Task Demands Modulate Effects of Threatening Faces on Early Perceptual Encoding

Predictability modulates the early neural coding of spatially unattended fearful faces

In this study, we assessed whether predictability affected the early processing of facial expressions. To achieve this, we measured lateralised early- and mid-latency event-related potentials associated with visual processing. Twenty-two participants were shown pairs of bilaterally presented fearful, happy, angry, or scrambled faces. Participants were required to identify angry faces on a spatially attended side whilst ignoring happy, fearful, and scrambled faces. Each block began with the word HAPPY or FEARFUL which informed participants the probability at which these faces would appear. Attention effects were found for the lateralised P1, suggesting that emotions do not modulate the P1 differentially, nor do predictions relating to emotions. Pairwise comparisons demonstrated that, when spatially unattended, unpredicted fearful faces produced larger lateralised N170 amplitudes compared to predicted fearful faces and unpredicted happy faces. Finally, attention towards faces increased lateralised EPN amplitudes, as did both fearful expressions and low predictability. Thus, we demonstrate that the N170 and EPN are sensitive to top-down predictions relating to facial expressions and that low predictability appears to specifically affect the early encoding of fearful faces when unattended, possibly to initiate attentional capture.

The Timing of Gaze Direction Perception: ERP Decoding and Task Modulation

Distinguishing the direction of another person's eye gaze is extremely important in everyday social interaction, as it provides critical information about people's attention and, therefore, intentions. The temporal dynamics of gaze processing have been investigated using event-related potentials (ERPs) recorded with electroencephalography (EEG). However, the moment at which our brain distinguishes the gaze direction (GD), irrespectively of other facial cues, remains unclear. To solve this question, the present study aimed to investigate the time course of gaze direction processing, using an ERP decoding approach, based on the combination of a support vector machine and error-correcting output codes. We recorded EEG in young healthy subjects, 32 of them performing GD detection and 34 conducting face orientation tasks. Both tasks presented 3D realistic faces with five different head and gaze orientations each: 30°, 15° to the left or right, and 0°. While the classical ERP analyses did not show clear GD effects, ERP decoding analyses revealed that discrimination of GD, irrespective of head orientation, started at 140 ms in the GD task and at 120 ms in the face orientation task. GD decoding accuracy was higher in the GD task than in the face orientation task and was the highest for the direct gaze in both tasks. These findings suggest that the decoding of brain patterns is modified by task relevance, which changes the latency and the accuracy of GD decoding.

Reward History Modulates the Processing of Task-Irrelevant Emotional Faces in a Demanding Task

The aim of the current study was to examine how reward-associated emotional facial distractors could capture attentional resources in a demanding visual task using event-related potentials (ERPs). In the learning phase, a high- or low-reward probability was paired with angry, happy, or neutral faces. Then, in the test phase, participants performed a face-irrelevant task with no reward at stake, in which they needed to discriminate the length of two lines presented in the center of the screen while faces that were taken from the learning phase were used as distractors presented in the periphery. The behavioral results revealed no effect of distractor emotional valence since the emotional information was task-irrelevant. The ERP results in the test phase revealed a significant main effect of distractor emotional valence for the parieto-occipital P200 (170-230 ms); the mean amplitudes in both the angry- and happy-face conditions were more positive than the neutral-face condition. Moreover, we found that the high-reward association enhanced both the N170 (140-180 ms) and EPN (260-330 ms) relative to the low-reward association condition. Finally, the N2pc (270-320 ms) also exhibited enhanced neural activity in the high-reward condition compared to the low-reward condition. The absence of emotional effects indicated that task-irrelevant emotional facial stimuli did not impact behavioral or neural responses in this highly demanding task. However, reward-associated information was processed when attention was directed elsewhere, suggesting that the processing of reward-associated information worked more in an automatic way, irrespective of the top-down task demand.

Attentional demand induced by visual crowding modulates the anger superiority effect

Previous research on emotional bias in face perception has shown inconsistent findings, proposing either angry or happy faces to be detected more efficiently. A recent study showed that the anger superiority effect (ASE), which showed in the high attentional demand condition, vanished in the low attentional demand condition. The authors thus proposed an attentional demands modulation hypothesis to interpret the inconsistent findings. The present study tested this hypothesis in a visual crowding task in which participants were instructed to determine whether the target face was happy or angry. Attentional demands were manipulated by changing the strength of crowding, including presenting stimuli in different configurations (Experiment 1), and setting different target-flanker separations and presenting stimuli in different eccentricities (Experiment 2). Experiment 1 showed an ASE when the stimulus configuration incurred a high attentional demand. Intriguingly, the ASE became weaker and then disappeared as the attentional demand became lower. Experiment 2 replicated this finding and showed that the ASE decreased as the target-flanker separation became larger. Together, these results suggest that the emergence and magnitude of ASE is modulated by attentional demands, which supports the attentional demands modulation hypothesis.

Working memory guidance of visual attention to threat in offenders

Aggression and trait anger have been linked to attentional biases toward angry faces and attribution of hostile intent in ambiguous social situations. Memory and emotion play a crucial role in social-cognitive models of aggression but their mechanisms of influence are not fully understood. Combining a memory task and a visual search task, this study investigated the guidance of attention allocation toward naturalistic face targets during visual search by visual working memory (WM) templates in 113 participants who self-reported having served a custodial sentence. Searches were faster when angry faces were held in working memory regardless of the emotional valence of the visual search target. Higher aggression and trait anger predicted increased working memory modulated attentional bias. These results are consistent with the Social-Information Processing model, demonstrating that internal representations bias attention allocation to threat and that the bias is linked to aggression and trait anger.

Human face and gaze perception is highly context specific and involves bottom-up and top-down neural processing

This review summarizes human perception and processing of face and gaze signals. Face and gaze signals are important means of non-verbal social communication. The review highlights that: (1) some evidence is available suggesting that the perception and processing of facial information starts in the prenatal period; (2) the perception and processing of face identity, expression and gaze direction is highly context specific, the effect of race and culture being a case in point. Culture affects by means of experiential shaping and social categorization the way in which information on face and gaze is collected and perceived; (3) face and gaze processing occurs in the so-called 'social brain'. Accumulating evidence suggests that the processing of facial identity, facial emotional expression and gaze involves two parallel and interacting pathways: a fast and crude subcortical route and a slower cortical pathway. The flow of information is bi-directional and includes bottom-up and top-down processing. The cortical networks particularly include the fusiform gyrus, superior temporal sulcus (STS), intraparietal sulcus, temporoparietal junction and medial prefrontal cortex.

Early ERP functions are indexed by lateralized effects to peripherally presented emotional faces and scrambles

A large body of research suggests that early event-related potentials (ERPs), such as the P1 and N1, are potentiated by attention and represent stimulus amplification. However, recent accounts suggest that the P1 is associated with inhibiting the irrelevant visual field evidenced by a pronounced ipsilateral P1 during sustained attention to peripherally presented stimuli. The current EEG study further investigated this issue to reveal how lateralized ERP findings are modulated by face and emotional information. Therefore, participants were asked to fixate the center of the screen and pay sustained attention either to the right or left visual field, where angry or neutral faces or their Fourier phase-scrambled versions were presented. We found a bilateral P1 to all stimuli with relatively increased, but delayed, ipsilateral P1 amplitudes to faces but not to scrambles. Explorative independent component analyses dissociated an earlier lateralized larger contralateral P1 from a later bilateral P1. By contrast, the N170 showed a contralateral enhancement to all stimuli, which was most pronounced for neutral faces attended in the left hemifield. Finally, increased contralateral alpha power was found for both attended hemifields but was not significantly related to poststimulus ERPs. These results provide evidence against a general inhibitory role of the P1 but suggest stimulus-specific relative enhancements of the ipsilateral P1 for the irrelevant visual hemifield. The lateralized N170, however, is associated with stimulus amplification as a function of facial features.

Emotion, Gender and Gaze Discrimination Tasks do not Differentially Impact the Neural Processing of Angry or Happy Facial Expressions-a Mass Univariate ERP Analysis

Facial expression processing is a critical component of social cognition yet, whether it is influenced by task demands at the neural level remains controversial. Past ERP studies have found mixed results with classic statistical analyses, known to increase both Type I and Type II errors, which Mass Univariate statistics (MUS) control better. However, MUS open-access toolboxes can use different fundamental statistics, which may lead to inconsistent results. Here, we compared the output of two MUS toolboxes, LIMO and FMUT, on the same data recorded during the processing of angry and happy facial expressions investigated under three tasks in a within-subjects design. Both toolboxes revealed main effects of emotion during the N170 timing and main effects of task during later time points typically associated with the LPP component. Neither toolbox yielded an interaction between the two factors at the group level, nor at the individual level in LIMO, confirming that the neural processing of these two face expressions is largely independent from task demands. Behavioural data revealed main effects of task on reaction time and accuracy, but no influence of expression or an interaction between the two. Expression processing and task demands are discussed in the context of the consistencies and discrepancies between the two toolboxes and existing literature.

Attention is prioritised for proximate and approaching fearful faces

Attention is an important function that allows us to selectively enhance the processing of relevant stimuli in our environment. Fittingly, a number of studies have revealed that potentially threatening/fearful stimuli capture attention more efficiently. Interestingly, in separate fMRI studies, threatening stimuli situated close to viewers were found to enhance brain activity in fear-relevant areas more than stimuli that were further away. Despite these observations, few studies have examined the effect of personal distance on attentional capture by emotional stimuli. Using electroencephalography (EEG), the current investigation addressed this question by investigating attentional capture of emotional faces that were either looming/receding, or were situated at different distances from the viewer. In Experiment 1, participants carried out an incidental task while looming or receding fearful and neutral faces were presented bilaterally. A significant lateralised N170 and N2pc were found for a looming upright fearful face, however no significant components were found for a looming upright neutral face or inverted fearful and neutral faces. In Experiment 2, participants made gender judgements of emotional faces that appeared on a screen situated within or beyond peripersonal space (respectively 50 cm or 120 cm). Although response times did not differ, significantly more errors were made when faces appeared in near as opposed to far space. Importantly, ERPs revealed a significant N2pc for fearful faces presented in peripersonal distance, compared to the far distance. Our findings show that personal distance markedly affects neural responses to emotional stimuli, with increased attention towards fearful upright faces that appear in close distance.

Influence of Attention Control on Implicit and Explicit Emotion Processing of Face and Body: Evidence From Flanker and Same-or-Different Paradigms

Many existing findings indicate that processing of emotional information is pre-attentive, largely immune from attentional control. Nevertheless, inconsistent evidence on the interference of emotional cues on cognitive processing suggests that this influence may be a highly conditional phenomenon. The aim of the present study was twofold: (1) to examine the modulation of attention control on emotion processing using facial expressions (2) explore the very same effect for emotional body expressions. In Experiment 1, participants performed a Flanker task in which they had to indicate either the emotion (happy/fearful) or the gender of the target stimulus while ignoring the distracting stimuli at the side. We found evidence for intrusion of the emotional dimension of a stimulus in both the emotion and gender discrimination performance, thus when either task-relevant or task-irrelevant. To further explore the influence of attention control mechanisms, in Experiment 2 participants performed a same-or-different judgment task in which they were asked to pay attention to both the central and lateral stimuli and indicated whether the central stimulus matched the lateral for emotion or gender. Results showed that emotional features exerted an influence at an implicit level (i.e., during gender judgments) for bodies only. Gender features did not affect emotional processing in either experiments. To rule out the possibility that this effect was driven by postural rather than emotional features of fearful vs. happy stimuli, a control experiment was conducted. In Experiment 3, bodies with an opening/up-ward or closing/down-ward posture but with no emotional valence were presented. Results revealed that the body posture did not influence gender discrimination. Findings suggest that the emotional valence of a face or body stimulus can overpass attention filtering mechanisms, independently from the level of attentional modulation (Experiment 1). However, broadening the focus of attention to include the lateral stimuli led emotional information to intrude on the main task, exerting an implicit, bottom–up influence on gender processing, only when conveyed by bodies (Experiment 2). Results point to different mechanisms for the implicit processing of face and body emotional expressions, with the latter likely having role on action preparation processes.