Discrimination Of Gaze Direction Research Articles

The Timing of Gaze Direction Perception: ERP Decoding and Task Modulation

Distinguishing the direction of another person's eye gaze is extremely important in everyday social interaction, as it provides critical information about people's attention and, therefore, intentions. The temporal dynamics of gaze processing have been investigated using event-related potentials (ERPs) recorded with electroencephalography (EEG). However, the moment at which our brain distinguishes the gaze direction (GD), irrespectively of other facial cues, remains unclear. To solve this question, the present study aimed to investigate the time course of gaze direction processing, using an ERP decoding approach, based on the combination of a support vector machine and error-correcting output codes. We recorded EEG in young healthy subjects, 32 of them performing GD detection and 34 conducting face orientation tasks. Both tasks presented 3D realistic faces with five different head and gaze orientations each: 30°, 15° to the left or right, and 0°. While the classical ERP analyses did not show clear GD effects, ERP decoding analyses revealed that discrimination of GD, irrespective of head orientation, started at 140 ms in the GD task and at 120 ms in the face orientation task. GD decoding accuracy was higher in the GD task than in the face orientation task and was the highest for the direct gaze in both tasks. These findings suggest that the decoding of brain patterns is modified by task relevance, which changes the latency and the accuracy of GD decoding.

Impaired Facial Emotion Recognition and Gaze Direction Detection in Mild Alzheimer's Disease: Results from the PACO Study.

Facial emotion recognition (FER) and gaze direction (GD) identification are core components of social cognition, possibly impaired in many psychiatric or neurological conditions. Regarding Alzheimer's disease (AD), current knowledge is controversial. The aim of this study was to explore FER and GD identification in mild AD compared to healthy controls. 180 participants with mild AD drawn from the PACO study and 74 healthy elderly controls were enrolled. Participants were asked to complete three socio-cognitive tasks: face sex identification, recognition of facial emotions (fear, happiness, anger, disgust) expressed at different intensities, and GD discrimination. Multivariate analyses were conducted to compare AD participants and healthy controls. Sex recognition was preserved. GD determination for subtle deviations was impaired in AD. Recognition of prototypically expressed facial emotions was preserved while recognition of degraded facial emotions was impacted in AD participants compared to controls. Use of multivariate analysis suggested significant alteration of low-expressed fear and disgust recognition in the AD group. Our results showed emotion recognition and GD identification in patients with early-stage AD compared to elderly controls. These impairments could be the object of specific therapeutic interventions such as social cognition remediation or raising awareness of primary caregivers to improve the quality of life of patients with early AD.

Perception of Gaze Direction in Glaucoma: A Study on Social Cognition.

Discriminating quickly where another person's gaze is directed is a key component of social interaction, as gaze direction conveys information about others' intentions (approach or avoidance) and shift in gaze is used in group conversation. This study shows that patients with glaucoma are delayed in their discrimination of gaze direction. The purpose of this study was to investigate whether glaucoma affects the perception of gaze direction. Twenty-four patients with open-angle glaucoma, 24 age-matched controls, and 20 young normally sighted controls were presented with faces displayed centrally for 200 milliseconds. The gaze could either be direct or averted, and the head could be a frontal view or a rotated view. Half of the participants in each group were asked to press a key only for faces with a direct gaze. The other half responded for a face with an averted gaze. The orientation of the head had to be ignored. Accuracy was greater than 90% correct for all three groups. We found no difference in performance between young and older controls, except for shorter response times for the frontal view than for the rotated face in young participants. Patients with glaucoma needed on average 140 milliseconds longer to decide if the gaze was averted than for the direct gaze, and they were less accurate than controls in perceiving the gaze as direct when the head was rotated. Patients with glaucoma often experience impaired vision due to a reduced sensitivity in central vision. Although lower central sensitivity had little effect on their ability to discriminate gaze orientation, they required on average 140 milliseconds longer than age-matched controls to perceive an averted gaze.

Joint attention facilitates observed gaze direction discrimination

Efficiently judging where someone else is looking is important for social interactions, allowing us a window into their mental state by establishing joint attention. Previous work has shown that judging the gaze direction of a non-foveally presented face is facilitated when the eyes of that face are directed towards the centre of the scene. This finding has been interpreted as an example of the human bias for misattributing observed ambiguous gaze signals as self-directed eye-contact. To test this interpretation against an alternative hypothesis that the facilitation is instead driven by the establishment of joint attention, we conducted two experiments in which we varied the participants' fixation location. In both experiments, we replicated the previous finding of facilitated gaze discrimination when the participants fixated centrally. However, this facilitation was abolished when participants fixated peripheral fixation crosses (Experiment 1) and reversed when participants fixated peripheral images of real-world objects (Experiment 2). Based on these data, we propose that the facilitation effect is consistent with the interpretation that gaze discrimination is facilitated when joint attention is established. This finding therefore extends previous work showing that engaging in joint attention facilitates a range of social cognitive processes.

Perception of eye gaze direction in a case of acquired prosopagnosia

The ability to perceive the direction of eye gaze is critical in social settings. Brain lesions in the superior temporal sulcus (STS) impair this ability. We investigated the perception of gaze direction of PS, a patient suffering from acquired prosopagnosia (Rossion et al., 2003). Despite lesions in the face network, the STS was spared in PS. We assessed perception of gaze direction in PS with upright, inverted, and contrast-reversed faces. Compared to the performance of 11 healthy women matched for age and education, PS demonstrated abnormal discrimination of gaze direction with upright and contrast-reversed faces, but not with inverted faces. Our findings suggest that the inability of the patient to process faces holistically weakened her perception of gaze direction, especially in demanding tasks.

How social exclusion modulates social information processing: A behavioural dissociation between facial expressions and gaze direction

Social exclusion is a painful experience that is felt as a threat to the human need to belong and can lead to increased aggressive and anti-social behaviours, and results in emotional and cognitive numbness. Excluded individuals also seem to show an automatic tuning to positivity: they tend to increase their selective attention towards social acceptance signals. Despite these effects known in the literature, the consequences of social exclusion on social information processing still need to be explored in depth. The aim of this study was to investigate the effects of social exclusion on processing two features that are strictly bound in the appraisal of the meaning of facial expressions: gaze direction and emotional expression. In two experiments (N = 60, N = 45), participants were asked to identify gaze direction or emotional expressions from facial stimuli, in which both these features were manipulated. They performed these tasks in a four-block crossed design after being socially included or excluded using the Cyberball game. Participants’ empathy and self-reported emotions were recorded using the Empathy Quotient (EQ) and PANAS questionnaires. The Need Threat Scale and three additional questions were also used as manipulation checks in the second experiment. In both experiments, excluded participants showed to be less accurate than included participants in gaze direction discrimination. Modulatory effects of direct gaze (Experiment 1) and sad expression (Experiment 2) on the effects of social exclusion were found on response times (RTs) in the emotion recognition task. Specific differences in the reaction to social exclusion between males and females were also found in Experiment 2: excluded male participants tended to be less accurate and faster than included male participants, while excluded females showed a more accurate and slower performance than included female participants. No influence of social exclusion on PANAS or EQ scores was found. Results are discussed in the context of the importance of identifying gaze direction in appraisal theories.

Asymmetry in Gaze Direction Discrimination Between the Upper and Lower Visual Fields.

Previous research has shown that gaze direction can only be accurately discriminated within parafoveal limits (∼5° eccentricity) along the horizontal visual field. Beyond this eccentricity, head orientation seems to influence gaze discrimination more than iris cues. The present study examined gaze discrimination performance in the upper visual field (UVF) and lower visual field (LVF), and whether head orientation affects gaze judgments beyond parafoveal vision. Direct and averted gaze faces, in frontal and deviated head orientations, were presented for 150 ms along the vertical meridian while participants maintained central fixation during gaze discrimination judgments. Gaze discrimination was above chance level at all but one eccentricity for the two gaze-head congruent conditions. In contrast, for the incongruent conditions, gaze was discriminated above chance only from -1.5° to +3°, with an asymmetry between the UVF and LVF. Beyond foveal vision, response rates were biased toward head orientation rather than iris eccentricity, occurring in the LVF for both head orientations, and in the UVF for frontal head views. These findings suggest that covert processing of gaze direction involves the integration of eyes and head cues, with congruency of these two social cues driving response differences between the LVF and the UVF.

Motion influences gaze direction discrimination and disambiguates contradictory luminance cues.

In two experiments, we investigated the role of apparent motion in discriminating left/right gaze deviation judgments. We demonstrated that discrimination accuracy and response confidence was significantly higher when the eyes were moved to the left or right, compared to when the eyes were presented in their final shifted position (static images). To dissociate the role of motion signals from luminance signals, gaze stimuli were also presented in reverse contrast. Replicating past studies polarity reversal had a profound and detrimental effect on gaze discrimination in static images, although, intriguingly, while response confidence remained low, participant performance improved as gaze angle increased. In striking contrast to these data, polarity reversal had no negative effect on performance when the eyes were moved. We discuss these findings in the context of a multiple-cue account of gaze perception.

The Mona Lisa effect: neural correlates of centered and off-centered gaze.

The Mona Lisa effect describes the phenomenon when the eyes of a portrait appear to look at the observer regardless of the observer's position. Recently, the metaphor of a cone of gaze has been proposed to describe the range of gaze directions within which a person feels looked at. The width of the gaze cone is about five degrees of visual angle to either side of a given gaze direction. We used functional magnetic resonance imaging to investigate how the brain regions involved in gaze direction discrimination would differ between centered and decentered presentation positions of a portrait exhibiting eye contact. Subjects observed a given portrait's eyes. By presenting portraits with varying gaze directions-eye contact (0°), gaze at the edge of the gaze cone (5°), and clearly averted gaze (10°), we revealed that brain response to gaze at the edge of the gaze cone was similar to that produced by eye contact and different from that produced by averted gaze. Right fusiform gyrus and right superior temporal sulcus showed stronger activation when the gaze was averted as compared to eye contact. Gaze sensitive areas, however, were not affected by the portrait's presentation location. In sum, although the brain clearly distinguishes averted from centered gaze, a substantial change of vantage point does not alter neural activity, thus providing a possible explanation why the feeling of eye contact is upheld even in decentered stimulus positions.

Erratum: Perception of Direct Gaze Does Not Require Focus of Attention

Previous research using averted (e.g., leftward or rightward) gaze indicates that gaze perception requires a focus of attention. However, direct gaze, compared with averted gaze, is processed in the brain preferentially and enhances cognitive functions. Thus, it is necessary to use direct gaze to investigate whether gaze perception is possible without focused attention. We conducted a dual-task paradigm in which attention was drawn away from gaze. Results showed performance on gaze-direction discrimination (direct vs. averted gaze) in the dual-task condition was only slightly lower than in the single-task condition; participants were able to discriminate direct from averted gaze without focusing their attention in a similar manner to when they did focus their attention. In contrast, when participants discriminated between averted gazes (leftward and rightward), performance dropped to near-chance levels. It was concluded that gaze perception does not require a focus of attention for direct gaze.

Perception of Direct Gaze Does Not Require Focus of Attention

Previous research using averted (e.g., leftward or rightward) gaze indicates that gaze perception requires a focus of attention. However, direct gaze, compared with averted gaze, is processed in the brain preferentially and enhances cognitive functions. Thus, it is necessary to use direct gaze to investigate whether gaze perception is possible without focused attention. We conducted a dual-task paradigm in which attention was drawn away from gaze. Results showed performance on gaze-direction discrimination (direct vs. averted gaze) in the dual-task condition was only slightly lower than in the single-task condition; participants were able to discriminate direct from averted gaze without focusing their attention in a similar manner to when they did focus their attention. In contrast, when participants discriminated between averted gazes (leftward and rightward), performance dropped to near-chance levels. It was concluded that gaze perception does not require a focus of attention for direct gaze.

Explicit versus implicit gaze processing assessed by ERPs

Gaze processing was investigated using event-related potentials in two different tasks in which front-view and 3/4-view faces were presented, with eyes gazing straight ahead or averted. Task alternated between an explicit gaze direction judgment and a judgment on head orientation where gaze was irrelevant. Accuracy and reaction times were affected by the congruency of gaze and head directions in both tasks suggesting gaze was processed implicitly in the head orientation task. In both tasks, larger P1 and N170 were found for 3/4-view faces compared to front-view faces that were not due to the luminance or contrast of the pictures. The N170 was also larger for averted than straight gaze but for front-view faces only. In contrast, larger amplitudes for straight than averted gaze were reliably measured around 400–600 ms regardless of head orientation or task demands, and likely reflected the outcome of gaze processing. The results suggest that head orientation and gaze direction discrimination occur regardless of task demands and interact at the decision making level. Neural markers of head orientation occur before those for gaze direction and the early structural encoding stages of face processing are view-dependant.

Gaze but not arrows: A dissociative impairment after right superior temporal gyrus damage

Superior temporal sulcus (STS) activation has consistently been demonstrated in the normal brain when viewing eyes, and thus this area is implicated as a gaze processing region in humans. In a recent report, we have presented a case, M.J., with a well-circumscribed lesion to the right superior temporal gyrus (STG), who demonstrated impaired discrimination of gaze direction. In the aim to make distinct whether this impairment is unique to gaze, we have applied a spatial cueing paradigm established by Kingstone and colleagues. In our experiment, pictorial gaze and symmetrical arrows were centrally presented as non-predictive, spatial cues in detecting peripheral targets. Fifteen normal subjects and M.J. participated in the experiment. In concordance with previous reports, controls demonstrated a significant facilitation of reaction times in detecting targets cued by congruent gaze/arrows, compared with incongruent cues. In striking contrast, M.J. showed no such congruency advantage for gaze, in the face of a normal congruency advantage for arrows. We have demonstrated that a circumscribed lesion to the right STG impairs the ability to utilize biological directional information such as gaze, but leaves the non-biological counterpart (arrows) intact. This dissociation implies that indeed, the STS specializes in processing gaze.

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.