does not arise from observers utilizing a non-directional cue to direct gaze (the circularity of the pupil/iris) in making their non-directional judgments. The fourth experiment showed no substantial differences in the duration of evidence accumulation and processing between judgments, suggesting that observers are not integrating different sensory information across tasks. Together these experiments show that the sensory information from head orientation is flexibly weighted in the perception of gaze direction, and that the purpose of the observer, in sampling gaze information, can influence the consequent perception of gaze direction.

How wide is the cone of direct gaze?

The cone of direct gaze refers to the range of gaze deviations an observer accepts as looking directly at them. Previous experiments have calculated the width of the cone of direct gaze using the gaze deviations actually presented to the observer, however, there is considerable evidence that observers actually perceive gaze to be systematically more deviated than actually presented. Here, we examine the width of the cone of direct gaze in units of perceived gaze deviation. In doing so, we are able to disambiguate differences in width both within and between observers that are due to differences in their perception of gaze and due to differences in what observers consider to be looking at them. We suggest that this line of inquiry can offer further insight into the perception of gaze direction, and how this perception may differ in clinical populations.

Early and late cortical responses to directly gazing faces are task dependent

Gender categorisation of human faces is facilitated when gaze is directed toward the observer (i.e., a direct gaze), compared with situations where gaze is averted or the eyes are closed (Macrae, Hood, Milne, Rowe, & Mason, Psychological Science, 13(5), 460-464, 2002). However, the temporal dynamics underlying this phenomenon remain to some extent unknown. Here, we used electroencephalography (EEG) to assess the neural correlates of this effect, focusing on the event-related potential (ERP) components known to be sensitive to gaze perception (i.e., P1, N170, and P3b). We first replicated the seminal findings of Macrae et al. (2002, Experiment 1) regarding facilitated gender discrimination, and subsequently measured the underlying neural responses. Our data revealed an early preferential processing of direct gaze as compared with averted gaze and closed eyes at the P1, which reverberated at the P3b (Experiment 2). Critically, using the same material, we failed to reproduce these effects when gender categorisation was not required (Experiment 3). Taken together, our data confirm that direct gaze enhances the early P1, as well as later cortical responses to face processing, although the effect appears to be task dependent.

Pointing perception is precise

The spontaneity and ease with which we point understates the gesture's significance to understanding cognition. Onset of pointing in infancy predicts early word acquisition and signals a capacity for shared intentionality. Yet, notwithstanding its importance, there is little research on the perception of pointing and its referents. Here we show that perceptual acuity for discerning where another person is pointing is remarkably accurate. Thresholds, as low as 0.5° of visual angle across an interpersonal distance of ∼2 m, are modulated by the referent's location in space and the hand used to point and remain constant when the pointer's eyes are occluded from view and when 'embodiment' cues are enhanced or minimized. Pointing with the index finger not only directs attention toward a general region of space but the morphology of arm, hand and finger can be used to discern the location of the pointer's attention with precision.

Detecting and identifying offset gaze

A number of experiments have demonstrated that observers can accurately identify stimuli that they fail to detect (Rollman and Nachmias, 1972; Harris and Fahle, 1995; Allik et al. 1982, 2014). Using a 2x2AFC double judgements procedure, we demonstrated an analogous pattern of performance in making judgements about the direction of eye gaze. Participants were shown two faces in succession: one with direct gaze and one with gaze offset to the left or right. We found that they could identify the direction of gaze offset (left/right) better than they could detect which face contained the offset gaze. A simple Thurstonian model, under which the detection judgement is shown to be more computationally complex, was found to explain the empirical data. A further experiment incorporated metacognitive ratings into the double judgements procedure to measure observers' metacognitive awareness (Meta-d') across the two judgements and to assess whether observers were aware of the evidence for offset gaze when detection performance was at and below threshold. Results suggest that metacognitive awareness is tied to performance, with approximately equal Meta-d' across the two judgements, when sensitivity is taken into account. These results show that both performance and metacognitive awareness rely not only on the strength of sensory evidence but also on the computational complexity of the decision, which determines the relative distance of that evidence from the decision axes.

The influences of face inversion and facial expression on sensitivity to eye contact in high-functioning adults with autism spectrum disorders

We examined the influences of face inversion and facial expression on sensitivity to eye contact in high-functioning adults with and without an autism spectrum disorder (ASD). Participants judged the direction of gaze of angry, fearful, and neutral faces. In the typical group only, the range of directions of gaze leading to the perception of eye contact (the cone of gaze) was narrower for upright than inverted faces. In both groups, the cone of gaze was wider for angry faces than for fearful or neutral faces. These results suggest that in high-functioning adults with ASD, the perception of eye contact is not tuned to be finer for upright than inverted faces, but that information is nevertheless integrated across expression and gaze direction.

Autistic traits influence gaze-oriented attention to happy but not fearful faces

The relationship between autistic traits and gaze-oriented attention to fearful and happy faces was investigated at the behavioral and neuronal levels. Upright and inverted dynamic face stimuli were used in a gaze-cueing paradigm while event related potentials (ERPs) were recorded. Participants responded faster to gazed-at than to non-gazed-at targets, and this gaze orienting effect (GOE) diminished with inversion, suggesting it relies on facial configuration. It was also larger for fearful than happy faces but only in participants with high autism-spectrum quotient (AQ) scores. While the GOE to fearful faces was of similar magnitude regardless of AQ scores, a diminished GOE to happy faces was found in participants with high AQ scores. At the ERP level, a congruency effect on target-elicited P1 component reflected enhanced visual processing of gazed-at targets. In addition, cue-triggered early directing attention negativity and anterior directing attention negativity reflected, respectively, attention orienting and attention holding at gazed-at locations. These neural markers of spatial attention orienting were not modulated by emotion and were not found in participants with high AQ scores. Together, these findings suggest that autistic traits influence attention orienting to gaze and its modulation by social emotions such as happiness.

What is social about social perception research?

A growing consensus in social cognitive neuroscience holds that large portions of the primate visual brain are dedicated to the processing of social information, i.e., to those aspects of stimuli that are usually encountered in social interactions such as others' facial expressions, actions, and symbols. Yet, studies of social perception have mostly employed simple pictorial representations of conspecifics. These stimuli are social only in the restricted sense that they physically resemble objects with which the observer would typically interact. In an equally important sense, however, these stimuli might be regarded as "non-social": the observer knows that they are viewing pictures and might therefore not attribute current mental states to the stimuli or might do so in a qualitatively different way than in a real social interaction. Recent studies have demonstrated the importance of such higher-order conceptualization of the stimulus for social perceptual processing. Here, we assess the similarity between the various types of stimuli used in the laboratory and object classes encountered in real social interactions. We distinguish two different levels at which experimental stimuli can match social stimuli as encountered in everyday social settings: (1) the extent to which a stimulus' physical properties resemble those typically encountered in social interactions and (2) the higher-level conceptualization of the stimulus as indicating another person's mental states. We illustrate the significance of this distinction for social perception research and report new empirical evidence further highlighting the importance of mental state attribution for perceptual processing. Finally, we discuss the potential of this approach to inform studies of clinical conditions such as autism.

Electrophysiological responses in mothers to their own and unfamiliar child's gaze information

An attachment bond between a mother and her child is one of the most intimate human relationships. It is important for a mother to be sensitive to her child's gaze direction because exchanging gaze information plays a vital role in their relationship. Furthermore, recent studies have revealed differential neural activation patterns in mothers when presented the faces of their own children or the unfamiliar child of other people. Based on these findings, in the present study, we investigated whether mothers show differential neural responses to gaze information of their own child compared to that of an unfamiliar child. To this end, event-related-potentials elicited by the faces of one's own or an unfamiliar child with straight or averted gaze directions were measured using an oddball-paradigm. The results showed that peak amplitudes of the N170 component were enlarged by viewing the straight gazes compared to the averted gazes of one's own child, but not of an unfamiliar child. When the gaze was directed straight, the P3 amplitude elicited by one's own child's face is smaller than that elicited by an unfamiliar child's face. P3s elicited in viewing one's own child's face with averted gaze and in viewing an unfamiliar child's face with straight gaze were positively correlated with state-anxiety. These results bolster the hypothesis that processing the gaze information of one's own child elicits differential neural activation compared to the gaze information of an other person's unfamiliar child at both perceptual and evaluative stages of face processing.

The development of perceptual expertise for faces and objects in autism spectrum conditions

Previous research indicates that individuals with autism spectrum conditions (ASC) do not develop face expertise to the same extent as typical individuals. Yet it remains unclear whether this atypicality is specific to faces or related to more pervasive perceptual or cognitive deficits involved in the actual process of gaining expertise. To address this question, we examined the extent to which adults with ASC were capable of developing expertise with non-face objects. To become experts, all participants completed a 2-week training program with novel objects, known as Greebles. Level of expertise was assessed throughout training by measuring the ability to identify Greebles on an individual level. The perceptual strategies acquired as a result of expertise were measured through an inversion effect task completed before and after training, in which performance with upright Greebles and faces was compared to performance with inverted Greebles and faces. After expertise training, it was found that individuals in both the ASC and the typical group successfully achieved expertise and showed an enhanced Greeble inversion effect as a result of training. The development of an inversion effect with Greebles suggests that individuals with ASC may employ the same processing strategies as the typical group. Although exploratory, these findings have implications for understanding the nature of the face processing deficit in ASC as well as offering potential insights into face processing interventions for individuals with ASC.

Is it in the eyes? Dissociating the role of emotion and perceptual features of emotionally expressive faces in modulating orienting to eye gaze

This study investigated the role of the eye region of emotional facial expressions in modulating gaze orienting effects. Eye widening is characteristic of fearful and surprised expressions and may significantly increase the salience of perceived gaze direction. This perceptual bias rather than the emotional valence of certain expressions may drive enhanced gaze orienting effects. In a series of three experiments involving low anxiety participants, different emotional expressions were tested using a gaze-cueing paradigm. Fearful and surprised expressions enhanced the gaze orienting effect compared with happy or angry expressions. Presenting only the eye regions as cueing stimuli eliminated this effect whereas inversion globally reduced it. Both inversion and the use of eyes only attenuated the emotional valence of stimuli without affecting the perceptual salience of the eyes. The findings thus suggest that low-level stimulus features alone are not sufficient to drive gaze orienting modulations by emotion. Rather, they interact with the emotional valence of the expression that appears critical. The study supports the view that rapid processing of fearful and surprised emotional expressions can potentiate orienting to another person's averted gaze in non-anxious people.

The effect of face eccentricity on the perception of gaze direction

The perception of a looker's gaze direction depends not only on iris eccentricity (the position of the looker's irises within the sclera) but also on the orientation of the lookers' head. One among several potential cues of head orientation is face eccentricity, the position of the inner features of the face (eyes, nose, mouth) within the head contour, as viewed by the observer. For natural faces this cue is confounded with many other head-orientation cues, but in schematic faces it can be studied in isolation. Salient novel illustrations of the effectiveness of face eccentricity are 'Necker faces', which involve equal iris eccentricities but multiple perceived gaze directions. In four experiments, iris and face eccentricity in schematic faces were manipulated, revealing strong and consistent effects of face eccentricity on perceived gaze direction, with different types of tasks. An additional experiment confirmed the 'Mona Lisa' effect with this type of stimuli. Face eccentricity most likely acted as a simple but robust cue of head turn. A simple computational account of combined effects of cues of eye and head turn on perceived gaze direction is presented, including a formal condition for the perception of direct gaze. An account of the 'Mona Lisa' effect is presented.

The rapid development of explicit gaze judgment ability at 3 years

Two studies examined development of the ability to judge what another person is looking at. In Study 1, 54 2- to 4-year-olds judged where someone was looking in real-life, photograph, and drawing formats. A minority of 2-year-olds, but a majority of older children, passed all tasks, suggesting that the ability arises at around 3 years of age. Study 2 examined the fine-grained gaze judgment of 76 3- to 6-year-olds and 15 adults using gaze differences of 10 degrees and 15 degrees . Development of gaze judgment was gradual, from chance at 3 years of age to near adult-level performance at 6 years of age. Although performance was better when a congruent head turn was included, 3-year-olds were still at chance on 10 degrees head turn trials. The findings suggest that the ability to explicitly judge gaze is novel at 3 years of age and develops slowly thereafter. Therefore, the ability does not develop out of earlier gaze following. General implications for the evolution and development of gaze processing are discussed.

The role of gaze direction in face viewpoint aftereffect

Face viewpoint aftereffect is a visual illusion that, after adaptation to a face side view, the perceived view direction of the same face subsequently presented near its front view is biased in a direction opposite to that of the adapted view. Eye gaze is a unique component in face not only because its direction is relatively independent of face view direction, but also because it is a primary cue for conveying social attention. Here, we studied the contribution of gaze direction adaptation to the formation of face viewpoint aftereffect. We found that a tiny (in terms of relative area) change of gaze direction in adapting face stimuli could induce a dramatic reduction in the magnitude of face viewpoint aftereffect. However, vertical inversion of the face stimuli almost abolished the reduction. Implications of these findings about face view representation and gaze direction representation are discussed.

A role for eyebrows in regulating the visibility of eye gaze direction

The human eye is unique amongst those of primates in having white sclera against which the dark iris is clearly visible. This high-contrast structure makes the gaze direction of a human potentially easily perceptible to others. For a social creature such as a human, the ability to perceive the direction of another's gaze may be very useful, since gaze usually signals attention. We report data showing that the accuracy of gaze deviation detection is independent of viewing distance up to a certain critical distance, beyond which it collapses. This is, of itself, surprising since most visual tasks are performed better at closer viewing distances. Our data also show that the critical distance, but not accuracy, is affected by the position of the eyebrows so that lowering the eyebrows reduces the critical distance. These findings show that mechanisms exist by which humans could expand or restrict the availability of their gaze direction to others. A way to regulate the availability of the gaze direction signal could be an advantage. We show that an interpretation of eyebrow function in these terms provides a novel explanation for several well-known eyebrow actions, including the eyebrow flash.

The effects of eye and face inversion on the early stages of gaze direction perception--an ERP study

Eye direction perception is highly important for social cognition. However, the neural mechanism underlying gaze direction perception has not been well elucidated. The present study aimed to examine the specific neural mechanism of gaze direction perception by investigating how the event related potential components, which presumably reflect the early stages of face processing, are affected by inverting eye region and face context, i.e., facial parts other than eye region. The results showed that eye region inversion significantly delayed the peak latency of the N170 component. At the same time, N170 latency was also delayed by inverting face context alone. Moreover, we observed that the P100 latency was delayed by inverting the eye region in an upright face context, but not in an inverted face context. We suggest that N170 reflects the eye-sensitive cortical response, but also the processing of other facial regions, and that the processing of eye region begins at an early stage of face processing, around 100 ms after stimulus onset.

Gaze cueing of attention: visual attention, social cognition, and individual differences

During social interactions, people's eyes convey a wealth of information about their direction of attention and their emotional and mental states. This review aims to provide a comprehensive overview of past and current research into the perception of gaze behavior and its effect on the observer. This encompasses the perception of gaze direction and its influence on perception of the other person, as well as gaze-following behavior such as joint attention, in infant, adult, and clinical populations. Particular focus is given to the gaze-cueing paradigm that has been used to investigate the mechanisms of joint attention. The contribution of this paradigm has been significant and will likely continue to advance knowledge across diverse fields within psychology and neuroscience.

Meanings in motion and faces: developmental associations between the processing of intention from geometrical animations and gaze detection accuracy

Aspects of face processing, on the one hand, and theory of mind (ToM) tasks, on the other hand, show specific impairment in autism. We aimed to discover whether a correlation between tasks tapping these abilities was evident in typically developing children at two developmental stages. One hundred fifty-four normal children (6-8 years and 16-18 years) and 13 high-IQ autistic children (11-17 years) were tested on a range of face-processing and IQ tasks, and a ToM test based on the attribution of intentional movement to abstract shapes in a cartoon. By midchildhood, the ability accurately and spontaneously to infer the locus of attention of a face with direct or averted gaze was specifically associated with the ability to describe geometrical animations using mental state terms. Other face-processing and animation descriptions failed to show the association. Autistic adolescents were impaired at both gaze processing and ToM descriptions, using these tests. Mentalizing and gaze perception accuracy are associated in typically developing children and adolescents. The findings are congruent with the possibility that common neural circuitry underlies, at least in part, processing implicated in these tasks. They are also congruent with the possibility that autism may lie at one end of a developmental continuum with respect to these skills, and to the factor(s) underpinning them.

Do the upright eyes have it?

Eye contact is crucial for social communication. A perceived direct gaze facilitates detection, whereas face inversion diminishes this facilitative effect (Senju, Hasegawa, & Tojo, 2005). In the present study, we adopted a visual search paradigm to investigate why a direct gaze facilitates detection in an upright face, but not in an upside-down face. Upright eyes were found to facilitate detection even when other parts of the face were inverted or absent, whereas inverted eyes had no effect on search performance. A critical role for the morphological information of upright eyes, which can be distorted by "eye inversion," in direct gaze processing is suggested.

Gaze cues evoke both spatial and object-centered shifts of attention

When someone observes another individual suddenly shifting gaze, the observer's attention automatically and rapidly orients to the same location. Such gaze cuing of attention has properties similar to those of exogenous cuing. We investigated whether gaze cuing is also like exogenous cuing in that it is observed for both spatial and object-/head-centered frames of reference. That is, when the face that produces the gaze cue is presented on its side, tilted 90 degrees from upright, will attention be simultaneously directed to where the eyes would have been looking if the face had been presented upright and toward the actual spatial direction of gaze? It is demonstrated that gaze cues do indeed orient attention in both spatial and object-centered frames, that these effects are of similar magnitude, and that such orienting is relatively rapidly computed.

Objects Capture Perceived Gaze Direction

The interpretation of another person's eye gaze is a key element of social cognition. Previous research has established that this ability develops early in life and is influenced by the person's head orientation, as well as local features of the person's eyes. Here we show that the presence of objects in the attended space also has an impact on gaze interpretation. Eleven normal adults identified the fixation points of photographed faces with a mouse cursor. Their responses were systematically biased toward the locations of nearby objects. This capture of perceived gaze direction probably reflects the attribution of intentionality and has methodological implications for research on gaze perception.

The inversion effect on gaze perception reflects processing of component information

When faces are turned upside-down they are much more difficult to recognize than other objects. This "face inversion effect" has often been explained in terms of configural processing, which is impaired when faces are rotated away from the upright. Here we report a "gaze inversion effect" and discuss whether it is related to configural face processing of the whole face. Observers reported the gaze locations of photographed upright or inverted faces. When whole faces were presented, we found an inversion effect both for constant errors and observer sensitivity. These results were closely replicated when only the eyes were visible. Together, our findings suggest that gaze processing is largely based on component-based information from the eye region. Processing this information is orientation-sensitive and does not seem to rely on configural processing of the whole face.

Effect of image orientation on the eye direction aftereffect

After observing a face with the eyes looking to the left or right (adaptation stimulus), the perception of the eye direction of the subsequent face (test stimulus) is biased in the opposite direction of the adapted eye direction; this is called the eye direction aftereffect (EDAE). In the present study, the adaptation stimuli were rotated 90 degrees (clockwise or counterclockwise) or 180 degrees relative to the viewer. The EDAE was measured using upright test stimuli. For the 90 degrees rotation, prior observation of the 'leftward' and 'rightward' eye directions biased the perceived eye directions of the upright test stimuli to the right and left, respectively. These results suggest that the adaptation was induced utilizing an object-based (or face-based) reference frame. For the 180 degrees rotation, however, the results suggest that the adaptation was induced in a viewer-centered reference frame. The involvement of an object-based reference frame suggests that the EDAE reflected the adaptation of a relatively higher-level mechanism at least when the rotation angle from the upright position did not exceed 90 degrees .

Interactions between the processing of gaze direction and facial expression

In this article, we explored the relationship between the processing of facial expression and the processing of gaze direction. In Experiment 1, participants were unable to ignore gaze while classifying expression-or to ignore expression while classifying gaze. This suggests that the processing of expression and the processing of gaze are interdependent. In Experiment 2, the faces were inverted to isolate configural from part-based contributions to this interdependence. Inversion had a striking effect on expression judgments, which could now be processed independently of gaze, but not on gaze judgments, which were still influenced by expression, even when photos that contained only the eye region of faces were presented (Experiment 4). In Experiment 3 the processing of expression was found to be sensitive to even small variations in the direction of gaze. These results suggest that the processing underlying judgments of expression is configural and entails an obligatory computation of gaze direction. Judgments of gaze direction, however, are carried out in a part-based manner using local features around the eyes and are insensitive to the configural aspects of facial processing.

Orienting to Eye Gaze and Face Processing

The author conducted 7 experiments to examine possible interactions between orienting to eye gaze and specific forms of face processing. Participants classified a letter following either an upright or inverted face with averted, uninformative eye gaze. Eye gaze orienting effects were recorded for upright and inverted faces, irrespective of whether the faces were simple, schematic faces or more realistic faces. In contrast, inversion affected orienting to targets appearing along the vertical axis. Switching the contrast between the iris and sclera reversed orienting to eye gaze. Lifting the eyelid to expose more of the iris-sclera contrast led to a potentiation of orienting to eye gaze. Raising the eyebrow alone without the eyelid did not affect orienting. The findings suggest that local perceptual information is critical for orienting to eye gaze and that the effect can occur with a degree of independence from certain types of face processing.

The influence of head contour and nose angle on the perception of eye-gaze direction

We report seven experiments that investigate the influence that head orientation exerts on the perception of eye-gaze direction. In each of these experiments, participants were asked to decide whether the eyes in a brief and masked presentation were looking directly at them or were averted. In each case, the eyes could be presented alone, or in the context of congruent or incongruent stimuli In Experiment 1A, the congruent and incongruent stimuli were provided by the orientation of face features and head outline. Discrimination of gaze direction was found to be better when face and gaze were congruent than in both of the other conditions, an effect that was not eliminated by inversion of the stimuli (Experiment 1B). In Experiment 2A, the internal face features were removed, but the outline of the head profile was found to produce an identical pattern of effects on gaze discrimination, effects that were again insensitive to inversion (Experiment 2B) and which persisted when lateral displacement of the eyes was controlled (Experiment 2C). Finally, in Experiment 3A, nose angle was also found to influence participants' ability to discriminate direct gaze from averted gaze, but here the effect was eliminated by inversion of the stimuli (Experiment 3B). We concluded that an image-based mechanism is responsible for the influence of head profile on gaze perception, whereas the analysis of nose angle involves the configural processing of face features.

Eye direction aftereffect

Three experiments using computer-generated human figures showed that after a prolonged observation of eyes looking to the left (or right), eyes looking directly toward the viewer appeared directed to the right (or left). Observation of an arrow pointing left or right did not induce this aftereffect on the perceived eye direction. Happy faces produced the aftereffect more effectively than surprised faces, even though the image features of the eyes were identical for both the happy and the surprised faces. These results suggest that the eye direction aftereffect may reflect the adaptation of relatively higher-level mechanisms analyzing the other's eye direction.