Genetic algorithms reveal profound individual differences in emotion recognition.

Emotional communication relies on a mutual understanding, between expresser and viewer, of facial configurations that broadcast specific emotions. However, we do not know whether people share a common understanding of how emotional states map onto facial expressions. This is because expressions exist in a high-dimensional space too large to explore in conventional experimental paradigms. Here, we address this by adapting genetic algorithms and combining them with photorealistic three-dimensional avatars to efficiently explore the high-dimensional expression space. A total of 336 people used these tools to generate facial expressions that represent happiness, fear, sadness, and anger. We found substantial variability in the expressions generated via our procedure, suggesting that different people associate different facial expressions to the same emotional state. We then examined whether variability in the facial expressions created could account for differences in performance on standard emotion recognition tasks by asking people to categorize different test expressions. We found that emotion categorization performance was explained by the extent to which test expressions matched the expressions generated by each individual. Our findings reveal the breadth of variability in people's representations of facial emotions, even among typical adult populations. This has profound implications for the interpretation of responses to emotional stimuli, which may reflect individual differences in the emotional category people attribute to a particular facial expression, rather than differences in the brain mechanisms that produce emotional responses.

Influence of prior knowledge on eye movements to scenes as revealed by hidden Markov models.

Human visual experience usually provides ample opportunity to accumulate knowledge about events unfolding in the environment. In typical scene perception experiments, however, participants view images that are unrelated to each other and, therefore, they cannot accumulate knowledge relevant to the upcoming visual input. Consequently, the influence of such knowledge on how this input is processed remains underexplored. Here, we investigated this influence in the context of gaze control. We used sequences of static film frames arranged in a way that allowed us to compare eye movements to identical frames between two groups: a group that accumulated prior knowledge relevant to the situations depicted in these frames and a group that did not. We used a machine learning approach based on hidden Markov models fitted to individual scanpaths to demonstrate that the gaze patterns from the two groups differed systematically and, thereby, showed that recently accumulated prior knowledge contributes to gaze control. Next, we leveraged the interpretability of hidden Markov models to characterize these differences. Additionally, we report two unexpected and interesting caveats of our approach. Overall, our results highlight the importance of recently acquired prior knowledge for oculomotor control and the potential of hidden Markov models as a tool for investigating it.

Trust and childhood maltreatment: evidence of bias in appraisal of unfamiliar faces.

BACKGROUND: Child maltreatment is associated with poorer social functioning and increased risk of mental health problems in adolescence and adulthood, but the processes underlying these associations remain unclear. Although crucial for establishing and maintaining relationships, trust judgements have not been experimentally investigated in children who have experienced abuse and neglect. METHODS: A community-based sample of 75 children aged 8-16 years with maltreatment documented on the basis of social services records, and a group of 70 peers matched on age, gender, cognitive ability, socioeconomic status, and ethnicity took part in the study. Children completed a trustworthiness face-judgement task in which they appraised the trustworthiness of unfamiliar facial stimuli varying along a computationally modelled trustworthiness dimension. RESULTS: In line with clinical observations that childhood maltreatment is associated with an atypical pattern of trust processing, children with maltreatment experience were significantly less likely than their peers to rate unfamiliar faces as trustworthy. Moreover, they were more variable in their trust attributions than their peers. CONCLUSIONS: The study provides compelling experimental evidence that children with documented maltreatment perceive others as less trustworthy than their peers and are less consistent in their estimates of trustworthiness in others. Over time, alterations in trust processing may disrupt the development of social bonds and contribute to 'social thinning' (a reduction in the extent and quality of social relationships), leaving children more vulnerable to environmental stressors, increasing risk of mental health difficulties.

War-related trauma linked to increased sustained attention to threat in children.

Experiences of war and displacement can have profound effects on children's affective development and mental health, although the mechanism(s) underlying these effects remain unknown. This study investigated the link between early adversity and attention to affective stimuli using a free-viewing eye-tracking paradigm with Syrian refugee (n = 31, Mage  = 9.55, 12 female) and Jordanian non-refugee (n = 55, Mage  = 9.98, 30 female) children living in Jordan (March 2020). Questionnaires assessed PTSD, anxiety/depression, insecurity, distress, and trauma. Refugee children showed greater initial avoidance of angry and happy faces compared to non-refugee children, and higher trauma exposure was linked to increased sustained attention to angry stimuli. These findings suggest that war-related trauma may have differential effects on the early and later stages of affective processing in refugee children.

Identifying criminals: No biasing effect of criminal context on recalled threat.

To date, it is still unclear whether there is a systematic pattern in the errors made in eyewitness recall and whether certain features of a person are more likely to lead to false identification. Moreover, we also do not know the extent of systematic errors impacting identification of a person from their body rather than solely their face. To address this, based on the contextual model of eyewitness identification (CMEI; Osborne & Davies, 2014, Applied Cognitive Psychology, 28[3], 392-402), we hypothesized that having framed a target as a perpetrator of a violent crime, participants would recall that target person as appearing more like a stereotypical criminal (i.e., more threatening). In three separate experiments, participants were first presented with either no frame, a neutral frame, or a criminal frame (perpetrators of a violent crime) accompanying a target (either a face or body). Participants were then asked to identify the original target from a selection of people that varied in facial threat or body musculature. Contrary to our hypotheses, we found no evidence of bias. However, identification accuracy was highest for the most threatening target bodies high in musculature, as well as bodies paired with detailed neutral contextual information. Overall, these findings suggest that while no systematic bias exists in the recall of criminal bodies, the nature of the body itself and the context in which it is presented can significantly impact identification accuracy.

Promoting well-being in refugee children: An exploratory controlled trial of a positive psychology intervention delivered in Greek refugee camps.

Rigorously evaluated interventions that target protective factors and positive resources rather than ameliorating negative outcomes in child refugees are rare. To address this, we developed and evaluated a short, group-based resilience-building intervention called Strengths for the Journey (SFJ), which was designed for war-affected children. We conducted a quasi-randomized pilot study of the SFJ intervention with 72 7- to 14-year-old forcibly displaced children (Mage = 10.76, 64.8% female) in three refugee camps in Lesvos, Greece. Intervention effectiveness was assessed by measuring pre-post changes in well-being, self-esteem, optimism, and depressive symptoms from before (T1) to immediately after the intervention/wait-list task (T2). Four focus group interviews were conducted with 31 of the participants to discuss their views on the effects of the intervention and the continued use of the skills that were learned. Using repeated-measures ANOVAs, we found improvements in well-being, F (1, 46) = 42.99, ηp2 = .48, self-esteem, F (1, 56) = 29.11, ηp2 = .40, optimism, F (1, 53) = 27.16, ηp2 = .34, and depressive symptoms, F (1, 31) = 62.14, ηp2 = .67, in the intervention group compared with the wait-listed group (p < .05). Focus group participants highlighted the importance of SFJ in developing a sense of togetherness and building their strengths. Child refugees in low-resource settings may benefit from brief, first-line interventions that target protective factors such as well-being, hope, self-esteem, and belonging.

A perceptual bias for man-made objects in humans.

Ambiguous images are widely recognized as a valuable tool for probing human perception. Perceptual biases that arise when people make judgements about ambiguous images reveal their expectations about the environment. While perceptual biases in early visual processing have been well established, their existence in higher-level vision has been explored only for faces, which may be processed differently from other objects. Here we developed a new, highly versatile method of creating ambiguous hybrid images comprising two component objects belonging to distinct categories. We used these hybrids to measure perceptual biases in object classification and found that images of man-made (manufactured) objects dominated those of naturally occurring (non-man-made) ones in hybrids. This dominance generalized to a broad range of object categories, persisted when the horizontal and vertical elements that dominate man-made objects were removed and increased with the real-world size of the manufactured object. Our findings show for the first time that people have perceptual biases to see man-made objects and suggest that extended exposure to manufactured environments in our urban-living participants has changed the way that they see the world.

Semantic content outweighs low-level saliency in determining children's and adults' fixation of movies.

To make sense of the visual world, we need to move our eyes to focus regions of interest on the high-resolution fovea. Eye movements, therefore, give us a way to infer mechanisms of visual processing and attention allocation. Here, we examined age-related differences in visual processing by recording eye movements from 37 children (aged 6-14years) and 10 adults while viewing three 5-min dynamic video clips taken from child-friendly movies. The data were analyzed in two complementary ways: (a) gaze based and (b) content based. First, similarity of scanpaths within and across age groups was examined using three different measures of variance (dispersion, clusters, and distance from center). Second, content-based models of fixation were compared to determine which of these provided the best account of our dynamic data. We found that the variance in eye movements decreased as a function of age, suggesting common attentional orienting. Comparison of the different models revealed that a model that relies on faces generally performed better than the other models tested, even for the youngest age group (<10years). However, the best predictor of a given participant's eye movements was the average of all other participants' eye movements both within the same age group and in different age groups. These findings have implications for understanding how children attend to visual information and highlight similarities in viewing strategies across development.

Personality Traits Do Not Predict How We Look at Faces.

While personality has typically been considered to influence gaze behaviour, literature relating to the topic is mixed. Previously, we found no evidence of self-reported personality traits on preferred gaze duration between a participant and a person looking at them via a video. In this study, 77 of the original participants answered an in-depth follow-up survey containing a more comprehensive assessment of personality traits (Big Five Inventory) than was initially used, to check whether earlier findings were caused by the personality measure being too coarse. In addition to preferred mutual gaze duration, we also examined two other factors linked to personality traits: number of blinks and total fixation duration in the eye region of observed faces. No significant correlations were found between any of these measures and participant personality traits. We suggest that effects previously reported in the literature may stem from contextual differences or modulation of arousal.

Directional Limits on Motion Transparency Assessed Through Colour-Motion Binding.

Motion-defined transparency is the perception of two or more distinct moving surfaces at the same retinal location. We explored the limits of motion transparency using superimposed surfaces of randomly positioned dots defined by differences in motion direction and colour. In one experiment, dots were red or green and we varied the proportion of dots of a single colour that moved in a single direction ('colour-motion coherence') and measured the threshold direction difference for discriminating between two directions. When colour-motion coherences were high (e.g., 90% of red dots moving in one direction), a smaller direction difference was required to correctly bind colour with direction than at low coherences. In another experiment, we varied the direction difference between the surfaces and measured the threshold colour-motion coherence required to discriminate between them. Generally, colour-motion coherence thresholds decreased with increasing direction differences, stabilising at direction differences around 45°. Different stimulus durations were compared, and thresholds were higher at the shortest (150 ms) compared with the longest (1,000 ms) duration. These results highlight different yet interrelated aspects of the task and the fundamental limits of the mechanisms involved: the resolution of narrowly separated directions in motion processing and the local sampling of dot colours from each surface.

Comparing averaging limits for social cues over space and time.

Observers are able to extract summary statistics from groups of faces, such as their mean emotion or identity. This can be done for faces presented simultaneously and also from sequences of faces presented at a fixed location. Equivalent noise analysis, which estimates an observer's internal noise (the uncertainty in judging a single element) and effective sample size (ESS; the effective number of elements being used to judge the average), reveals what limits an observer's averaging performance. It has recently been shown that observers have lower ESSs and higher internal noise for judging the mean gaze direction of a group of spatially distributed faces compared to the mean head direction of the same faces. In this study, we use the equivalent noise technique to compare limits on these two cues to social attention under two presentation conditions: spatially distributed and sequentially presented. We find that the differences in ESS are replicated in spatial arrays but disappear when both cue types are averaged over time, suggesting that limited peripheral gaze perception prevents accurate averaging performance. Correlation analysis across participants revealed generic limits for internal noise that may act across stimulus and presentation types, but no clear shared limits for ESS. This result supports the idea of some shared neural mechanisms b in early stages of visual processing.

Testing the dual-route model of perceived gaze direction: Linear combination of eye and head cues.

We have recently proposed a dual-route model of the effect of head orientation on perceived gaze direction (Otsuka, Mareschal, Calder, & Clifford, 2014; Otsuka, Mareschal, & Clifford, 2015), which computes perceived gaze direction as a linear combination of eye orientation and head orientation. By parametrically manipulating eye orientation and head orientation, we tested the adequacy of a linear model to account for the effect of horizontal head orientation on perceived direction of gaze. Here, participants adjusted an on-screen pointer toward the perceived gaze direction in two image conditions: Normal condition and Wollaston condition. Images in the Normal condition included a change in the visible part of the eye along with the change in head orientation, while images in the Wollaston condition were manipulated to have identical eye regions across head orientations. Multiple regression analysis with explanatory variables of eye orientation and head orientation revealed that linear models account for most of the variance both in the Normal condition and in the Wollaston condition. Further, we found no evidence that the model with a nonlinear term explains significantly more variance. Thus, the current study supports the dual-route model that computes the perceived gaze direction as a linear combination of eye orientation and head orientation.

Face exploration dynamics differentiate men and women.

The human face is central to our everyday social interactions. Recent studies have shown that while gazing at faces, each one of us has a particular eye-scanning pattern, highly stable across time. Although variables such as culture or personality have been shown to modulate gaze behavior, we still don't know what shapes these idiosyncrasies. Moreover, most previous observations rely on static analyses of small-sized eye-position data sets averaged across time. Here, we probe the temporal dynamics of gaze to explore what information can be extracted about the observers and what is being observed. Controlling for any stimuli effect, we demonstrate that among many individual characteristics, the gender of both the participant (gazer) and the person being observed (actor) are the factors that most influence gaze patterns during face exploration. We record and exploit the largest set of eye-tracking data (405 participants, 58 nationalities) from participants watching videos of another person. Using novel data-mining techniques, we show that female gazers follow a much more exploratory scanning strategy than males. Moreover, female gazers watching female actresses look more at the eye on the left side. These results have strong implications in every field using gaze-based models from computer vision to clinical psychology.

Dynamics of unconscious contextual effects in orientation processing.

Contextual effects abound in the real world; how we perceive an object depends on what surrounds it. A classic example of this is the tilt illusion (TI) whereby the presence of a surround shifts the perceived orientation of a target. Surprisingly, the magnitude and direction of this shift depend on the orientation difference between the target and surround: when their orientations are similar, the perceived difference is amplified and the target appears repelled in orientation from the surround (i.e., the TI). However, when their orientations are close to perpendicular, the difference is decreased and the target appears attracted in orientation toward the surround (i.e., the indirect TI). These misperceptions of orientation have revealed much about the underlying detectors involved in visual processing and how they interact with each other. What remains at stake are the levels of processing involved. To examine this, we designed a reverse-correlation technique whereby observers are blind to the orientation of the surround. We find that the TI and indirect TI occur reliably and over a similar time course, supporting the role of a single mechanism underlying orientation biases that operates in the early stages of visual processing before the conscious extraction of the surround orientation.

Gaze constancy in upright and inverted faces.

The dual-route model (Otsuka, Mareschal, Calder, & Clifford, 2014) posits that constancy in the perception of gaze direction across lateral head rotation depends on the integration of information from the eye region and information about head rotation. Incorporation of information about head rotation serves to compensate for the change in eye-region information when viewing a rotated head. We tested the ability of this model to predict the magnitude of Wollaston's effect: When eyes from a frontal pose are inserted into an angled face, the perceived direction of gaze appears attracted towards the direction of the head. The framework of the dual-route model explains Wollaston's effect as a result of the misapplication of this same integration operation without any change in eye-region information. To test this explanation, we compared the magnitude of the integration occurring for Wollaston's effect to that for normal faces. Here, participants performed categorical judgment of gaze direction across head rotation poses in three image conditions: normal face, eyes-only, and Wollaston. Integration of eye and head information was inferred by comparing the effect of pose between the eyes-only condition and the normal face condition, and by examining the effect of pose in the Wollaston condition. Consistent with the dual-route model, the magnitude of integration was similar between the normal face condition and the Wollaston condition. Further, upright and inverted faces yielded similar levels of gaze constancy, showing that the dual-route model applies to the perception of gaze direction in inverted faces as well as in upright faces.

A generalized tendency toward direct gaze with uncertainty.

Joint gaze behavior plays a crucial role in nonverbal communication and enhances group interactions. We recently reported that under conditions of uncertainty, observers assume that another person's (left/right averted) gaze is directed towards them, a prior for direct gaze. Given that people's gaze can deviate in many directions during social interactions, we developed a versatile method to examine how the influence of the prior for direct gaze varies across a range of gaze directions in both forward facing and rotated heads. We find that observers tend to report another's gaze along all axes as being more direct when uncertainty is introduced by adding noise to the stimulus. We also find that the influence of the prior is stronger in rotated heads than direct (forward) heads. This is consistent with the idea that, when uncertain, humans tend to judge gaze deviations as being directed at them, regardless of head rotation or axis of deviation.

Adaptation to vergent and averted eye gaze.

Previous adaptation studies have revealed the tuning properties of mechanisms coding left-right averted gaze. Here, Experiment 1 used an adaptation procedure to investigate the mechanisms that encode vergent eye gaze. Following prolonged exposure to convergent or divergent gaze, observers were more likely to categorize smaller gaze deviations in the adapted direction as parallel (i.e., nonvergent). We then examined whether adaptation was occurring to the eyes independently (monocular gaze direction) as opposed to the two eyes as a unitary stimulus (binocular gaze direction). In Experiment 2, we interleaved presentations of convergent and divergent adaptors and tested with either congruent (vergent) or incongruent (left-right) stimuli. Similarly, we interleaved presentations of leftward- and rightward-averted adaptors and tested with congruent (left-right) and incongruent (vergent) stimuli. If adaptation were driven solely by monocular gaze direction, congruent and incongruent adaptation would be similar because, at the level of an individual eye, the stimuli are identical. We find considerable adaptation in the incongruent conditions, consistent with adaptation to individual eye directions. However, we also find greater adaptation in congruent conditions, implicating the involvement of mechanisms that encode binocular gaze direction.

Facial emotion recognition in refugee children with a history of war trauma.

Over 36 million children are currently displaced due to war, yet we know little about how these experiences of war and displacement affect their socioemotional development-notably how they perceive facial expressions. Across three different experiments, we investigated the effects of war trauma exposure on facial emotion recognition in Syrian refugee (n = 130, Mage = 9.3 years, 63 female) and Jordanian nonrefugee children (n = 148, Mage = 9.4 years, 66 female) living in Jordan (data collected 2019-2020). Children in the two groups differed in trauma exposure, but not on any of our measures of mental health. In Experiment 1, we measured children's biases to perceive an emotion using morphed facial expressions and found no evidence that biases differed between refugees and nonrefugees. In Experiment 2, we adapted a novel perceptual scaling task that bypasses semantic knowledge, and again found no differences between the two group's discrimination of facial expressions. Finally, in Experiment 3, we recorded children's eye movements as they identified Middle Eastern actors' facial expressions, and again found no differences between the groups in either their identification accuracies or scanning strategies. Taken together, our results suggest that exposure to war-related trauma and displacement during early development, when reported by the caregiver but not always recollected by the child, does not appear to alter emotion recognition of facial expressions. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Genetic algorithms reveal identity independent representation of emotional expressions.

People readily and automatically process facial emotion and identity, and it has been reported that these cues are processed both dependently and independently. However, this question of identity independent encoding of emotions has only been examined using posed, often exaggerated expressions of emotion, that do not account for the substantial individual differences in emotion recognition. In this study, we ask whether people's unique beliefs of how emotions should be reflected in facial expressions depend on the identity of the face. To do this, we employed a genetic algorithm where participants created facial expressions to represent different emotions. Participants generated facial expressions of anger, fear, happiness, and sadness, on two different identities. Facial features were controlled by manipulating a set of weights, allowing us to probe the exact positions of faces in high-dimensional expression space. We found that participants created facial expressions belonging to each identity in a similar space that was unique to the participant, for angry, fearful, and happy expressions, but not sad. However, using a machine learning algorithm that examined the positions of faces in expression space, we also found systematic differences between the two identities' expressions across participants. This suggests that participants' beliefs of how an emotion should be reflected in a facial expression are unique to them and identity independent, although there are also some systematic differences in the facial expressions between two identities that are common across all individuals. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Maternal Trauma and Psychopathology Symptoms Affect Refugee Children's Mental Health But Not Their Emotion Processing.

Refugee children's development may be affected by their parents' war-related trauma exposure and psychopathology symptoms across a range of cognitive and affective domains, but the processes involved in this transmission are poorly understood. Here, we investigated the impact of refugee mothers' trauma exposure and mental health on their children's mental health and attention biases to emotional expressions. In our sample of 324 Syrian refugee mother-child dyads living in Jordan (children's Mage=6.32, SD = 1.18; 50% female), mothers reported on their symptoms of anxiety and depression, and on their children's internalising, externalising, and attention problems. A subset of mothers reported their trauma exposure (n = 133) and PTSD symptoms (n = 124). We examined emotion processing in the dyads using a standard dot-probe task measuring their attention allocation to facial expressions of anger and sadness. Maternal trauma and PTSD symptoms were linked to child internalising and attention problems, while maternal anxiety and depression symptoms were associated with child internalising, externalising, and attention problems. Mothers and children were hypervigilant towards expressions of anger, but surprisingly, mother and child biases were not correlated with each other. The attentional biases to emotional faces were also not linked to psychopathology risk in the dyads. Our findings highlight the importance of refugee mothers' trauma exposure and psychopathology on their children's wellbeing. The results also suggest a dissociation between the mechanisms underlying mental health and those involved in attention to emotional faces, and that intergenerational transmission of mental health problems might involve mechanisms other than attentional processes relating to emotional expressions.