Spatial interference between gaze direction and gaze location: A study on the eye contact effect

Exploring the spatial interference effects elicited by social and non-social targets: A conditional accuracy function approach

Recent studies employing the spatial interference paradigm reveal qualitative differences in congruency effects between gaze and arrow targets. Typically, arrows produce a standard congruency effect (SCE), with faster responses when target direction aligns with its location. Conversely, gaze targets often lead to a reversed congruency effect (RCE), where responses are slower in similar conditions. We explored this dissociation using the Conditional Accuracy Function (CAF) to assess accuracy across reaction time bins. Using a hierarchical linear mixed modelling approach to compare cropped eyes, and full faces as social stimuli, and arrows as non-social stimuli, we synthesized findings from 11 studies, which led to three distinct models. The results showed that with non-social targets, incongruent trials exhibited lower accuracy rates in the first bin than in subsequent bins, while congruent trials maintained stable accuracy throughout the distribution. Conversely, social targets revealed a dissociation within the fastest responses; alongside a general reduction in accuracy for both congruency conditions, congruent trials resulted in even lower accuracy rates than incongruent ones. These results suggest with gaze targets that additional information, perhaps social, in addition to the automatic capture by the irrelevant target location, is being processed during the earlier stages of processing.

Temporal dynamics of activation and suppression in a spatial Stroop task: A distribution analysis on gaze and arrow targets

Directional judgments of an arrow became slower when the direction and location were incongruent in a spatial Stroop task (i.e., a standard congruency effect). In contrast, gaze judgments were slower when they were congruent (i.e., a reversed congruency effect). This study examined the reaction time (RT) distribution of interference effects in a spatial Stroop task to clarify the temporal characteristics of the standard congruency effect, which is known to be reversed for social targets, such as gaze direction. Participants responded to laterally presented targets (i.e., arrows, gaze, fish-only, and fish with mosaic) while ignoring their location. The standard congruency effect of arrows decreased as the overall RT increased, reflecting the temporal decay of automatically activated task-irrelevant codes (i.e., location). Critically, the reversed congruency effect of gaze increased as the overall RT increased. This result supports the dual-stage hypothesis and reflects the late-arriving selective inhibition of task-irrelevant codes. Similar results were replicated in Experiment 2, in which we manipulated the complexity of the backgrounds of nonsocial targets and in the reanalysis of existing data. These findings imply that the interplay between task-irrelevant activation and subsequent inhibition is modulated by specific stimulus characteristics, influencing spatial response selection.

Social face processing in chronic severe traumatic brain injury: Altered decoding of emotions and mental states but preserved gaze cueing of attention

The processing of social information transmitted by facial stimuli is altered in individuals with traumatic brain injury (TBI). This study investigated whether these alterations also affect the mechanisms underlying the orienting of visual attention in response to eye-gaze signals. TBI patients and a control group of healthy individuals matched on relevant criteria completed a spatial cueing task. In this task, a lateral visual target was presented along with a task-irrelevant face, with the gaze averted to the left or right. Arrows pointing towards the left or right were also used as non-social control stimuli. Social cognition abilities were further investigated through tests based on decoding emotional expressions and mental states conveyed by facial stimuli. The decoding of emotions and mental states was worse in the TBI group than in the control group. However, both groups demonstrated reliable and comparable orienting of attention to both eye-gaze and arrow stimuli. Despite impairments in certain aspects of social face processing among TBI patients, gaze cueing of attention appears to be preserved in this neuropsychological population.

Stretching the limits of automated symbolic orienting

Arrows trigger reflexive shifts of attention and instantiate the prototypical example of automated symbolic orienting. We conducted four experiments to further test the boundary conditions of this phenomenon. Participants discriminated a peripheral target while spatially uninformative arrows, pointing leftwards or rightwards, appeared at fixation. In all experiments, arrow direction could either randomly vary (intermixed condition) or be kept constant within a block of trials (blocked condition). Moreover, in Experiments 3 and 4, a direction word presented at the beginning of the trial informed participants about the target location with 100% certainty. Overall, the results highlighted a significant arrow-driven orienting effect in both the blocked and the intermixed conditions. The present findings support the notion that automated symbolic orienting is resistant to suppression in that it endures even when the context should stress the uninformative nature of the arrows while also creating ideal conditions to boost participants' tendency to ignore them.

Eye gaze is not unique: The reversed congruency effect on gaze and tongue targets

In the spatial Stroop task, an arrow target produces a spatial Stroop effect, whereas a gaze target elicits a reversed congruency effect. The reversed congruency effect has been explained by the unique attentional mechanisms of eye gaze. However, recent studies have shown that not only gaze but arrow targets produced a reversed congruency effect when embedded in a complex background. The present study investigated whether non-gaze targets produce a reversed congruency effect. In Experiments 1 and 2, we used the tongue, which is not commonly used to indicate spatial directions in daily life, as a target in the spatial Stroop task, in addition to the conventional gaze and arrows. In Experiment 3, we used arrow stimuli embedded in a complex background as a target. Participants judged the left/right direction of the target presented in the left or right visual field. Although arrow and gaze targets replicated previous findings (spatial Stroop and reversed congruency effect, respectively), the tongue target produced a reversed congruency effect (Experiments 1 and 2). The spatial Stroop effect of arrow targets disappeared when they were in a complex background (Experiment 3). These results are inconsistent with previous accounts emphasising the unique status of eye gaze. We propose that temporal decay of the location code and response inhibition are responsible for the reversal of spatial interference.

Testing the effects of gaze distractors with invariant spatial direction on attention cueing

In four experiments, we tested the boundary conditions of gaze cueing with reference to the resistance to suppression criterion of automaticity. Participants were asked to respond to peripheral targets preceded by a central gaze stimulus. Under one condition, gaze direction was random and uninformative with respect to target location (intermixed condition), as in the typical paradigm. Under another condition, gaze direction was uninformative and, crucially, it was also kept constant throughout the sequence of trials (blocked condition). In so doing, we aimed at maximally reducing the informative value of the gaze stimulus because gaze would not only be task-irrelevant but would also provide no sudden and unpredictable information. Across the four experiments, the results showed a strong gaze-cueing effect. More specifically, a comparable gaze cueing emerged under the blocked and intermixed conditions. These findings are consistent with the idea that gaze cueing is resistant to suppression and are discussed in relation to current views of the automaticity of gaze cueing.

Reversing the reversed congruency effect: directional salience overrides social significance in a spatial Stroop task

In a spatial Stroop task, eye-gaze targets produce a reversed congruency effect (RCE) with faster responses when gaze direction and location are incongruent than congruent. On the other hand, non-social directional targets (e.g., arrows) elicit a spatial Stroop effect (SSE). The present study examined whether other social stimuli, such as head orientation, trigger the RCE. Participants judged the target direction of the head or the gaze while ignoring its location. While the gaze target replicated the RCE, the head target produced the SSE. Moreover, the head target facilitated the overall responses relative to the gaze target. These results suggest that the head, a salient directional feature, overrides the social significance. The RCE may be specific to gaze stimuli, not to social stimuli in general. The head and gaze information differentially affect our attentional mechanisms and enable us to bring about smooth social interactions.

Perceiving social gaze produces the reversed congruency effect

Numerous studies have shown that the gaze of others produces a special attentional process, such as the eye contact effect or joint attention. This study investigated the attentional process triggered by various types of gaze stimuli (i.e., human, cat, fish, koala, and robot gaze). A total of 300 university students participated in five experiments. They performed a spatial Stroop task in which five types of gaze stimuli were presented as targets. Participants were asked to judge the direction of the target (left or right) irrespective of its location (left or right). The results showed that the social gaze targets (i.e., human and cat gaze) produced a reversed congruency effect. In contrast to the social gaze targets, the non-social gaze (i.e., fish and robot) target did not produce the reversed congruency effect (Experiments 2, 2B, 3, and 4). These results suggest that attention to the gaze of socially communicable beings (i.e., humans and cats) is responsible for the reversed congruency effect. Our findings support the notion that the theory of mind or social interaction plays an important role in producing specific attentional processes in response to gaze stimuli.

Neural basis of social attention: common and distinct mechanisms for social and nonsocial orienting stimuli

Social and nonsocial directional stimuli (such as gaze and arrows, respectively) share their ability to trigger attentional processes, although the issue of whether social stimuli generate other additional (and unique) attentional effects is still under debate. In this study, we used the spatial interference paradigm to explore, using functional magnetic resonance imaging, shared and dissociable brain activations produced by gaze and arrows. Results showed a common set of regions (right parieto-temporo-occipital) similarly involved in conflict resolution for gaze and arrows stimuli, which showed stronger co-activation for incongruent than congruent trials. The frontal eye field showed stronger functional connectivity with occipital regions for congruent as compared with incongruent trials, and this effect was enhanced for gaze as compared with arrow stimuli in the right hemisphere. Moreover, spatial interference produced by incongruent (as compared with congruent) arrows was associated with increased functional coupling between the right frontal eye field and a set of regions in the left hemisphere. This result was not observed for incongruent (as compared with congruent) gaze stimuli. The right frontal eye field also showed greater coupling with left temporo-occipital regions for those conditions in which larger conflict was observed (arrow incongruent vs. gaze incongruent trials, and gaze congruent vs. arrow congruent trials). These findings support the view that social and nonsocial stimuli share some attentional mechanisms, while at the same time highlighting other differential effects. Highlights Attentional orienting triggered by social (gaze) and nonsocial (arrow) cues is comparable. When social and nonsocial stimuli are used as targets, qualitatively different behavioral effects are observed. This study explores the neural bases of shared and dissociable neural mechanisms for social and nonsocial stimuli. Shared mechanisms were found in the functional coupling between right parieto-temporo-occipital regions. Dissociable mechanisms were found in the functional coupling between right frontal eye field and ipsilateral and contralateral occipito-temporal regions.

Are eyes special? Gaze, but not pointing gestures, elicits a reversed congruency effect in a spatial Stroop task

Gaze stimuli can shape attention in a peculiar way as compared to non-social stimuli. For instance, in a spatial Stroop task, gaze stimuli elicit a reversed congruency effect (i.e., faster responses on incongruent than on congruent trials) as compared to arrows, for which a standard congruency effect emerges. Here, we tested whether the reversed congruency effect observed for gaze can emerge for other social signals such as pointing gestures. Participants discriminated the direction (left or right) indicated by gaze and pointing finger stimuli that appeared leftwards or rightwards with respect to a central fixation spot. Arrows were also employed as control non-social stimuli. A reversed congruency effect emerged for the gaze, whereas a standard congruency effect emerged for both the pointing finger and the arrows. This suggests that the reversed congruency effect is specific to gaze stimuli and does not embrace all social signals conveying spatial information.

Explicit vs. implicit spatial processing in arrow vs. eye-gaze spatial congruency effects

Arrows and gaze stimuli lead to opposite spatial congruency effects. While standard congruency effects are observed for arrows (faster responses for congruent conditions), responses are faster when eye-gaze stimuli are presented on the opposite side of the gazed-at location (incongruent trials), leading to a reversed congruency effect (RCE). Here, we explored the effects of implicit vs. explicit processing of arrows and eye-gaze direction. Participants were required to identify the direction (explicit task) or the colour (implicit task) of left or right looking/pointing gaze or arrows, presented to either the left or right of the fixation point. When participants responded to the direction of stimuli, standard congruency effects for arrows and RCE for eye-gaze stimuli were observed. However, when participants responded to the colour of stimuli, no congruency effects were observed. These results suggest that it is necessary to explicitly pay attention to the direction of eye-gaze and arrows for the congruency effect to occur. The same pattern of data was observed when participants responded either manually or verbally, demonstrating that manual motor components are not responsible for the results observed. These findings are not consistent with some hypotheses previously proposed to explain the RCE observed with eye-gaze stimuli and, therefore, call for an alternative plausible hypothesis.

Are there quantitative differences between eye-gaze and arrow cues? A meta-analytic answer to the debate and a call for qualitative differences

Gaze acts from an early age as a cue to orient attention and, thereafter, to infer our social partners' intentions, thoughts, and emotions. Variants of the attentional orienting paradigm have been used to study the orienting capabilities associated to eye gaze. However, to date, it is still unclear whether this methodology truly assesses "social-specific" processes exclusively involved in attention to eye-gaze or the operation of domain-general attentional processes. The present study provides a comprehensive meta-analysis indicating that eye-gaze and non-social directional stimuli, such as arrows, produce equivalent attentional effects. This result casts doubt on the potential utility of the classic cueing task in revealing social-specific processes. On the other hand, we review behavioral evidence suggesting that eye-gaze stimuli may induce higher-order social processes when more specific experimental procedures that analyze qualitative rather than quantitative differences are used. These findings point to an integrated view in which domain-general and social specific processes both contribute to the attentional mechanisms induced by eye-gaze direction. Finally, some proposals about the social components specifically triggered by eye-gaze stimuli are discussed.

Integration of Facial Expression and Gaze Direction in Individuals with a High Level of Autistic Traits

BACKGROUND

We investigated whether individuals with high levels of autistic traits integrate relevant communicative signals, such as facial expression, when decoding eye-gaze direction.

METHODS

Students with high vs. low scores on the Autism Spectrum Quotient (AQ) performed a task in which they responded to the eye directions of faces, presented on the left or the right side of a screen, portraying different emotional expressions.

RESULTS

In both groups, the identification of gaze direction was faster when the eyes were directed towards the center of the scene. However, in the low AQ group, this effect was larger for happy faces than for neutral faces or faces showing other emotional expressions, whereas participants from high AQ group were not affected by emotional expressions.

CONCLUSIONS

These results suggest that individuals with more autistic traits may not integrate multiple communicative signals based on their emotional value.

What gaze adds to arrows: Changes in attentional response to gaze versus arrows in childhood and adolescence

From early ages, gaze acts as a cue to infer the interests, behaviours, thoughts and emotions of social partners. Despite sharing attentional properties with other non-social directional stimuli, such as arrows, gaze produces unique effects. A spatial interference task revealed this dissociation. The direction of arrows was identified faster on congruent than on incongruent direction-location trials. Conversely, gaze produced a reversed congruency effect (RCE), with faster identifications on incongruent than congruent trials. To determine the emergence of these gaze-specific attentional mechanisms, 214 Spanish children (4-17 years) divided into 6 age groups, performed the aforementioned task across three experiments. Results showed stimulus-specific developmental trajectories. Whereas the standard effect of arrows was unaffected by age, gaze shifted from an arrow-like effect at age 4 to a gaze-specific RCE at age 12. The orienting mechanisms shared by gaze and arrows are already present in 4-year olds and, throughout childhood, gaze becomes a special social cue with additional attentional properties. Besides orienting attention to a direction, as arrows would do, gaze might orient attention towards a specific object that would be attentionally selected. Such additional components may not fully develop until adolescence. Understanding gaze-specific attentional mechanisms may be crucial for children with atypical socio-cognitive development.

Eye Direction Detection and Perception as Premises of a Social Brain: A Narrative Review of Behavioral and Neural Data

The eyes and the gaze are important stimuli for social interaction in humans. Impaired recognition of facial identity, facial emotions, and inference of the intentions of others may result from difficulties in extracting information relevant to the eye region, mainly the direction of gaze. Therefore, a review of these data is of interest. Behavioral data demonstrating the importance of the eye region and how humans respond to gaze direction are reviewed narratively, and several theoretical models on how visual information on gaze is processed are discussed to propose a unified hypothesis. Several issues that have not yet been investigated are identified. The authors tentatively suggest experiments that might help progress research in this area. The neural aspects are subsequently reviewed to best describe the low-level and higher-level visual information processing stages in the targeted subcortical and cortical areas. A specific neural network is proposed on the basis of the literature. Various gray areas, such as the temporality of the processing of visual information, the question of salience priority, and the coordination between the two hemispheres, remain unclear and require further investigations. Finally, disordered gaze direction detection mechanisms and their consequences on social cognition and behavior are discussed as key deficiencies in several conditions, such as autism spectrum disorder, 22q11.2 deletion, schizophrenia, and social anxiety disorder. This narrative review provides significant additional data showing that the detection and perception of someone's gaze is an essential part of the development of our social brain.

A novel variation of the Stroop task reveals reflexive supremacy of peripheral over gaze stimuli in pro and anti saccades

A long-standing controversy in social attention debates whether gaze-of-another induces reflexive shifts of one's own attention. In attempting to resolve this controversy, we utilized a novel Stroop task, the PAT Stroop, in which pro- and anti-saccade (PAT) responses are made to competing gaze and peripheral stimuli. The first experiment demonstrated a "Stroop effect" for peripheral stimuli, i.e. peripheral distractors interfered with gaze triggers, but gaze distractors did not interfere with peripheral triggers. These results were replicated in the second experiment, which also negated the possibility that the mere display and practice of the "clean PAT" influenced the results. Thus, the use a new PAT Stroop task demonstrated reflexive supremacy of peripheral stimuli over gaze stimuli. This novel variant of the Stroop task demonstrated similar characteristics to the classic color naming Stroop - i.e. an asymmetrical pattern, and again showed the utility and versatility of stoop-like tasks in probing mental tasks.

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.

The influence of joint attention and partner trustworthiness on cross-modal sensory cueing

Joint attention refers to the coordinated attention between social partners to an object of shared interest, usually involving shared gaze toward the object. In the laboratory, however, joint attention is often investigated using computerized gaze cueing tasks that do not allow shared gaze. Instead, these computerized tasks require the participant to maintain fixation on the virtual partner's face, while the partner gazes to the left or right. Here we designed a modified gaze cueing task that better simulates a natural joint attention episode by allowing shared gaze, while still maintaining tight experimental control. In our computerized task the participant's gaze and the gaze of a virtual partner were manipulated independently, resulting in shared or unshared gaze. Following each gaze shift of the virtual partner a touch stimulus was delivered on one of the cheeks of the participant. We analyzed behavioral and neural (electro-encephalography) responses to the touch. Faster reaction-times and stronger lateralization of alpha power were observed when the touched cheek was in a jointly attended hemispace compared with a singly attended or unattended hemispace. Importantly, these effects were unique to joint attention and could not be explained as the additive effects of own gaze and gaze cue direction. Underlining its social nature, we found that the behavioral effect was absent when we repeated our experiment with nonsocial cues (arrows) instead of gaze cues. Furthermore, when we compared trustworthy with untrustworthy virtual partners (trustworthiness judgements based on facial appearance) we found the effect only for trustworthy and not for untrustworthy virtual partners. We conclude that joint attention based on shared gaze influences attentional orienting such that cross-modal sensory processing at the jointly attended location is facilitated, particularly when the partner is trustworthy. This indicates that social interactions and trustworthiness judgements affect cortical and behavioral responses to sensory information.

Are eyes special? Electrophysiological and behavioural evidence for a dissociation between eye-gaze and arrows attentional mechanisms

It has been proposed that attention triggered by eye-gaze may represent a unique attentional process, different from that triggered by non-social stimuli such as arrows. To investigate this issue, in the present study we compared the temporal dynamics of the conflict processing triggered by eye-gaze and arrow stimuli. We investigated the electrophysiological activity during a task in which participants were required to identify the direction of laterally presented eye-gaze or arrow targets. Opposite behavioural effects were observed: while arrows produced the typical effect, with faster responses when they were congruent with their position, eye-gaze targets produced a reversed effect with faster responses when they were incongruent. Event-related potentials showed common and dissociable congruency modulation: whereas eye-gaze and arrows showed similar effects on earlier ERP components (P1 and N1), they led to opposite effects in later components such as N2 and P3. This represents the first electrophysiological demonstration of both early shared and later dissociable congruency effects for eye-gaze and arrow stimuli.

Eye Contact and Fear of Being Laughed at in a Gaze Discrimination Task

Current approaches conceptualize gelotophobia as a personality trait characterized by a disproportionate fear of being laughed at by others. Consistently with this perspective, gelotophobes are also described as neurotic and introverted and as having a paranoid tendency to anticipate derision and mockery situations. Although research on gelotophobia has significantly progressed over the past two decades, no evidence exists concerning the potential effects of gelotophobia in reaction to eye contact. Previous research has pointed to difficulties in discriminating gaze direction as the basis of possible misinterpretations of others' intentions or mental states. The aim of the present research was to examine whether gelotophobia predisposition modulates the effects of eye contact (i.e., gaze discrimination) when processing faces portraying several emotional expressions. In two different experiments, participants performed an experimental gaze discrimination task in which they responded, as quickly and accurately as possible, to the eyes' directions on faces displaying either a happy, angry, fear, neutral, or sad emotional expression. In particular, we expected trait-gelotophobia to modulate the eye contact effect, showing specific group differences in the happiness condition. The results of Study 1 (N = 40) indicated that gelotophobes made more errors than non-gelotophobes did in the gaze discrimination task. In contrast to our initial hypothesis, the happiness expression did not have any special role in the observed differences between individuals with high vs. low trait-gelotophobia. In Study 2 (N = 40), we replicated the pattern of data concerning gaze discrimination ability, even after controlling for individuals' scores on social anxiety. Furthermore, in our second experiment, we found that gelotophobes did not exhibit any problem with identifying others' emotions, or a general incorrect attribution of affective features, such as valence, intensity, or arousal. Therefore, this bias in processing gaze might be related to the global processes of social cognition. Further research is needed to explore how eye contact relates to the fear of being laughed at.