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.

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.

Uncoupling Sensation and Perception in Human Time Processing.

Timing emerges from a hierarchy of computations ranging from early encoding of physical duration (time sensation) to abstract time representations (time perception) suitable for storage and decisional processes. However, the neural basis of the perceptual experience of time remains elusive. To address this, we dissociate brain activity uniquely related to lower-level sensory and higher-order perceptual timing operations, using event-related fMRI. Participants compared subsecond (500 msec) sinusoidal gratings drifting with constant velocity (standard) against two probe stimuli: (1) control gratings drifting at constant velocity or (2) accelerating gratings, which induced illusory shortening of time. We tested two probe intervals: a 500-msec duration (Short) and a longer duration required for an accelerating probe to be perceived as long as the standard (Long-individually determined). On each trial, participants classified the probe as shorter or longer than the standard. This allowed for comparison of trials with an "Objective" (physical) or "Subjective" (perceived) difference in duration, based on participant classifications. Objective duration revealed responses in bilateral early extrastriate areas, extending to higher visual areas in the fusiform gyrus (at more lenient thresholds). By contrast, Subjective duration was reflected by distributed responses in a cortical/subcortical areas. This comprised the left superior frontal gyrus and the left cerebellum, and a wider set of common timing areas including the BG, parietal cortex, and posterior cingulate cortex. These results suggest two functionally independent timing stages: early extraction of duration information in sensory cortices and Subjective experience of duration in a higher-order cortical-subcortical timing areas.

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.

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.

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).

Expression perceptive fields explain individual differences in the recognition of facial emotions.

Humans can use the facial expressions of another to infer their emotional state, although it remains unknown how this process occurs. Here we suppose the presence of perceptive fields within expression space, analogous to feature-tuned receptive-fields of early visual cortex. We developed genetic algorithms to explore a multidimensional space of possible expressions and identify those that individuals associated with different emotions. We next defined perceptive fields as probabilistic maps within expression space, and found that they could predict the emotions that individuals infer from expressions presented in a separate task. We found profound individual variability in their size, location, and specificity, and that individuals with more similar perceptive fields had similar interpretations of the emotion communicated by an expression, providing possible channels for social communication. Modelling perceptive fields therefore provides a predictive framework in which to understand how individuals infer emotions from facial expressions.

The time course of the spatial representation of 'past' and 'future' concepts: New evidence from the STEARC effect.

Humans use space to think of and communicate the flow of time. This spatial representation of time is influenced by cultural habits so that in left-to-right reading cultures, short durations and past events are mentally positioned to the left of long durations and future events. The STEARC effect (Space Temporal Association of Response Codes) shows a faster classification of short durations/past events with responses on the left side of space and of long durations/future events with responses on the right side. We have recently showed that during the classification of time durations, space is a late heuristic of time because in this case, the STEARC appears only when manual responses are slow, not when they are fast. Here, we wished to extend this observation to the semantic classification of words as referring to the 'past' or the 'future'. We hypothesised that the semantic processing of 'past' and 'future' concepts would have engaged slower decision processes than the classification of short versus long time durations. According to dual-route models of conflict tasks, if the task-dependent classification/decision process were to proceed relatively slowly, then the effects of direct activation of culturally preferred links between stimulus and response (S-R), i.e., past/left and future/right in the case of the present task, should attain higher amplitudes before the instruction-dependent correct response is selected. This would imply that, at variance with the faster classification of time durations, during the slower semantic classification of time concepts, in incongruent trials, the direct activation of culturally preferred S-R links should introduce significant reaction time (RT) costs and a corresponding STEARC at the fastest manual responses in the experiment too. The study's results confirmed this hypothesis and showed that in the classification of temporal words, the STEARC also increased as a function of the length of RTs. Taken together, the results from sensory duration and semantic classification STEARC tasks show that the occurrence, strength and time course of the STEARC varies significantly as a function of the speed and level of cognitive processing required in the task.

Space is a late heuristic of elapsing time: New evidence from the STEARC effect.

To get a concrete representation of its intangible flow, culture frames elapsing time along spatially oriented mental or graphical lines, which are organised according to reading habits, from left to right in western cultures. One of the strongest evidence for this spatial representation of time is the STEARC effect (Spatial-Temporal Association of Response Codes), which consists of faster coding of "short" durations with motor responses in the left side of space and of "long" durations with responses in the right side. Here, we investigated the STEARC as a function of response speed in two different experiments in healthy participants. Surprisingly, in both sub- and supra-second ranges, we found the STEARC only when decisions on time durations were slow, while no spatial representation of time was present with fast decisions. This first demonstrates that space slowly takes over faster non-spatial processing of time flow and that it is possible to empirically separate the behavioural manifestations of the non-spatial and the nurtured spatial mechanisms of time coding.

Time-dilation and time-contraction in an anisochronous and anisometric visual scenery.

Several studies show that visual stimuli traveling at higher velocities are overestimated with respect to slower, or stationary, stimuli of equivalent physical duration. This effect-time dilation-relates more in general to several accounts highlighting a quantitative relationship between the amount of changes a stimulus is subject to and the perceived duration: faster stimuli, subject to a greater number of changes in space, lead to overestimated durations of displacement. In the present paper we provide evidence of a new illusory effect, in which the apparent duration of a sensory event is affected by the way a constant number of changes are delivered in time, or in time and space. Participants judged accelerating and decelerating sequences of stationary flickering stimuli (Experiments 1 and 3) and accelerating and decelerating horizontally drifting visual stimuli (Experiment 2) on the fronto-parallel plane. Acceleration and deceleration were achieved by irregular sequencing of events in time (anisochronous flicker rate) or irregular sequencing of events in time and space (anisochronous and/or anisometric drift). Despite being characterized by the same amounts of visual changes, accelerating and decelerating sequences lead to opposite duration biases (underestimation and overestimation errors, respectively). We refer to this effect in terms of ATI: Aniso-Time-Illusion. This bias was observed in both subsecond (760 ms) and suprasecond ranges (1900 ms). These data highlight how the spatio-temporal evolution of dynamic visual events, asides the overall quantity of changes they are subject to, affect the perceived amount of time they require to unfold.

Social synchronization of brain activity increases during eye-contact.

Humans make eye-contact to extract information about other people's mental states, recruiting dedicated brain networks that process information about the self and others. Recent studies show that eye-contact increases the synchronization between two brains but do not consider its effects on activity within single brains. Here we investigate how eye-contact affects the frequency and direction of the synchronization within and between two brains and the corresponding network characteristics. We also evaluate the functional relevance of eye-contact networks by comparing inter- and intra-brain networks of friends vs. strangers and the direction of synchronization between leaders and followers. We show that eye-contact increases higher inter- and intra-brain synchronization in the gamma frequency band. Network analysis reveals that some brain areas serve as hubs linking within- and between-brain networks. During eye-contact, friends show higher inter-brain synchronization than strangers. Dyads with clear leader/follower roles demonstrate higher synchronization from leader to follower in the alpha frequency band. Importantly, eye-contact affects synchronization between brains more than within brains, demonstrating that eye-contact is an inherently social signal. Future work should elucidate the causal mechanisms behind eye-contact induced synchronization.

Randomized comparison between tirofiban and abciximab to promote complete ST-resolution in primary angioplasty: results of the facilitated angioplasty with tirofiban or abciximab (FATA) in ST-elevation myocardial infarction trial.

AIMS: To test the equivalence of high-dose bolus (HDB) tirofiban vs. abciximab during primary percutaneous coronary intervention (PPCI) in terms of ST-segment resolution (STR). METHODS AND RESULTS: The FATA trial (Facilitated Angioplasty with Tirofiban or Abciximab) was a prospective, multicentre, open-label trial that enrolled 692 patients with ST-segment elevation myocardial infarction (STEMI) undergoing PPCI. Patients were randomized 1:1 to receive abciximab (n = 341) or HDB tirofiban (n = 351). Primary endpoint was the rate of complete (> or =70%) STR 90 min after first balloon inflation. Thirty-day incidence of major bleedings, death, re-infarction and new revascularizations was also evaluated. Baseline characteristics of the two groups were well-balanced, with the exception of previous MI rates (tirofiban 6% vs. abciximab 2.6%, P = 0.03). The procedure was successful in 96.7% of the abciximab and in 96.6% of the tirofiban cohort (P = 0.94). Complete STR was obtained in 67.05% of the tirofiban and 70.45% of the abciximab group (Delta -3.4%, 95% confidence interval -10.35 to +3.56), which falls beyond the predefined Delta +/- 10% equivalence boundaries. Rates of secondary endpoints were similar between the two groups. CONCLUSION: This study failed to show the equivalence of HBD of tirofiban and abciximab as adjunctive therapy to PPCI.

Assumptions about the positioning of virtual stimuli affect gaze direction estimates during Augmented Reality based interactions.

We investigated gaze direction determination in dyadic interactions mediated by an Augmented Reality (AR) head-mounted-display. With AR, virtual content is overlaid on top of the real-world scene, offering unique data visualization and interaction opportunities. A drawback of AR however is related to uncertainty regarding the AR user's focus of attention in social-collaborative settings: an AR user looking in our direction might either be paying attention to us or to augmentations positioned somewhere in between. In two psychophysical experiments, we assessed what impact assumptions concerning the positioning of virtual content attended by an AR user have on other people's sensitivity to their gaze direction. In the first experiment we found that gaze discrimination was better when the participant was aware that the AR user was focusing on stimuli positioned on their depth plane as opposed to being positioned halfway between the AR user and the participant. In the second experiment, we found that this modulatory effect was explained by participants' assumptions concerning which plane the AR user was focusing on, irrespective of these being correct. We discuss the significance of AR reduced gaze determination in social-collaborative settings as well as theoretical implications regarding the impact of this technology on social behaviour.

Selective binding of facial features reveals dynamic expression fragments.

The temporal correspondence between two arbitrarily chosen pairs of alternating features can generally be reported for rates up to 3-4 Hz. This limit is however surpassed for specialised visual mechanisms that encode conjunctions of features. Here we show that this 3-4 Hz limit is exceeded for eye gaze and eyebrow pairing, but not for eye gaze and mouth pairing, suggesting combined eye and eyebrow motion constitutes a dynamic expression fragment; a building block of superordinate facial actions.

Time-Order Errors in Duration Judgment Are Independent of Spatial Positioning.

Time-order errors (TOEs) occur when the discriminability between two stimuli are affected by the order in which they are presented. While TOEs have been studied since the 1860s, it is unknown whether the spatial properties of a stimulus will affect this temporal phenomenon. In this experiment, we asked whether perceived duration, or duration discrimination, might be influenced by whether two intervals in a standard two-interval method of constants paradigm were spatially overlapping in visual short-term memory. Two circular sinusoidal gratings (one standard and the other a comparison) were shown sequentially and participants judged which of the two was presented for a longer duration. The test stimuli were either spatially overlapping (in different spatial frames) or separate. Stimulus order was randomized between trials. The standard stimulus lasted 600 ms, and the test stimulus had one of seven possible values (between 300 and 900 ms). There were no overall significant differences observed between spatially overlapping and separate stimuli. However, in trials where the standard stimulus was presented second, TOEs were greater, and participants were significantly less sensitive to differences in duration. TOEs were also greater in conditions involving a saccade. This suggests there is an intrinsic memory component to two interval tasks in that the information from the first interval has to be stored; this is more demanding when the standard is presented in the second interval. Overall, this study suggests that while temporal information may be encoded in some spatial form, it is not dependent on visual short-term memory.

Temporal Order Judgements of Dynamic Gaze Stimuli Reveal a Postdictive Prioritisation of Averted Over Direct Shifts.

We studied temporal order judgements (TOJs) of gaze shift behaviours and evaluated the impact of gaze direction (direct and averted gaze) and face context information (both eyes set within a single face or each eye within two adjacent hemifaces) on TOJ performance measures. Avatar faces initially gazed leftwards or rightwards (Starting Gaze Direction). This was followed by sequential and independent left and right eye gaze shifts with various amounts of stimulus onset asynchrony. Gaze shifts could be either Matching (both eyes end up pointing direct or averted) or Mismatching (one eye ends up pointing direct, the other averted). Matching shifts revealed an attentional cueing mechanism, where TOJs were biased in favour of the eye lying in the hemispace cued by the avatar's Starting Gaze Direction. For example, the left eye was more likely to be judged as shifting first when the avatar initially gazed toward the left side of the screen. Mismatching shifts showed biased TOJs in favour of the eye performing the averted shift, but only in the context of two separate hemifaces that does not violate expectations of directional gaze shift congruency. This suggests a postdictive inferential strategy that prioritises eye movements based on the type of gaze shift, independently of where attention is initially allocated. Averted shifts are prioritised over direct, as these might signal the presence of behaviourally relevant information in the environment.

Pupil response hazard rates predict perceived gaze durations.

We investigated the mechanisms for evaluating perceived gaze-shift duration. Timing relies on the accumulation of endogenous physiological signals. Here we focused on arousal, measured through pupil dilation, as a candidate timing signal. Participants timed gaze-shifts performed by face stimuli in a Standard/Probe comparison task. Pupil responses were binned according to "Longer/Shorter" judgements in trials where Standard and Probe were identical. This ensured that pupil responses reflected endogenous arousal fluctuations opposed to differences in stimulus content. We found that pupil hazard rates predicted the classification of sub-second intervals (steeper dilation = "Longer" classifications). This shows that the accumulation of endogenous arousal signals informs gaze-shift timing judgements. We also found that participants relied exclusively on the 2nd stimulus to perform the classification, providing insights into timing strategies under conditions of maximum uncertainty. We observed no dissociation in pupil responses when timing equivalent neutral spatial displacements, indicating that a stimulus-dependent timer exploits arousal to time gaze-shifts.

Pupil dilation as an index of preferred mutual gaze duration.

Most animals look at each other to signal threat or interest. In humans, this social interaction is usually punctuated with brief periods of mutual eye contact. Deviations from this pattern of gazing behaviour generally make us feel uncomfortable and are a defining characteristic of clinical conditions such as autism or schizophrenia, yet it is unclear what constitutes normal eye contact. Here, we measured, across a wide range of ages, cultures and personality types, the period of direct gaze that feels comfortable and examined whether autonomic factors linked to arousal were indicative of people's preferred amount of eye contact. Surprisingly, we find that preferred period of gaze duration is not dependent on fundamental characteristics such as gender, personality traits or attractiveness. However, we do find that subtle pupillary changes, indicative of physiological arousal, correlate with the amount of eye contact people find comfortable. Specifically, people preferring longer durations of eye contact display faster increases in pupil size when viewing another person than those preferring shorter durations. These results reveal that a person's preferred duration of eye contact is signalled by physiological indices (pupil dilation) beyond volitional control that may play a modulatory role in gaze behaviour.

The effect of self-efficacy on visual discrimination sensitivity.

Can subjective belief about one's own perceptual competence change one's perception? To address this question, we investigated the influence of self-efficacy on sensory discrimination in two low-level visual tasks: contrast and orientation discrimination. We utilised a pre-post manipulation approach whereby two experimental groups (high and low self-efficacy) and a control group made objective perceptual judgments on the contrast or the orientation of the visual stimuli. High and low self-efficacy were induced by the provision of fake social-comparative performance feedback and fictional research findings. Subsequently, the post-manipulation phase was performed to assess changes in visual discrimination thresholds as a function of the self-efficacy manipulations. The results showed that the high self-efficacy group demonstrated greater improvement in visual discrimination sensitivity compared to both the low self-efficacy and control groups. These findings suggest that subjective beliefs about one's own perceptual competence can affect low-level visual processing.