Enfacement illusions: Filling a knowledge gap in eating disorder risk assessment, prevention, and intervention?

Body image disturbance (BID) is central to eating disorders (EDs), yet the role of self-face perception has received limited empirical attention despite rising sociocultural pressures emphasizing facial appearance through technologies such as social media. Emerging evidence suggests impairments in self-face recognition accuracy and distorted perceptions of facial appearance among individuals with EDs. Enfacement illusions, involving the experimental induction of perceived ownership over another's face, offer a novel paradigm to comprehensively investigate the perceptual multisensory integration processes underlying self-face perception disturbances in ED populations. Such an approach may hold promise for elucidating core pathological mechanisms contributing to BID and ED psychopathology. We discuss how rigorous investigation of self-face perception through the enfacement illusion paradigm represents an innovative direction of research and/or clinical application that may advance etiological models of EDs and possibly inform interventions targeting the potentially multidimensional nature of body and facial image disturbances characterizing EDs. PUBLIC SIGNIFICANCE STATEMENT: Body image disturbance is central to eating disorders (EDs), yet, the role of face-related disturbances remains critically under-investigated. After summarizing findings on face-related disturbances in EDs we propose how enfacement illusions (i.e., the experimental induction of ownership over another's face) may elucidate self-face perception disturbances in EDs, and their underlying mechanisms. Enfacement illusions may also offer an intervention to potentially address multifaceted face and body image disturbances characterizing EDs.

(No) Effects of a Self-Kindness Intervention on Self-Esteem and Visual Self-Perception: An Eye-Tracking Investigation on the Time-Course of Self-Face Viewing.

Previous research has suggested a favorable impact of self-kindness on subjective well-being. The present experiment investigated the effects of an app-assisted self-kindness intervention for increasing self-esteem and self-face gaze, and for decreasing depression. We explored self-face processing via a time-course analysis of eye-tracking data. Eighty participants (56 female, 24 male; mean age: 23.2 years) were randomly allocated to one of two intervention groups, each receiving daily instructions to enhance either self-kindness or relaxation (active control). Following a one-week intervention period, both groups reported improved self-esteem (p = .035, ηpart2 = .068) and reduced depression (p < .001, ηpart2 = .17). The duration of self-face gaze increased in both groups (p < .001, ηpart2 = .21). Self-face processing was characterized by an early automatic attention bias toward the self-face, with a subsequent reduction in self-face bias, followed in turn by an attentional self-face reapproach, and then a stable self-face bias. We thus identified a complex temporal pattern of self-face inspection, which was not specifically altered by the intervention. This research sheds light on the potential for app-assisted interventions to positively impact psychological well-being, while also highlighting the complexity of self-face processing dynamics in this context. In the future, we propose the inclusion of personalized self-kindness statements, which may amplify the benefits of these interventions.

Oxytocin enhances the triangular association among behavior, resting-state, and task-state functional connectivity.

Considerable advances in the role of oxytocin (OT) effect on behavior and the brain network have been made, but the effect of OT on the association between inter-individual differences in functional connectivity (FC) and behavior is elusive. Here, by using a face-perception task and multiple connectome-based predictive models, we aimed to (1) determine whether OT could enhance the association among behavioral performance, resting-state FC (rsFC), and task-state FC (tsFC) and (2) if so, explore the role of OT in enhancing this triangular association. We found that in the OT group, the prediction performance of using rsFC or tsFC to predict task behavior was higher than that of the PL group. Additionally, the correlation coefficient between rsFC and tsFC was substantially higher in the OT group than in the PL group. The strength of these associations could be partly explained by OT altering the brain's FCs related to social cognition and face perception in both the resting and task states, mainly in brain regions such as the limbic system, prefrontal cortex, temporal poles, and temporoparietal junction. Taken together, these results provide novel evidence and a corresponding mechanism for how neuropeptides cause increased associations among inter-individual differences across different levels (e.g., behavior and large-scale brain networks in both resting and task-state), and may inspire future research on the role of neuropeptides in the cross levels association of both clinical and nonclinical use.

Hypoactive Visual Cortex, Prefrontal Cortex and Insula during Self-Face Recognition in Adults with First-Episode Major Depressive Disorder.

Self-face recognition is a vital aspect of self-referential processing, which is closely related to affective states. However, neuroimaging research on self-face recognition in adults with major depressive disorder is lacking. This study aims to investigate the alteration of brain activation during self-face recognition in adults with first-episode major depressive disorder (FEMDD) via functional magnetic resonance imaging (fMRI); FEMDD (n = 59) and healthy controls (HC, n = 36) who performed a self-face-recognition task during the fMRI scan. The differences in brain activation signal values between the two groups were analyzed, and Pearson correlation analysis was used to evaluate the relationship between the brain activation of significant group differences and the severity of depressive symptoms and negative self-evaluation; FEMDD showed significantly decreased brain activation in the bilateral occipital cortex, bilateral fusiform gyrus, right inferior frontal gyrus, and right insula during the task compared with HC. No significant correlation was detected between brain activation with significant group differences and the severity of depression and negative self-evaluation in FEMDD or HC. The results suggest the involvement of the malfunctioning visual cortex, prefrontal cortex, and insula in the pathophysiology of self-face recognition in FEMDD, which may provide a novel therapeutic target for adults with FEMDD.

Changes in self-other boundaries modulate children's body image attitudes.

One's own face is a key distinctive feature of our physical appearance, yet multisensory visuo-tactile stimulation can alter self-other boundaries, eliciting changes in adult's self-face representation and social cognition processes. This study tested whether changing self-face representation by altering self-other boundaries with the enfacement illusion modulates body image attitudes toward others in 6-11-year-old children (N = 51; 31 girls; predominantly White). Across all ages, congruent multisensory information led to stronger enfacement (η2p = 0.06). Participants who experienced a stronger enfacement illusion showed preference for larger body size, suggesting increased positive body size attitudes. This effect was stronger in 6-7-year-olds compared to 8-9-year-olds. Thus, blurring self-other boundaries successfully modulates self-face representation and body image attitudes toward others in children. Our results suggest that increased self-resemblance through self-other blurring resulting from the enfacement illusion may reduce social comparisons between self and other and result in positive body size attitudes.

Variation in self and familiar facial recognition in bipolar disorder patients at different clinical stages.

Previous studies suggest a close relationship between self-disorders and schizophrenia or unipolar depression. However, few studies have explored the characteristics of self-processing in bipolar disorder (BD) during different clinical states. This study compared the differences in self-face recognition (SFR) among patients with bipolar mania (BPM), bipolar depression (BPD), bipolar remission (RM), and healthy controls (HC). Images of subject's own face, a familiar face, and an unfamiliar face were combined in pairs at a certain proportion to obtain three types of blended images. We then compared the tendency between BD and HC while judging two kinds of blended faces emerging from presentation software. The results showed that the BPM and BPD groups seemed to lack an advantage in self-recognition. Self-processing and familiarity processing were significantly enhanced in BPM patients, while only familiarity processing was enhanced in BPD. The severity of clinical symptoms was not significantly correlated with self-bias or familiarity bias in BD.

Cleaner fish recognize self in a mirror via self-face recognition like humans.

Some animals have the remarkable capacity for mirror self-recognition (MSR), yet any implications for self-awareness remain uncertain and controversial. This is largely because explicit tests of the two potential mechanisms underlying MSR are still lacking: mental image of the self and kinesthetic visual matching. Here, we test the hypothesis that MSR ability in cleaner fish, Labroides dimidiatus, is associated with a mental image of the self, in particular the self-face, like in humans. Mirror-naive fish initially attacked photograph models of both themselves and unfamiliar strangers. In contrast, after all fish had passed the mirror mark test, fish did not attack their own (motionless) images, but still frequently attacked those of unfamiliar individuals. When fish were exposed to composite photographs, the self-face/unfamiliar body were not attacked, but photographs of unfamiliar face/self-body were attacked, demonstrating that cleaner fish with MSR capacity recognize their own facial characteristics in photographs. Additionally, when presented with self-photographs with a mark placed on the throat, unmarked mirror-experienced cleaner fish demonstrated throat-scraping behaviors. When combined, our results provide clear evidence that cleaner fish recognize themselves in photographs and that the likely mechanism for MSR is associated with a mental image of the self-face, not a kinesthetic visual-matching model. Humans are also capable of having a mental image of the self-face, which is considered an example of private self-awareness. We demonstrate that combining mirror test experiments with photographs has enormous potential to further our understanding of the evolution of cognitive processes and private self-awareness across nonhuman animals.

Eye size recognition of self and others among people with self-face dissatisfaction.

Previous studies have shown that individuals visually recognize their eye size as larger than the actual. However, it is unclear whether this cognitive tendency occurs in people with high self-face dissatisfaction. Therefore, this study aimed to investigate whether the cognitive size of one's own and others' eyes differs according to the degree of self-face dissatisfaction. Participants comprised 32 college students (5 males, 27 females; age: 21.3 ± 2.11) who completed the Face Dissatisfaction Scale (FDS) and a face recognition memory task. The task was to choose whether their or their friends' eyes in the face photos with changed eye size were larger or smaller than their actual eye size. The cognitively equivalent eye size to the actual one was estimated from a psychophysical function. We conducted a correlation analysis of the total scores on the FDS and the point of subjective equality (PSE) of eye size. We found a high negative correlation between the FDS and the PSE of own eye size. There was also a high positive correlation between the FDS and the PSE for all others' faces. Thus, high self-face dissatisfaction is differentially associated with cognitive distortions of the face, depending on whether it is self or other.

Cultural modulation effects on the self-face advantage: Do Caucasians find their own faces faster than Chinese?

The self-face advantage (SFA) is reflected through a faster recognition of a self-face compared with familiar and unfamiliar faces. Nevertheless, as Westerners and East Asians tend to present differences in self-concept styles, it is possible that the SFA is modulated by culture. The present study explored this possibility using a visual search task. British Caucasians and Malaysian Chinese participants were asked to search for frontal view images of self, friend, and unfamiliar faces among an array of unfamiliar faces. Regardless of race, participants were more accurate and faster in searching for the own face and friend's face compared with an unfamiliar face, with no differences in the search between the own and friend's face, and these findings could not be accounted by the cultural differences in self-concept (i.e., operationalised by scores from the Independent and Interdependent Self-Concept Scale and the Horizontal and Vertical Individualism and Collectivism Scale). Altogether our results suggest that culture does not modulate the SFA and that this effect is better explained by a familiar face advantage.

An Experimental Study of Subliminal Self-Face Processing in Depersonalization-Derealization Disorder.

The self-perception or self-experience of patients with depersonalization/derealization disorder (DPD) is altered, leading to a profound disruption in self-awareness. The main aim of the study is to explore the characteristics of subliminal self-face processing in DPD patients. To our knowledge, this is the first experimental study that has measured and evaluated subliminal self-processing in DPD. To better understand this, we examined the ability of patients with DPD and healthy controls (HC) to identify pictures of faces using an experimental paradigm of breaking continuous flash suppression. There were 23 DPD outpatients from Beijing Anding Hospital, Capital Medical University and 23 matched HC who participated in this experiment. The time needed for a face to break into awareness was taken as the measure of participants' subliminal processing of that face. The results indicated that there were significant differences between the DPD patients and HC in subliminal reaction times to different faces. Under experimental conditions, the average reaction response of self-face recognition in the HC group was significantly faster than for a famous face. However, this difference was not observed in DPD patients, which means that DPD patients did not show the processing advantage of their own faces as did the HC. The results suggest a deficit in subliminal self-face processing in DPD.

A more featural based processing for the self-face: An eye-tracking study.

Studies have suggested that the holistic advantage in face perception is not always reported for the own face. With two eye-tracking experiments, we explored the role of holistic and featural processing in the processing and the recognition of self, personally familiar, and unfamiliar faces. Observers were asked to freely explore (Exp.1) and recognize (Exp.2) their own, a friend's, and an unfamiliar face. In Exp.1, self-face was fixated more and longer and there was a preference for the mouth region when seeing the own face and for the nose region when seeing a friend and unfamiliar faces. In Exp.2, the viewing strategies did not differ across all faces, with eye fixations mostly directed to the nose region. These results suggest that task demands might modulate the way that the own face is perceived and highlights the importance of considering the role of the distinct visual experience people have for the own face in the processing and recognition of the self-face.

A featural account for own-face processing? Looking for support from face inversion, composite face, and part-whole tasks.

It is widely accepted that face perception relies on holistic processing. However, this holistic advantage is not always found in the processing of the own face. Our study aimed to explore the role of holistic and featural processing in the identification of the own face, using three standard, but largely independent measures of holistic face processing: the face inversion task, the composite face task, and the part-whole task. Participants were asked to identify their face, a friend's face, and an unfamiliar face in three different experimental blocks: (a) inverted versus upright; (b) top and bottom halves of the face aligned versus misaligned; and (c) facial features presented in isolation versus whole foil face context. Inverting a face impaired its identification, regardless of the identity. However, alignment effects were only found when identifying a friend or an unfamiliar face. In addition, a stronger feature advantage (i.e., better recognition for isolated features compared to in a whole-face context) was observed for the own face compared to the friend and unfamiliar faces. Altogether, these findings suggest that the own face is processed in a more featural manner but also relies on holistic processing. This work also highlights the importance of taking into consideration that different holistic processing paradigms could tap different forms of holistic processing.

Are covered faces eye-catching for us? The impact of masks on attentional processing of self and other faces during the COVID-19 pandemic.

During the COVID-19 pandemic, we have been confronted with faces covered by surgical-like masks. This raises a question about how our brains process this kind of visual information. Thus, the aims of the current study were twofold: (1) to investigate the role of attention in the processing of different types of faces with masks, and (2) to test whether such partial information about faces is treated similarly to fully visible faces. Participants were tasked with the simple detection of self-, close-other's, and unknown faces with and without a mask; this task relies on attentional processes. Event-related potential (ERP) findings revealed a similar impact of surgical-like masks for all faces: the amplitudes of early (P100) and late (P300, LPP) attention-related components were higher for faces with masks than for fully visible faces. Amplitudes of N170 were similar for covered and fully visible faces, and sources of brain activity were located in the fusiform gyri in both cases. Linear Discriminant Analysis (LDA) revealed that irrespective of whether the algorithm was trained to discriminate three types of faces either with or without masks, it was able to effectively discriminate faces that were not presented in the training phase.

Impaired attentional bias toward one's own face in autism spectrum disorder: ERP evidence.

Converging lines of evidence seem to indicate reduced self-referential processing in individuals with autism spectrum disorder (ASD). However, processing of one's own face has rarely been investigated in the context of ASD. Thus, the aim of the present study was to elucidate the role of attentional biases in the processing of self- and other faces in ASD. To achieve this goal we presented participants with images of their own face, the face of a close-other, and famous and unknown faces in a Stroop-like paradigm. Participants (22 with ASD, 22 typically developing [TD]) were instructed to indicate the color of presented faces while EEG was recorded. Our event-related potential results clearly showed that self-face was associated with larger P3 amplitudes than all other faces in the TD group, thus indicating a strong attentional bias toward one's own face. In the ASD group, P3 to the self-face and the close-other's face did not differ, suggesting similar attentional biases in both cases. In line with these P3 findings, nonparametric cluster-based permutation tests showed an analogous pattern of results: significant clusters for the self-face compared with all other faces in the TD group, and no significant cluster in the ASD group. Overall, our findings revealed impaired attentional bias to one's own face and diminished self versus other differentiation in individuals with ASD. The similar neural underpinnings of the self-face and other faces supports previous findings indicating reduced self-prioritization among individuals with ASD.

Attractiveness Evaluation and Identity of Self-face: The Effect of Sexual Dimorphism.

The present study aims to explore the influence of masculine/feminine changes on the attractiveness evaluation of one's own face, and examine the relationship of this attractiveness evaluation and the similarities between masculine/feminine faces and original faces. A picture was taken from each participant and considered as his or her original self-face, and a male or female face with an average attractiveness score was adopted as the original other face. Masculinized and feminized transformations of the original faces (self-face, male other face, and female other face) into 100% masculine and feminine faces were produced with morphing software stepping by 2%. Thirty female participants and 30 male participants were asked to complete three tasks, i.e., to "like" or "not like" the original face judgment of a given face compared to the original face, to choose the most attractive face from a morphed facial clip, and to subjectively evaluate the attractiveness and similarity of morphed faces. The results revealed that the acceptable range of masculine/feminine transformation for self-faces was narrower than that for other faces. Furthermore, the attractiveness ratings for masculinized or femininized self-faces were correlated with the similarity scores of the faces with the original self-faces. These findings suggested that attractiveness enhancement of self-face through masculinity/femininity must be within reasonable extent and take into account the similarity between the modified faces and the original self-face.

Self-Processing and Self-Face Reaction Time Latencies: A Review.

In this article, we detail the advantages of self-face identification latencies over more traditional tests of mirror self-recognition. Using reaction time latencies (measured in milliseconds) to identify different dimensions of the self, instead of relying on a simple dichotomous pass/fail mirror mark-test outcome, enables investigators to examine individual differences in self-processing time. This is a significant methodological step forward with important implications. The point of departure for our article is to detail research we and others have conducted on latencies for self-face identification, to show how self-processing occurs in the right side of the brain, how schizophrenia is a self-processing disorder, how self-face reaction time latencies implicate the existence of an underlying multiple modal self-processing system, and to explore ideas for future research.

The Self in the Mind's Eye: Revealing How We Truly See Ourselves Through Reverse Correlation.

Is there a way to visually depict the image people "see" of themselves in their minds' eyes? And if so, what can these mental images tell us about ourselves? We used a computational reverse-correlation technique to explore individuals' mental "self-portraits" of their faces and body shapes in an unbiased, data-driven way (total N = 116 adults). Self-portraits were similar to individuals' real faces but, importantly, also contained clues to each person's self-reported personality traits, which were reliably detected by external observers. Furthermore, people with higher social self-esteem produced more true-to-life self-portraits. Unlike face portraits, body portraits had negligible relationships with individuals' actual body shape, but as with faces, they were influenced by people's beliefs and emotions. We show how psychological beliefs and attitudes about oneself bias the perceptual representation of one's appearance and provide a unique window into the internal mental self-representation-findings that have important implications for mental health and visual culture.

Early Capture of Attention by Self-Face: Investigation Using a Temporal Order Judgment Task.

Earlier work on self-face processing has reported a bias in the processing of self-face result in faster response to self-face in comparison to other familiar and unfamiliar faces (termed as self-face advantage or SFA). Even though most studies agree that the SFA occurs due to an attentional bias, there is little agreement regarding the stage at which it occurs. While a large number of studies show self-face influencing processing later at disengagement stage, early event-related potential components show differential activity for the self-face suggesting that SFA occurs early. We address this contradiction using a cueless temporal order judgment task that allows us to investigate early perceptual processing, while bias due to top-down expectation is controlled. A greater shift in point of subjective simultaneity for self-face would indicate a greater processing advantage at early perceptual stage. With help of two experiments, we show an early perceptual advantage for self-face, compared to both a friend's face and an unfamiliar face (Experiment 1). This advantage is present even when the effect of criterion shift is minimized (Experiment 2). Interestingly, the magnitude of advantage is similar for self-friend and self-unfamiliar pair. The evidence from the two experiments suggests early capture of attention as a likely reason for the SFA, which is present for the self-face but not for other familiar faces.

The upside-down self: One's own face recognition is affected by inversion.

One's own face is recognized more efficiently than any other face, although the neural mechanisms underlying this phenomenon remain poorly understood. Considering the extensive visual experience that we have with our own face, some authors have proposed that self-face recognition involves a more analytical perceptual strategy (i.e., based on face features) than other familiar faces, which are commonly processed holistically (i.e., as a whole). However, this hypothesis has not yet been tested with brain activity data. In the present study, we employed an inversion paradigm combined with event-related potential (ERP) recordings to investigate whether the self-face is processed more analytically. Sixteen healthy participants were asked to identify their own face and a familiar face regardless of its orientation, which could either be upright or inverted. ERP analysis revealed an enhanced amplitude and a delayed latency for the N170 component when faces were presented in an inverted orientation. Critically, both the self and a familiar face were equally vulnerable to the inversion effect, suggesting that the self-face is not processed more analytically than a familiar face. In addition, we replicated the recent finding that the attention-related P200 component is a specific neural index of self-face recognition. Overall, our results suggest that the advantage for self-face processing might be better explained by the engagement of self-related attentional mechanisms than by the use of a more analytical visuoperceptual strategy.

Self-Face Activates the Dopamine Reward Pathway without Awareness.

The self-face advantage has been demonstrated not only at the supraliminal level, but also at the subliminal level. However, it remains unclear whether subliminal self-face processing involves the same neural networks as those for supraliminal self-face processing. Here, we show that the ventral tegmental area, a center of the dopamine reward pathway, exhibited greater activation to subliminal presentations of the self-face than those of the others' faces, whereas subliminal presentations of the others' faces induced activation in the amygdala, which generally responds to unfamiliar information. This self-other difference in brain response was consistently observed even when the facial configuration was modified without changing the shape of the facial parts. The present findings suggest that the dopamine reward pathway is involved in automatic self-advantage in face processing, and the subliminal self-other facial discrimination does not depend on information of the precise facial configuration.