Individual differences in eye movements during face identification reflect observer-specific optimal points of fixation

Examining holistic processing strategies in dogs and humans through gaze behavior

Extensive studies have shown that humans process faces holistically, considering not only individual features but also the relationships among them. Knowing where humans and dogs fixate first and the longest when they view faces is highly informative, because the locations can be used to evaluate whether they use a holistic face processing strategy or not. However, the conclusions reported by previous eye-tracking studies appear inconclusive. To address this, we conducted an experiment with humans and dogs, employing experimental settings and analysis methods that can enable direct cross-species comparisons. Our findings reveal that humans, unlike dogs, preferentially fixated on the central region, surrounded by the inner facial features, for both human and dog faces. This pattern was consistent for initial and sustained fixations over seven seconds, indicating a clear tendency towards holistic processing. Although dogs did not show an initial preference for what to look at, their later fixations may suggest holistic processing when viewing faces of their own species. We discuss various potential factors influencing species differences in our results, as well as differences compared to the results of previous studies.

Neural Speech Tracking Contribution of Lip Movements Predicts Behavioral Deterioration When the Speaker's Mouth Is Occluded

Observing lip movements of a speaker facilitates speech understanding, especially in challenging listening situations. Converging evidence from neuroscientific studies shows stronger neural responses to audiovisual stimuli compared with audio-only stimuli. However, the interindividual variability of this contribution of lip movement information and its consequences on behavior are unknown. We analyzed source-localized magnetoencephalographic responses from 29 normal-hearing participants (12 females) listening to audiovisual speech, both with and without the speaker wearing a surgical face mask, and in the presence or absence of a distractor speaker. Using temporal response functions to quantify neural speech tracking, we show that neural responses to lip movements are, in general, enhanced when speech is challenging. After controlling for speech acoustics, we show that lip movements contribute to enhanced neural speech tracking, particularly when a distractor speaker is present. However, the extent of this visual contribution to neural speech tracking varied greatly among participants. Probing the behavioral relevance, we demonstrate that individuals who show a higher contribution of lip movements in terms of neural speech tracking show a stronger drop in comprehension and an increase in perceived difficulty when the mouth is occluded by a surgical face mask. In contrast, no effect was found when the mouth was not occluded. We provide novel insights on how the contribution of lip movements in terms of neural speech tracking varies among individuals and its behavioral relevance, revealing negative consequences when visual speech is absent. Our results also offer potential implications for objective assessments of audiovisual speech perception.

Preferred fixation position and gaze location: Two factors modulating the composite face effect

Humans consistently land their first saccade to a face at a preferred fixation location (PFL). Humans also typically process faces as wholes, as evidenced by perceptual effects such as the composite face effect (CFE). However, not known is whether an individual's tendency to process faces as wholes varies with their gaze patterns on the face. Here, we investigated variation of the CFE with the PFL. We compared the strength of the CFE for two groups of observers who were screened to have their PFLs either higher up, closer to the eyes, or lower on the face, closer to the tip of the nose. During the task, observers maintained their gaze at either their own group's mean PFL or at the other group's mean PFL. We found that the top half of the face elicits a stronger CFE than the bottom half. Further, the strength of the CFE was modulated by the distance of the PFL from the eyes, such that individuals with a PFL closer to the eyes had a stronger CFE than those with a PFL closer to the mouth. Finally, the top-half CFE for both upper-lookers and lower-lookers was abolished when they fixated at a non-preferred location on the face. Our findings show that the CFE relies on internal face representations shaped by the long-term use of a consistent oculomotor strategy to view faces.

Gaze-action coupling, gaze-gesture coupling, and exogenous attraction of gaze in dyadic interactions

In human interactions, gaze may be used to acquire information for goal-directed actions, to acquire information related to the interacting partner's actions, and in the context of multimodal communication. At present, there are no models of gaze behavior in the context of vision that adequately incorporate these three components. In this study, we aimed to uncover and quantify patterns of within-person gaze-action coupling, gaze-gesture and gaze-speech coupling, and coupling between one person's gaze and another person's manual actions, gestures, or speech (or exogenous attraction of gaze) during dyadic collaboration. We showed that in the context of a collaborative Lego Duplo-model copying task, within-person gaze-action coupling is strongest, followed by within-person gaze-gesture coupling, and coupling between gaze and another person's actions. When trying to infer gaze location from one's own manual actions, gestures, or speech or that of the other person, only one's own manual actions were found to lead to better inference compared to a baseline model. The improvement in inferring gaze location was limited, contrary to what might be expected based on previous research. We suggest that inferring gaze location may be most effective for constrained tasks in which different manual actions follow in a quick sequence, while gaze-gesture and gaze-speech coupling may be stronger in unconstrained conversational settings or when the collaboration requires more negotiation. Our findings may serve as an empirical foundation for future theory and model development, and may further be relevant in the context of action/intention prediction for (social) robotics and effective human-robot interaction.

Fixation patterns in pairs of facial expressions-preferences of self-critical individuals

So far, studies have revealed some differences in how long self-critical individuals fixate on specific facial expressions and difficulties in recognising these expressions. However, the research has also indicated a need to distinguish between the different forms of self-criticism (inadequate or hated self), the key underlying factor in psychopathology. Therefore, the aim of the current research was to explore fixation patterns for all seven primary emotions (happiness, sadness, fear, disgust, contempt, anger, and surprise) and the neutral face expression in relation to level of self-criticism by presenting random facial stimuli in the right or left visual field. Based on the previous studies, two groups were defined, and the pattern of fixations and eye movements were compared (high and low inadequate and hated self). The research sample consisted of 120 adult participants, 60 women and 60 men. We used the Forms of Self-Criticizing and Self-Reassuring Scale to measure self-criticism. As stimuli for the eye-tracking task, we used facial expressions from the Umeå University Database of Facial Expressions database. Eye movements were recorded using the Tobii X2 eye tracker. Results showed that in highly self-critical participants with inadequate self, time to first fixation and duration of first fixation was shorter. Respondents with higher inadequate self also exhibited a sustained pattern in fixations (total fixation duration; total fixation duration ratio and average fixation duration)-fixation time increased as self-criticism increased, indicating heightened attention to facial expressions. On the other hand, individuals with high hated self showed increased total fixation duration and fixation count for emotions presented in the right visual field but did not differ in initial fixation metrics in comparison with high inadequate self group. These results suggest that the two forms of self-criticism - inadequate self and hated self, may function as distinct mechanisms in relation to emotional processing, with implications for their role as potential transdiagnostic markers of psychopathology based on the fixation eye-tracking metrics.

Specified functions of the first two fixations in face recognition: Sampling the general-to-specific facial information

Visual perception is enacted and constrained by the constantly moving eyes. Although it is well known that the first two fixations are crucial for face recognition, the function of each fixation remains unspecified. Here we demonstrate a central-to-divergent pattern of the two fixations and specify their functions: Fix I clustered along the nose bridge to cover the broad facial information; Fix II diverged to eyes, nostrils, and lips to get the local information. Fix II correlated more than Fix I with the differentiating information between faces and contributed more to recognition responses. While face categories can be significantly discriminated by Fix II's but not Fix I's patterns alone, the combined patterns of the two yield better discrimination. Our results suggest a functional division and collaboration of the two fixations in sampling the general-to-specific facial information and add to understanding visual perception as an active process undertaken by structural motor programs.

Individual gaze shapes diverging neural representations

Complex visual stimuli evoke diverse patterns of gaze, but previous research suggests that their neural representations are shared across brains. Here, we used hyperalignment to compare visual responses between observers viewing identical stimuli. We find that individual eye movements enhance cortical visual responses but also lead to representational divergence. Pairwise differences in the spatial distribution of gaze and in semantic salience predict pairwise representational divergence in V1 and inferior temporal cortex, respectively. This suggests that individual gaze sculpts individual visual worlds.

The Observer's Lens: The Impact of Personality Traits and Gaze on Facial Impression Inferences

Previous studies on facial impression inference have focused on the physical features of faces, with only a few considering the effects of the observer. This study explored how participants' personality traits directly and indirectly affect the impression inference of human faces. Specifically, we examined how observers' personality traits impact their eye movements, which in turn influence impression inferences. Experiment 1 found relationships between participants' personality traits and eye movements, but these did not significantly impact impression inferences. In Experiment 2, we manipulated observers' observational behavior to control for the potential interactive effect between facial features and participants' eye movements during impression inference. This manipulation suggested that focusing on different areas of faces leads to different impression inferences. It also suggests that the same person might have different impressions of the exact same face by changing their observational behavior. These results deepen our understanding of the impact of facial features and participants' personality traits on impression inferences, indicating that observers' personality traits and observational behavior play a significant role in impression formation.

Anatomical variants of acne differ in their impact on social perception

BACKGROUND

Acne negatively affects quality of life, however quality-of-life scores poorly correlate with disease severity scores. Previous research demonstrated existence of facial areas in which skin lesions have greater impact on gaze patterns. Therefore, we hypothesized that anatomical variants of acne may be perceived differently.

OBJECTIVES

The aim was to investigate effect of anatomical variants of acne on natural gaze patterns and resulting impact on social perception of acne patients.

METHODS

We tracked eye movements of participants viewing neutral and emotional faces with acne. Images were rated for acne-related visual disturbance, and emotional faces were rated for valence intensity. Respondents of an online survey were asked to rate their perception of pictured individuals' personality traits.

RESULTS

All faces with acne were perceived as less attractive and received poorer personality judgements with mid-facial acne presenting smallest deviation from healthy faces. T-zone and mixed acne exhibited the least significant difference in respondents gaze behaviour pattern from each other. In addition, there was no significant difference in respondents' grading of acne visual disturbance or ratings for attractiveness, success and trustworthiness. U-zone adult female acne was rated as the most visually disturbing and received the lowest scores for attractiveness. Happy faces with adult female acne were rated as less happy compared to other acne variants and clear-skin faces.

CONCLUSIONS

Anatomic variants of acne have a distinct impact on gaze patterns and social perception. Adult female acne has the strongest negative effect on recognition of positive emotions in affected individuals, attractiveness ratings and forming social impressions. If perioral acne lesions are absent, frontal lesions determine impact of acne on social perception irrespective of the presence of mid-facial lesions. This perceptive hierarchy should be taken into consideration while deciding treatment goals in acne patients, prioritizing achieving remission in perioral and frontal area.

When knowing the activity is not enough to predict gaze

It is reasonable to assume that where people look in the world is largely determined by what they are doing. The reasoning is that the activity determines where it is useful to look at each moment in time. Assuming that it is vital to accurately judge the positions of the steps when navigating a staircase, it is surprising that people differ a lot in the extent to which they look at the steps. Apparently, some people consider the accuracy of peripheral vision, predictability of the step size, and feeling the edges of the steps with their feet to be good enough. If so, occluding part of the view of the staircase and making it more important to place one's feet gently might make it more beneficial to look directly at the steps before stepping onto them, so that people will more consistently look at many steps. We tested this idea by asking people to walk on staircases, either with or without a tray with two cups of water on it. When carrying the tray, people walked more slowly, but they shifted their gaze across steps in much the same way as they did when walking without the tray. They did not look at more steps. There was a clear positive correlation between the fraction of steps that people looked at when walking with and without the tray. Thus, the variability in the extent to which people look at the steps persists when one makes walking on the staircase more challenging.

Understanding Human Cognition Through Computational Modeling

One important goal of cognitive science is to understand the mind in terms of its representational and computational capacities, where computational modeling plays an essential role in providing theoretical explanations and predictions of human behavior and mental phenomena. In my research, I have been using computational modeling, together with behavioral experiments and cognitive neuroscience methods, to investigate the information processing mechanisms underlying learning and visual cognition in terms of perceptual representation and attention strategy. In perceptual representation, I have used neural network models to understand how the split architecture in the human visual system influences visual cognition, and to examine perceptual representation development as the results of expertise. In attention strategy, I have developed the Eye Movement analysis with Hidden Markov Models method for quantifying eye movement pattern and consistency using both spatial and temporal information, which has led to novel findings across disciplines not discoverable using traditional methods. By integrating it with deep neural networks (DNN), I have developed DNN+HMM to account for eye movement strategy learning in human visual cognition. The understanding of the human mind through computational modeling also facilitates research on artificial intelligence's (AI) comparability with human cognition, which can in turn help explainable AI systems infer humans' belief on AI's operations and provide human-centered explanations to enhance human-AI interaction and mutual understanding. Together, these demonstrate the essential role of computational modeling methods in providing theoretical accounts of the human mind as well as its interaction with its environment and AI systems.

Explanation strategies in humans versus current explainable artificial intelligence: Insights from image classification

Explainable AI (XAI) methods provide explanations of AI models, but our understanding of how they compare with human explanations remains limited. Here, we examined human participants' attention strategies when classifying images and when explaining how they classified the images through eye-tracking and compared their attention strategies with saliency-based explanations from current XAI methods. We found that humans adopted more explorative attention strategies for the explanation task than the classification task itself. Two representative explanation strategies were identified through clustering: One involved focused visual scanning on foreground objects with more conceptual explanations, which contained more specific information for inferring class labels, whereas the other involved explorative scanning with more visual explanations, which were rated higher in effectiveness for early category learning. Interestingly, XAI saliency map explanations had the highest similarity to the explorative attention strategy in humans, and explanations highlighting discriminative features from invoking observable causality through perturbation had higher similarity to human strategies than those highlighting internal features associated with higher class score. Thus, humans use both visual and conceptual information during explanation, which serve different purposes, and XAI methods that highlight features informing observable causality match better with human explanations, potentially more accessible to users.

Individual differences in face salience and rapid face saccades

Humans saccade to faces in their periphery faster than to other types of objects. Previous research has highlighted the potential importance of the upper face region in this phenomenon, but it remains unclear whether this is driven by the eye region. Similarly, it remains unclear whether such rapid saccades are exclusive to faces or generalize to other semantically salient stimuli. Furthermore, it is unknown whether individuals differ in their face-specific saccadic reaction times and, if so, whether such differences could be linked to differences in face fixations during free viewing. To explore these open questions, we invited 77 participants to perform a saccadic choice task in which we contrasted faces as well as other salient objects, particularly isolated face features and text, with cars. Additionally, participants freely viewed 700 images of complex natural scenes in a separate session, which allowed us to determine the individual proportion of first fixations falling on faces. For the saccadic choice task, we found advantages for all categories of interest over cars. However, this effect was most pronounced for images of full faces. Full faces also elicited faster saccades compared with eyes, showing that isolated eye regions are not sufficient to elicit face-like responses. Additionally, we found consistent individual differences in saccadic reaction times toward faces that weakly correlated with face salience during free viewing. Our results suggest a link between semantic salience and rapid detection, but underscore the unique status of faces. Further research is needed to resolve the mechanisms underlying rapid face saccades.

The center of a face catches the eye in face perception

Using the "Don't look" (DL) paradigm, wherein participants are asked not to look at a specific feature (i.e., eye, nose, and mouth), we previously documented that Easterners struggled to completely avoid fixating on the eyes and nose. Their underlying mechanisms for attractiveness may differ because the fixations on the eyes were triggered only reflexively, whereas fixations on the nose were consistently elicited. In this study, we predominantly focused on the nose, where the center-of-gravity (CoG) effect, which refers to a person's tendency to look near an object's CoG, could be confounded. Full-frontal and mid-profile faces were used because the latter's CoG did not correspond to the nose location. Although we hypothesized that these two effects are independent, the results indicated that, in addition to the successful tracing of previous studies, the CoG effect explains the nose-attracting effect. This study not only reveals this explanation but also raises a question regarding the CoG effect on Eastern participants.

A preference to look closer to the eyes is associated with a position-invariant face neural code

When looking at faces, humans invariably move their eyes to a consistent preferred first fixation location on the face. While most people have the preferred fixation location just below the eyes, a minority have it between the nose-tip and mouth. Not much is known about whether these long-term differences in the preferred fixation location are associated with distinct neural representations of faces. To study this, we used a gaze-contingent face adaptation aftereffect paradigm to test in two groups of observers, one with their mean preferred fixation location closer to the eyes (upper lookers) and the other closer to the mouth (lower lookers). In this task, participants were required to maintain their gaze at either their own group's mean preferred fixation location or that of the other group during adaptation and testing. The two possible fixation locations were 3.6° apart on the face. We measured the face adaptation aftereffects when the adaptation and testing happened while participants maintained fixation at either the same or different locations on the face. Both groups showed equally strong adaptation effects when the adaptation and testing happened at the same fixation location. Crucially, only the upper lookers showed a partial transfer of the FAE across the two fixation locations, when adaptation occurred at the eyes. Lower lookers showed no spatial transfer of the FAE irrespective of the adaptation position. Given the classic finding that neural tuning is increasingly position invariant as one moves higher in the visual hierarchy, this result suggests that differences in the preferred fixation location are associated with distinct neural representations of faces.

Common structure of saccades and microsaccades in visual perception

We obtain large amounts of external information through our eyes, a process often considered analogous to picture mapping onto a camera lens. However, our eyes are never as still as a camera lens, with saccades occurring between fixations and microsaccades occurring within a fixation. Although saccades are agreed to be functional for information sampling in visual perception, it remains unknown if microsaccades have a similar function when eye movement is restricted. Here, we demonstrated that saccades and microsaccades share common spatiotemporal structures in viewing visual objects. Twenty-seven adults viewed faces and houses in free-viewing and fixation-controlled conditions. Both saccades and microsaccades showed distinctive spatiotemporal patterns between face and house viewing that could be discriminated by pattern classifications. The classifications based on saccades and microsaccades could also be mutually generalized. Importantly, individuals who showed more distinctive saccadic patterns between faces and houses also showed more distinctive microsaccadic patterns. Moreover, saccades and microsaccades showed a higher structure similarity for face viewing than house viewing and a common orienting preference for the eye region over the mouth region. These findings suggested a common oculomotor program that is used to optimize information sampling during visual object perception.

Individual differences in human gaze behavior generalize from faces to objects

Individuals differ in where they fixate on a face, with some looking closer to the eyes while others prefer the mouth region. These individual biases are highly robust, generalize from the lab to the outside world, and have been associated with social cognition and associated disorders. However, it is unclear, whether these biases are specific to faces or influenced by domain-general mechanisms of vision. Here, we juxtaposed these hypotheses by testing whether individual face fixation biases generalize to inanimate objects. We analyzed >1.8 million fixations toward faces and objects in complex natural scenes from 405 participants tested in multiple labs. Consistent interindividual differences in fixation positions were highly inter-correlated across faces and objects in all samples. Observers who fixated closer to the eye region also fixated higher on inanimate objects and vice versa. Furthermore, the inter-individual spread of fixation positions scaled with target size in precisely the same, non-linear manner for faces and objects. These findings contradict a purely domain-specific account of individual face gaze. Instead, they suggest significant domain-general contributions to the individual way we look at faces, a finding with potential relevance for basic vision, face perception, social cognition, and associated clinical conditions.

Differences in eye movements for face recognition between Canadian and Chinese participants are not modulated by social orientation

Face recognition strategies do not generalize across individuals. Many studies have reported robust cultural differences between West Europeans/North Americans and East Asians in eye movement strategies during face recognition. The social orientation hypothesis posits that individualistic vs. collectivistic (IND/COL) value systems, respectively defining West European/North American and East Asian societies, would be at the root of many cultural differences in visual perception. Whether social orientation is also responsible for such cultural contrast in face recognition remains to be clarified. To this aim, we conducted two experiments with West European/North American and Chinese observers. In Experiment 1, we probed the existence of a link between IND/COL social values and eye movements during face recognition, by using an IND/COL priming paradigm. In Experiment 2, we dissected the latter relationship in greater depth, by using two IND/COL questionnaires, including subdimensions to those concepts. In both studies, cultural differences in fixation patterns were revealed between West European/North American and East Asian observers. Priming IND/COL values did not modulate eye movement visual sampling strategies, and only specific subdimensions of the IND/COL questionnaires were associated with distinct eye-movement patterns. Altogether, we show that the typical contrast between IND/COL cannot fully account for cultural differences in eye movement strategies for face recognition. Cultural differences in eye movements for faces might originate from mechanisms distinct from social orientation.

Face detection based on a human attention guided multi-scale model

Multiscale models are among the cutting-edge technologies used for face detection and recognition. An example is Deformable part-based models (DPMs), which encode a face as a multiplicity of local areas (parts) at different resolution scales and their hierarchical and spatial relationship. Although these models have proven successful and incredibly efficient in practical applications, the mutual position and spatial resolution of the parts involved are arbitrarily defined by a human specialist and the final choice of the optimal scales and parts is based on heuristics. This work seeks to understand whether a multi-scale model can take inspiration from human fixations to select specific areas and spatial scales. In more detail, it shows that a multi-scale pyramid representation can be adopted to extract interesting points, and that human attention can be used to select the points at the scales that lead to the best face detection performance. Human fixations can therefore provide a valid methodological basis on which to build a multiscale model, by selecting the spatial scales and areas of interest that are most relevant to humans.

Stable eye versus mouth preference in a live speech-processing task

Looking at the mouth region is thought to be a useful strategy for speech-perception tasks. The tendency to look at the eyes versus the mouth of another person during speech processing has thus far mainly been studied using screen-based paradigms. In this study, we estimated the eye-mouth-index (EMI) of 38 adult participants in a live setting. Participants were seated across the table from an experimenter, who read sentences out loud for the participant to remember in both a familiar (English) and unfamiliar (Finnish) language. No statistically significant difference in the EMI between the familiar and the unfamiliar languages was observed. Total relative looking time at the mouth also did not predict the number of correctly identified sentences. Instead, we found that the EMI was higher during an instruction phase than during the speech-processing task. Moreover, we observed high intra-individual correlations in the EMI across the languages and different phases of the experiment. We conclude that there are stable individual differences in looking at the eyes versus the mouth of another person. Furthermore, this behavior appears to be flexible and dependent on the requirements of the situation (speech processing or not).

Polar angle asymmetries in visual perception and neural architecture

Human visual performance changes with visual field location. It is best at the center of gaze and declines with eccentricity, and also varies markedly with polar angle. These perceptual polar angle asymmetries are linked to asymmetries in the organization of the visual system. We review and integrate research quantifying how performance changes with visual field location and how this relates to neural organization at multiple stages of the visual system. We first briefly review how performance varies with eccentricity and the neural foundations of this effect. We then focus on perceptual polar angle asymmetries and their neural foundations. Characterizing perceptual and neural variations across and around the visual field contributes to our understanding of how the brain translates visual signals into neural representations which form the basis of visual perception.

Where on the face do we look during phonemic restoration: An eye-tracking study

Face to face communication typically involves audio and visual components to the speech signal. To examine the effect of task demands on gaze patterns in response to a speaking face, adults participated in two eye-tracking experiments with an audiovisual (articulatory information from the mouth was visible) and a pixelated condition (articulatory information was not visible). Further, task demands were manipulated by having listeners respond in a passive (no response) or an active (button press response) context. The active experiment required participants to discriminate between speech stimuli and was designed to mimic environmental situations which require one to use visual information to disambiguate the speaker's message, simulating different listening conditions in real-world settings. Stimuli included a clear exemplar of the syllable /ba/ and a second exemplar in which the formant initial consonant was reduced creating an /a/-like consonant. Consistent with our hypothesis, results revealed that the greatest fixations to the mouth were present in the audiovisual active experiment and visual articulatory information led to a phonemic restoration effect for the /a/ speech token. In the pixelated condition, participants fixated on the eyes, and discrimination of the deviant token within the active experiment was significantly greater than the audiovisual condition. These results suggest that when required to disambiguate changes in speech, adults may look to the mouth for additional cues to support processing when it is available.

Cortical magnification eliminates differences in contrast sensitivity across but not around the visual field

Human visual performance changes dramatically both across (eccentricity) and around (polar angle) the visual field. Performance is better at the fovea, decreases with eccentricity, and is better along the horizontal than vertical meridian and along the lower than the upper vertical meridian. However, all neurophysiological and virtually all behavioral studies of cortical magnification have investigated eccentricity effects without considering polar angle. Most performance differences due to eccentricity are eliminated when stimulus size is cortically magnified (M-scaled) to equate the size of its cortical representation in primary visual cortex (V1). But does cortical magnification underlie performance differences around the visual field? Here, to assess contrast sensitivity, human adult observers performed an orientation discrimination task with constant stimulus size at different locations as well as when stimulus size was M-scaled according to stimulus eccentricity and polar angle location. We found that although M-scaling stimulus size eliminates differences across eccentricity, it does not eliminate differences around the polar angle. This finding indicates that limits in contrast sensitivity across eccentricity and around polar angle of the visual field are mediated by different anatomical and computational constraints.

Rational information search in welfare-tradeoff cognition

One of the most important dimensions along which we evaluate others is their propensity to value our welfare: we like people who are disposed to incur costs for our benefit and who refrain from imposing costs on us to benefit themselves. The evolutionary importance of social valuation in our species suggests that humans have cognitive mechanisms that are able to efficiently extract information about how much another person values them. Here I test the hypothesis that people are spontaneously interested in the kinds of events that have the most potential to reveal such information. In two studies, I presented participants (Ns = 216; 300) with pairs of dilemmas that another individual faced in an economic game; for each pair, I asked them to choose the dilemma for which they would most like to see the decision that the individual had made. On average, people spontaneously selected the choices that had the potential to reveal the most information about the individual's valuation of the participant, as quantified by a Bayesian ideal search model. This finding suggests that human cooperation is supported by sophisticated cognitive mechanisms for information-gathering.

Quick, eyes! Isolated upper face regions but not artificial features elicit rapid saccades

Human faces elicit faster saccades than objects or animals, resonating with the great importance of faces for our species. The underlying mechanisms are largely unclear. Here, we test two hypotheses based on previous findings. First, ultra-rapid saccades toward faces may not depend on the presence of the whole face, but the upper face region containing the eye region. Second, ultra-rapid saccades toward faces (and possibly face parts) may emerge from our extensive experience with this stimulus and thus extend to glasses and masks - artificial features frequently encountered as part of a face. To test these hypotheses, we asked 43 participants to complete a saccadic choice task, which contrasted images of whole, upper and lower faces, face masks, and glasses with car images. The resulting data confirmed ultra-rapid saccades for isolated upper face regions, but not for artificial facial features.

Preference for horizontal information in faces predicts typical variations in face recognition but is not impaired in developmental prosopagnosia

Face recognition is strongly influenced by the processing of orientation structure in the face image. Faces are much easier to recognize when they are filtered to include only horizontally oriented information compared with vertically oriented information. Here, we investigate whether preferences for horizontal information in faces are related to face recognition abilities in a typical sample (Experiment 1), and whether such preferences are lacking in people with developmental prosopagnosia (DP; Experiment 2). Experiment 1 shows that preferences for horizontal face information are linked to face recognition abilities in a typical sample, with weak evidence of face-selective contributions. Experiment 2 shows that preferences for horizontal face information are comparable in control and DP groups. Our study suggests that preferences for horizontal face information are related to variations in face recognition abilities in the typical range, and that these preferences are not aberrant in DP.

Stimulus size modulates idiosyncratic neural face identity discrimination

Humans show individual differences in neural facial identity discrimination (FID) responses across viewing positions. Critically, these variations have been shown to be reliable over time and to directly relate to observers' idiosyncratic preferences in facial information sampling. This functional signature in facial identity processing might relate to observer-specific diagnostic information processing. Although these individual differences are a valuable source of information for interpreting data, they can also be difficult to isolate when it is not possible to test many conditions. To address this potential issue, we explored whether reducing stimulus size would help decrease these interindividual variations in neural FID. We manipulated the size of face stimuli (covering 3°, 5°, 6.7°, 8.5°, and 12° of visual angle), as well as the fixation location (left eye, right eye, below the nasion, nose, and mouth) while recording electrophysiological responses. Same identity faces were presented with a base frequency of 6 Hz. Different identity faces were periodically inserted within this sequence to trigger an objective index of neural FID. Our data show robust and consistent individual differences in neural face identity discrimination across viewing positions for all face sizes. Nevertheless, FID was optimal for a larger number of observers when faces subtended 6.7° of visual angle and fixation was below the nasion. This condition is the most suited to reduce natural interindividual variations in neural FID patterns, defining an important benchmark to measure neural FID when it is not possible to assess and control for observers' idiosyncrasies.

The Eyes Have It: Psychotherapy in the Era of Masks

Nonverbal communication is integral to the success of psychotherapy and facial expression is an important component of nonverbal communication. The SARS CoV-2 pandemic has caused alterations in how psychotherapy services are provided. In this paper, potential issues that may arise from conducting psychotherapy when both the patient and therapist are wearing masks are explored. These include higher likelihood of misidentifying facial expression, especially when expression is incongruent with body language, and when the lower face is more important for correct identification of emotion. These issues may be particularly problematic for patient populations for whom emotion recognition may be a problem at baseline, or for those more prone to biases in emotional recognition. Suggestions are made for therapists to consider when seeing patients in-person when masks are necessary.

Individual fixation tendencies in person viewing generalize from images to videos

Fixation behavior toward persons in static scenes varies considerably between individuals. However, it is unclear whether these differences generalize to dynamic stimuli. Here, we examined individual differences in the distribution of gaze across seven person features (i.e. body and face parts) in static and dynamic scenes. Forty-four participants freely viewed 700 complex static scenes followed by eight director-cut videos (28,925 frames). We determined the presence of person features using hand-delineated pixel masks (images) and Deep Neural Networks (videos). Results replicated highly consistent individual differences in fixation tendencies for all person features in static scenes and revealed that these tendencies generalize to videos. Individual fixation behavior for both, images and videos, fell into two anticorrelated clusters representing the tendency to fixate faces versus bodies. These results corroborate a low-dimensional space for individual gaze biases toward persons and show they generalize from images to videos.

Individual differences in looking at persons in scenes

Individuals freely viewing complex scenes vary in their fixation behavior. The most prominent and reliable dimension of such individual differences is the tendency to fixate faces. However, much less is known about how observers distribute fixations across other body parts of persons in scenes and how individuals may vary in this regard. Here, we aimed to close this gap. We expanded a popular annotated stimulus set (Xu, Jiang, Wang, Kankanhalli, & Zhao, 2014) with 6,365 hand-delineated pixel masks for the body parts of 1,136 persons embedded in 700 complex scenes, which we publish with this article (https://osf.io/ynujz/). This resource allowed us to analyze the person-directed fixations of 103 participants freely viewing these scenes. We found large and reliable individual differences in the distribution of fixations across person features. Individual fixation tendencies formed two anticorrelated clusters, one for the eyes, head, and the inner face and one for body features (torsi, arms, legs, and hands). Interestingly, the tendency to fixate mouths was independent of the face cluster. Finally, our results show that observers who tend to avoid person fixations in general, particularly do so for the face region. These findings underscore the role of individual differences in fixation behavior and reveal underlying dimensions. They are further in line with a recently proposed push-pull relationship between cortical tuning for faces and bodies. They may also aid the comparison of special populations to general variation.

Understanding the role of eye movement consistency in face recognition and autism through integrating deep neural networks and hidden Markov models

Greater eyes-focused eye movement pattern during face recognition is associated with better performance in adults but not in children. We test the hypothesis that higher eye movement consistency across trials, instead of a greater eyes-focused pattern, predicts better performance in children since it reflects capacity in developing visual routines. We first simulated visual routine development through combining deep neural network and hidden Markov model that jointly learn perceptual representations and eye movement strategies for face recognition. The model accounted for the advantage of eyes-focused pattern in adults, and predicted that in children (partially trained models) consistency but not pattern of eye movements predicted recognition performance. This result was then verified with data from typically developing children. In addition, lower eye movement consistency in children was associated with autism diagnosis, particularly autistic traits in social skills. Thus, children's face recognition involves visual routine development through social exposure, indexed by eye movement consistency.

Characteristic fixation biases in Super-Recognizers

Neurotypical observers show large and reliable individual differences in gaze behavior along several semantic object dimensions. Individual gaze behavior toward faces has been linked to face identity processing, including that of neurotypical observers. Here, we investigated potential gaze biases in Super-Recognizers (SRs), individuals with exceptional face identity processing skills. Ten SRs, identified with a novel conservative diagnostic framework, and 43 controls freely viewed 700 complex scenes depicting more than 5000 objects. First, we tested whether SRs and controls differ in fixation biases along four semantic dimensions: faces, text, objects being touched, and bodies. Second, we tested potential group differences in fixation biases toward eyes and mouths. Finally, we tested whether SRs fixate closer to the theoretical optimal fixation point for face identification. SRs showed a stronger gaze bias toward faces and away from text and touched objects, starting from the first fixation onward. Further, SRs spent a significantly smaller proportion of first fixations and dwell time toward faces on mouths but did not differ in dwell time or first fixations devoted to eyes. Face fixation of SRs also fell significantly closer to the theoretical optimal fixation point for identification, just below the eyes. Our findings suggest that reliable superiority for face identity processing is accompanied by early fixation biases toward faces and preferred saccadic landing positions close to the theoretical optimum for face identification. We discuss future directions to investigate the functional basis of individual fixation behavior and face identity processing ability.

Impact of mask use on face recognition: an eye-tracking study

We examined how mask use affects performance and eye movements in face recognition and whether strategy change reflected in eye movements is associated with performance change. Eighty-eight participants performed face recognition with masked faces either during learning only, during recognition only, or during both learning and recognition. As compared with the baseline condition where faces were unmasked during both learning and recognition, participants had impaired performance in all three scenarios, with larger impairment when mask conditions during learning and recognition did not match. When recognizing unmasked faces, whether the faces were learned with or without a mask on did not change eye movement behavior. Nevertheless, when recognizing unmasked faces that were learned with a mask on, participants who adopted more eyes-focused patterns had less performance impairment as compared with the baseline condition. When recognizing masked faces, participants had more eyes-focused patterns and more consistent gaze transition behavior than recognizing unmasked faces regardless of whether the faces were learned with or without a mask on. Nevertheless, when recognizing masked faces that were learned without a mask, participants whose gaze transition behavior was more consistent had less performance impairment as compared with the baseline condition. Thus, although eye movements during recognition were mainly driven by the mask condition during recognition but not that during learning, those who adjusted their strategy according to the mask condition difference between learning and recognition had better performance. This finding has important implications for identifying populations vulnerable to the impact of mask use and potential remedial strategies.

Face masks versus sunglasses: limited effects of time and individual differences in the ability to judge facial identity and social traits

Some research indicates that face masks impair identification and other judgements such as trustworthiness. However, it is unclear whether those effects have abated over time as individuals adjust to widespread use of masks, or whether performance is related to individual differences in face recognition ability. This study examined the effect of masks and sunglasses on face matching and social judgements (trustworthiness, competence, attractiveness). In Experiment 1, 135 participants across three different time points (June 2020-July 2021) viewed unedited faces and faces with masks, sunglasses, or both. Both masks and sunglasses similarly decreased matching performance. The effect of masks on social judgements varied depending on the judgement and whether the face was depicted with sunglasses. There was no effect of timepoint on any measure, suggesting that the effects of masks have not diminished. In Experiment 2, 12 individuals with developmental prosopagnosia (DP) and 10 super-recognisers (SRs) completed the same tasks. The effect of masks on identity matching was reduced in SRs, whereas the effects of masks and sunglasses for the DP group did not differ from controls. These findings indicate that face masks significantly affect face perception, depending on the availability of other facial information, and are not modified by exposure.

EXPRESS: Distinct abilities associated with matching same identity faces vs. discriminating different faces: Evidence from individual differences in prosopagnosics and controls

Previous face matching studies provide evidence that matching same identity faces (match trials) and discriminating different face identities (non-match trials) rely on distinct processes. For example, instructional studies geared towards improving face matching in applied settings have often found selective improvements in match or non-match trials only. Additionally, a small study found that developmental prosopagnosics (DPs) have specific deficits in making match but not non-match judgments. In the current study, we sought to replicate this finding in DPs and examine how individual differences across DPs and controls in match vs. non-match performance relate to featural vs. holistic processing abilities. 43 DPs and 27 controls matched face images shown from similar front views or with varied lighting or viewpoint. Participants also performed tasks measuring featural (eyes/mouth) and holistic processing (part-whole task). We found that DPs showed worse overall matching performance than controls and that their relative match vs. non-match deficit depended on image variation condition, indicating that DPs do not consistently show match- or non-match-specific deficits. When examining the association between holistic and featural processing abilities and match vs. non-match trials in the entire group of DPs and controls, we found a very clear dissociation: Match trials significantly correlated with eye processing ability (r=.48) but not holistic processing (r=.11), whereas non-match trials significantly correlated with holistic processing (r=.32) but not eye processing (r=.03). This suggests that matching same identity faces relies more on eye processing while discriminating different faces relies more on holistic processing.

Foveal processing of emotion-informative facial features

Certain facial features provide useful information for recognition of facial expressions. In two experiments, we investigated whether foveating informative features of briefly presented expressions improves recognition accuracy and whether these features are targeted reflexively when not foveated. Angry, fearful, surprised, and sad or disgusted expressions were presented briefly at locations which would ensure foveation of specific features. Foveating the mouth of fearful, surprised and disgusted expressions improved emotion recognition compared to foveating an eye or cheek or the central brow. Foveating the brow led to equivocal results in anger recognition across the two experiments, which might be due to the different combination of emotions used. There was no consistent evidence suggesting that reflexive first saccades targeted emotion-relevant features; instead, they targeted the closest feature to initial fixation. In a third experiment, angry, fearful, surprised and disgusted expressions were presented for 5 seconds. Duration of task-related fixations in the eyes, brow, nose and mouth regions was modulated by the presented expression. Moreover, longer fixation at the mouth positively correlated with anger and disgust accuracy both when these expressions were freely viewed (Experiment 2b) and when briefly presented at the mouth (Experiment 2a). Finally, an overall preference to fixate the mouth across all expressions correlated positively with anger and disgust accuracy. These findings suggest that foveal processing of informative features is functional/contributory to emotion recognition, but they are not automatically sought out when not foveated, and that facial emotion recognition performance is related to idiosyncratic gaze behaviour.

Gaze and speech behavior in parent–child interactions: The role of conflict and cooperation

A primary mode of human social behavior is face-to-face interaction. In this study, we investigated the characteristics of gaze and its relation to speech behavior during video-mediated face-to-face interactions between parents and their preadolescent children. 81 parent–child dyads engaged in conversations about cooperative and conflictive family topics. We used a dual-eye tracking setup that is capable of concurrently recording eye movements, frontal video, and audio from two conversational partners. Our results show that children spoke more in the cooperation-scenario whereas parents spoke more in the conflict-scenario. Parents gazed slightly more at the eyes of their children in the conflict-scenario compared to the cooperation-scenario. Both parents and children looked more at the other's mouth region while listening compared to while speaking. Results are discussed in terms of the role that parents and children take during cooperative and conflictive interactions and how gaze behavior may support and coordinate such interactions.

Effects of Self-Esteem on Self-Viewing: An Eye-Tracking Investigation on Mirror Gazing

While some people enjoy looking at their faces in the mirror, others experience emotional distress. Despite these individual differences concerning self-viewing in the mirror, systematic investigations on this topic have not been conducted so far. The present eye-tracking study examined whether personality traits (self-esteem, narcissism propensity, self-disgust) are associated with gaze behavior (gaze duration, fixation count) during free mirror viewing of one's face. Sixty-eight adults (mean age = 23.5 years; 39 females, 29 males) viewed their faces in the mirror and watched a video of an unknown person matched for gender and age (control condition) for 90 s each. The computed regression analysis showed that higher self-esteem was associated with a shorter gaze duration for both self-face and other-face. This effect may reflect a less critical evaluation of the faces.

Peripheral facial features guiding eye movements and reducing fixational variability

Face processing is a fast and efficient process due to its evolutionary and social importance. A majority of people direct their first eye movement to a featureless point just below the eyes that maximizes accuracy in recognizing a person's identity and gender. Yet, the exact properties or features of the face that guide the first eye movements and reduce fixational variability are unknown. Here, we manipulated the presence of the facial features and the spatial configuration of features to investigate their effect on the location and variability of first and second fixations to peripherally presented faces. Our results showed that observers can utilize the face outline, individual facial features, and feature spatial configuration to guide the first eye movements to their preferred point of fixation. The eyes have a preferential role in guiding the first eye movements and reducing fixation variability. Eliminating the eyes or altering their position had the greatest influence on the location and variability of fixations and resulted in the largest detriment to face identification performance. The other internal features (nose and mouth) also contribute to reducing fixation variability. A subsequent experiment measuring detection of single features showed that the eyes have the highest detectability (relative to other features) in the visual periphery providing a strong sensory signal to guide the oculomotor system. Together, the results suggest a flexible multiple-cue approach that might be a robust solution to cope with how the varying eccentricities in the real world influence the ability to resolve individual feature properties and the preferential role of the eyes.

Average faces: How does the averaging process change faces physically and perceptually?

Average faces have been used frequently in face recognition studies, either as a theoretical concept (e.g., face norm) or as a tool to manipulate facial attributes (e.g., modifying identity strength). Nonetheless, how the face averaging process- the creation of average faces using an increasing number of faces -changes the resulting averaged faces and our ability to differentiate between them remains to be elucidated. Here we addressed these questions by combining 3D-face averaging, eye-movement tracking, and the computation of image-based face similarity. Participants judged whether two average faces showed the same person while we systematically increased their average level (i.e., number of faces being averaged). Our results showed, with increasing averaging, both a nonlinear increase of the computational similarity between the resulting average faces and a nonlinear decrease of face discrimination performance. Participants' performance dropped from near-ceiling level when two different faces had been averaged together to chance level when 80 faces were mixed. We also found a nonlinear relationship between face similarity and face discrimination performance, which was fitted nicely with an exponential function. Furthermore, when the comparison task became more challenging, participants performed more fixations onto the faces. Nonetheless, the distribution of fixations across facial features (eyes, nose, mouth, and the center area of a face) remained unchanged. These results not only set new constraints on the theoretical characterization of the average face and its role in establishing face norms but also offer practical guidance for creating approximated face norms to manipulate face identity.

Assessing Gender-Affirming Chest Surgery Outcomes: Does Gender Identity Alter Gaze?

BACKGROUND

Outcomes of gender-affirming chest surgery can be variable. Placement of nipple-areolar complexes and orientation of scars can drastically affect the aesthetic outcomes of these procedures, as may observer gender identity. Here, we compared attention and perception of outcomes following gender-affirming chest surgery between laypersons, based on gender identity.

METHODS

Transgender and cisgender participants were enrolled and shown images of surgery naïve chests and postoperative masculinized and feminized chests, blinded to the gender identity of the photographed subject. Gaze data were captured using the Tobii X2 60 eye-tracking device. Participants scored the perceived gender and aesthetic appearance of each image.

RESULTS

Eighteen cisgender and 14 transgender participants were enrolled. When viewing male chests, transgender participants spent significantly longer fixated on the nipples (naïve: 802 vs. 395 ms; p = 0.02, masculinized: 940 vs. 692 ms, p = 0.002). For masculinized chests, cisgender participants spent significantly longer fixated on the inframammary scar (483 vs. 391 ms; p = 0.04). On images of feminized chests, transgender participants spent longer viewing the nipples when compared to cisgender participants (1017 vs. 847 ms; p = 0.04). Cisgender viewers spent longer fixating on the postoperative scar on feminized chests (113 vs. 59 ms; p = 0.02) and also viewed feminized chests as significantly more masculine and masculinized chests as more feminine, when compared to transgender participants (p < 0.05).

CONCLUSIONS

This is the first study to use eye-tracking to assess how laypersons assess chests for gender determination. The findings suggest that observer gender identity has an effect on areas of focus and gender perception of chests that underwent gender-affirmation surgery.

LEVEL OF EVIDENCE III

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine Ratings, please refer to Table of Contents or online Instructions to Authors www.springer.com/00266 .

Varying Stimulus Duration Reveals Consistent Neural Activity and Behavior for Human Face Individuation

Establishing consistent relationships between neural activity and behavior is a challenge in human cognitive neuroscience research. We addressed this issue using variable time constraints in an oddball frequency-sweep design for visual discrimination of complex images (face exemplars). Sixteen participants viewed sequences of ascending presentation durations, from 25 to 333 ms (40-3 Hz stimulation rate) while their electroencephalogram (EEG) was recorded. Throughout each sequence, the same unfamiliar face picture was repeated with variable size and luminance changes while different unfamiliar facial identities appeared every 1 s (1 Hz). A neural face individuation response, tagged at 1 Hz and its unique harmonics, emerged over the occipito-temporal cortex at 50 ms stimulus duration (25-100 ms across individuals), with an optimal response reached at 170 ms stimulus duration. In a subsequent experiment, identity changes appeared non-periodically within fixed-frequency sequences while the same participants performed an explicit face individuation task. The behavioral face individuation response also emerged at 50 ms presentation time, and behavioral accuracy correlated with individual participants' neural response amplitude in a weighted middle stimulus duration range (50-125 ms). Moreover, the latency of the neural response peaking between 180 and 200 ms correlated strongly with individuals' behavioral accuracy in this middle duration range, as measured independently. These observations point to the minimal (50 ms) and optimal (170 ms) stimulus durations for human face individuation and provide novel evidence that inter-individual differences in the magnitude and latency of early, high-level neural responses are predictive of behavioral differences in performance at this function.

Inferior Occipital Gyrus Is Organized along Common Gradients of Spatial and Face-Part Selectivity

The ventral visual stream of the human brain is subdivided into patches with categorical stimulus preferences, like faces or scenes. However, the functional organization within these areas is less clear. Here, we used functional magnetic resonance imaging and vertex-wise tuning models to independently probe spatial and face-part preferences in the inferior occipital gyrus (IOG) of healthy adult males and females. The majority of responses were well explained by Gaussian population tuning curves for both retinotopic location and the preferred relative position within a face. Parameter maps revealed a common gradient of spatial and face-part selectivity, with the width of tuning curves drastically increasing from posterior to anterior IOG. Tuning peaks clustered more idiosyncratically but were also correlated across maps of visual and face space. Preferences for the upper visual field went along with significantly increased coverage of the upper half of the face, matching recently discovered biases in human perception. Our findings reveal a broad range of neural face-part selectivity in IOG, ranging from narrow to "holistic." IOG is functionally organized along this gradient, which in turn is correlated with retinotopy.SIGNIFICANCE STATEMENT Brain imaging has revealed a lot about the large-scale organization of the human brain and visual system. For example, occipital cortex contains map-like representations of the visual field, while neurons in ventral areas cluster into patches with categorical preferences, like faces or scenes. Much less is known about the functional organization within these areas. Here, we focused on a well established face-preferring area-the inferior occipital gyrus (IOG). A novel neuroimaging paradigm allowed us to map the retinotopic and face-part tuning of many recording sites in IOG independently. We found a steep posterior-anterior gradient of decreasing face-part selectivity, which correlated with retinotopy. This suggests the functional role of ventral areas is not uniform and may follow retinotopic "protomaps."

Eye movement strategies in face ethnicity categorization vs. face identification tasks

A quick look at a face allows us to identify the person, their gender, and emotion. Humans direct their first eye movement towards points on the face that vary moderately across these common tasks and maximize performance. However, not known is the extent to which humans alter their oculomotor strategies to maximize accuracy in more specialized face categorization tasks. We studied the eye movements of Indian observers during a North vs. South Indian face categorization task and compared them to those in a person-identification task. We found that observers did not alter their first eye movement strategy for the ethnic categorization task, i.e., they directed their first fixations to a similar preferred point as in the person-identification task. To assess whether using a similar preferred point of fixation for both tasks resulted in a performance cost for the categorization task, we measured performance as a function of fixation position along the face. Fixating away from the preferred point of fixation reduced observer performance in the person identification task, but not in the ethnicity categorization task. We used computational modeling to assess whether the results could be explained by an interaction between the distribution of task information across the face and the foveated properties of the visual system. A foveated ideal observer analysis revealed a spatially more distributed task information and lower dependence of performance on the point of fixation for the ethnicity categorization task relative to the person identification. We conclude that, unlike the person identification task, humans can access the information for the ethnicity categorization task from various points of fixation. Thus, the observer strategy to utilize the typical person identification first eye movement for the ethnicity categorization task is a simple solution that incurs little or no performance cost.

Gauging facial feature viewing preference as a stable individual trait in autism spectrum disorder

Eye tracking provides insights into social processing deficits in autism spectrum disorder (ASD), especially in conjunction with dynamic, naturalistic free-viewing stimuli. However, the question remains whether gaze characteristics, such as preference for specific facial features, can be considered a stable individual trait, particularly in those with ASD. If so, how much data are needed for consistent estimations? To address these questions, we assessed the stability and robustness of gaze preference for facial features as incremental amounts of movie data were introduced for analysis. We trained an artificial neural network to create an object-based segmentation of naturalistic movie clips (14 s each, 7410 frames total). Thirty-three high-functioning individuals with ASD and 36 age- and IQ-equated typically developing individuals (age range: 12-30 years) viewed 22 Hollywood movie clips, each depicting a social interaction. As we evaluated combinations of one, three, five, eight, and 11 movie clips, gaze dwell times on core facial features became increasingly stable at within-subject, within-group, and between-group levels. Using a number of movie clips deemed sufficient by our analysis, we found that individuals with ASD displayed significantly less face-centered gaze (centralized on the nose; p < 0.001) but did not significantly differ from typically developing participants in eye or mouth looking times. Our findings validate gaze preference for specific facial features as a stable individual trait and highlight the possibility of misinterpretation with insufficient data. Additionally, we propose the use of a machine learning approach to stimuli segmentation to quickly and flexibly prepare dynamic stimuli for analysis. LAY SUMMARY: Using a data-driven approach to segmenting movie stimuli, we examined varying amounts of data to assess the stability of social gaze in individuals with autism spectrum disorder (ASD). We found a reduction in social fixations in participants with ASD, driven by decreased attention to the center of the face. Our findings further support the validity of gaze preference for face features as a stable individual trait when sufficient data are used.

Cultural Differences in Face Recognition and Potential Underlying Mechanisms

The ability to recognize a face is crucial for the success of social interactions. Understanding the visual processes underlying this ability has been the focus of a long tradition of research. Recent advances in the field have revealed that individuals having different cultural backgrounds differ in the type of visual information they use for face processing. However, the mechanisms that underpin these differences remain unknown. Here, we revisit recent findings highlighting group differences in face processing. Then, we integrate these results in a model of visual categorization developed in the field of psychophysics: the RAP framework. On the basis of this framework, we discuss potential mechanisms, whether face-specific or not, that may underlie cross-cultural differences in face perception.

Eye movement analysis with hidden Markov models (EMHMM) with co-clustering

The eye movement analysis with hidden Markov models (EMHMM) method provides quantitative measures of individual differences in eye-movement pattern. However, it is limited to tasks where stimuli have the same feature layout (e.g., faces). Here we proposed to combine EMHMM with the data mining technique co-clustering to discover participant groups with consistent eye-movement patterns across stimuli for tasks involving stimuli with different feature layouts. Through applying this method to eye movements in scene perception, we discovered explorative (switching between the foreground and background information or different regions of interest) and focused (mainly looking at the foreground with less switching) eye-movement patterns among Asian participants. Higher similarity to the explorative pattern predicted better foreground object recognition performance, whereas higher similarity to the focused pattern was associated with better feature integration in the flanker task. These results have important implications for using eye tracking as a window into individual differences in cognitive abilities and styles. Thus, EMHMM with co-clustering provides quantitative assessments on eye-movement patterns across stimuli and tasks. It can be applied to many other real-life visual tasks, making a significant impact on the use of eye tracking to study cognitive behavior across disciplines.