Selective facial mimicry of native over foreign speakers in preverbal infants

Optimal processing of surface facial EMG to identify emotional expressions: A data-driven approach

Surface facial electromyography (EMG) is commonly used to detect emotions from subtle facial expressions. Although there are established procedures for collecting EMG data and some aspects of their processing, there is little agreement among researchers about the optimal way to process the EMG signal, so that the study-unrelated variability (noise) is removed, and the emotion-related variability is best detected. The aim of the current paper was to establish an optimal processing pipeline for EMG data for identifying emotional expressions in facial muscles. We identified the most common processing steps from existing literature and created 72 processing pipelines that represented all the different processing choices. We applied these pipelines to a previously published dataset from a facial mimicry experiment, where 100 adult participants observed happy and sad facial expressions, whilst the activity of their facial muscles, zygomaticus major and corrugator supercilii, was recorded with EMG. We used a resampling approach and subsets of the original data to investigate the effect and robustness of different processing choices on the performance of a logistic regression model that predicted the mimicked emotion (happy/sad) from the EMG signal. In addition, we used a random forest model to identify the most important processing steps for the sensitivity of the logistic regression model. Three processing steps were found to be most impactful: baseline correction, standardisation within muscles, and standardisation within subjects. The chosen feature of interest and the signal averaging had little influence on the sensitivity to the effect. We recommend an optimal processing pipeline, share our code and data, and provide a step-by-step walkthrough for researchers.

Combining wearable fNIRS and immersive virtual reality to study preschoolers' social development: a proof-of-principle study on preschoolers' social preference

A child's social world is complex and rich, but has traditionally been assessed with conventional experiments where children are presented with repeated stimuli on a screen. These assessments are impoverished relative to the dynamics of social interactions in real life, and can be challenging to implement with preschoolers, who struggle to comply with strict lab rules. The current work meets the need to develop new platforms to assess preschoolers' social development, by presenting a unique virtual-reality set-up combined with wearable functional near-infrared spectroscopy (fNIRS). As a proof-of-principle, we validated this platform by measuring brain activity during self-guided social interaction in 3-to-5-year-olds, which is under-investigated, yet crucial to understand the basis of social interactions in preschoolers. 37 preschoolers chose an interaction partner from one of 4 human-like avatars of different gender and age. We recorded spontaneous brain fluctuations from the frontal and temporoparietal regions (notably engaged in social-categorization and preference) while children played a bubble-popping game with a preferred and an assigned avatar. 60% of the participants chose to play with the same-gender and same-age avatar. However, this result was driven by females (>80% vs. 50% in males). Different fronto-temporoparietal connectivity patterns when playing with the two avatars were observed, especially in females. We showed the feasibility of using a novel set-up to naturalistically assess social preference in preschoolers, which was assessed at the behavioural and functional connectivity level. This work provides a first proof-of-principle for using cutting-edge technologies and naturalistic experiments to study social development, opening new avenues of research.

Facial mimicry is not modulated by dopamine D2/3 and opioid receptor antagonism

RATIONALE

According to theories of embodied cognition, facial mimicry - the spontaneous, low-intensity imitation of a perceived emotional facial expression - is first an automatic motor response, whose accompanying proprioceptive feedback contributes to emotion recognition. Alternative theoretical accounts, however, view facial mimicry as an emotional response to a rewarding stimulus, and/or an affiliative signal, and thus reject the view of an automatic motor copy.

OBJECTIVES

To contribute to this debate and further investigate the neural basis of facial mimicry, as well as its relation to reward processing, we measured facial reactions to dynamic happy and angry faces after pharmacologically manipulating the opioid and dopamine systems - respectively, thought to subserve 'liking' and 'wanting' of rewards.

METHODS

In a placebo-controlled, double-blind experiment, 130 volunteers received in a between-subjects design 50 mg of the opioidergic antagonist naltrexone, 400 mg of the dopaminergic antagonist amisulpride, or placebo.

RESULTS

Clear occurrence of facial mimicry, measured 4 h after drug intake with electromyography (EMG) of the zygomaticus major and corrugator supercilii muscles, was found. However, facial mimicry was not affected by either compound, as shown with both frequentist statistics, and a Bayesian asymptotic regression model.

CONCLUSIONS

This null finding does not support the hypothesis that facial mimicry (of happiness) reflects an emotional response to a rewarding stimulus, leaving open the possibility of facial mimicry being an automatic motor copy. The results are relevant to the discussion about the psychological nature and the neural basis of facial mimicry, although they should be considered preliminary, given the challenges of interpreting null findings when targeting a novel effect of unknown size.

The neural correlates of inhibitory control in 10-month-old infants: A functional near-infrared spectroscopy study

Inhibitory control, a core executive function, emerges in infancy and develops rapidly across childhood. Methodological limitations have meant that studies investigating the neural correlates underlying inhibitory control in infancy are rare. Employing functional near-infrared spectroscopy alongside a novel touchscreen task that measures response inhibition, this study aimed to uncover the neural underpinnings of inhibitory control in 10-month-old infants (N = 135). We found that when inhibition was required, the right prefrontal and parietal cortices were more activated than when there was no inhibitory demand. This demonstrates that inhibitory control in infants as young as 10 months of age is supported by similar brain areas as in older children and adults. With this study we have lowered the age-boundary for localising the neural substrates of response inhibition to the first year of life.

Collective Rhythm as an Emergent Property During Human Social Coordination

The literature on social interactions has shown that participants coordinate not only at the behavioral but also at the physiological and neural levels, and that this coordination gives a temporal structure to the individual and social dynamics. However, it has not been fully explored whether such temporal patterns emerge during interpersonal coordination beyond dyads, whether this phenomenon arises from complex cognitive mechanisms or from relatively simple rules of behavior, or which are the sociocultural processes that underlie this phenomenon. We review the evidence for the existence of group-level rhythmic patterns that result from social interactions and argue that the complexity of group dynamics can lead to temporal regularities that cannot be predicted from the individual periodicities: an emergent collective rhythm. Moreover, we use this interpretation of the literature to discuss how taking into account the sociocultural niche in which individuals develop can help explain the seemingly divergent results that have been reported on the social influences and consequences of interpersonal coordination. We make recommendations on further research to test these arguments and their relationship to the feeling of belonging and assimilation experienced during group dynamics.

Sensorimotor Activity and Network Connectivity to Dynamic and Static Emotional Faces in 7-Month-Old Infants

The present study investigated whether, as in adults, 7-month-old infants’ sensorimotor brain areas are recruited in response to the observation of emotional facial expressions. Activity of the sensorimotor cortex, as indexed by µ rhythm suppression, was recorded using electroencephalography (EEG) while infants observed neutral, angry, and happy facial expressions either in a static (N = 19) or dynamic (N = 19) condition. Graph theory analysis was used to investigate to which extent neural activity was functionally localized in specific cortical areas. Happy facial expressions elicited greater sensorimotor activation compared to angry faces in the dynamic experimental condition, while no difference was found between the three expressions in the static condition. Results also revealed that happy but not angry nor neutral expressions elicited a significant right-lateralized activation in the dynamic condition. Furthermore, dynamic emotional faces generated more efficient processing as they elicited higher global efficiency and lower networks’ diameter compared to static faces. Overall, current results suggest that, contrarily to neutral and angry faces, happy expressions elicit sensorimotor activity at 7 months and dynamic emotional faces are more efficiently processed by functional brain networks. Finally, current data provide evidence of the existence of a right-lateralized activity for the processing of happy facial expressions.

Automatic imitation in youngsters with Gilles de la Tourette syndrome: A behavioral study

It is widely known that humans have a tendency to imitate each other and that appropriate modulation of automatic imitative behaviors has a crucial function in social interactions. Gilles de la Tourette syndrome (GTS) is a childhood-onset neuropsychiatric disorder characterized by motor and phonic tics. Apart from tics, patients with GTS are often reported to show an abnormal tendency to automatically imitate others' behaviors (i.e., echophenomena), which may be related to a failure in top-down inhibition of imitative response tendencies. The aim of the current study is to explore the top-down inhibitory mechanisms on automatic imitative behaviors in youngsters with GTS. Error rates and reaction times from 32 participants with GTS and 32 controls were collected in response to an automatic imitation task assessing the influence of observed movements displayed in the first-person perspective on congruent and incongruent motor responses. Results showed that participants with GTS had higher error rates than controls, and their responses were faster than those of controls in incompatible stimuli. Our findings provide novel evidence of a key difference between youngsters with GTS and typically developing participants in the ability to effectively control the production of own motor responses to sensory inputs deriving from observed actions.

Right Temporoparietal Junction Plays a Role in the Modulation of Emotional Mimicry by Group Membership

Our prior research demonstrated that the right temporoparietal junction (rTPJ) exerted a modulatory role in ingroup bias in emotional mimicry. In this study, two experiments were conducted to further explore whether the rTPJ is a neural region for emotional mimicry or for the modulation of emotional mimicry by group membership in a sham-controlled, double-blinded, between-subject design. Both experiments employed non-invasive transcranial direct current stimulation (tDCS) to temporarily change the cortical excitability over the rTPJ and facial electromyography (fEMG) to measure facial muscle activations as an index of emotional mimicry. After the anodal or sham stimulation, participants in Experiment 1 passively viewed a series of happy clips, while participants in Experiment 2 viewed happy clips performed by ethnic ingroup and outgroup models. fEMG analyses revealed that participants in Experiment 1 showed the same degree of happy mimicry for both tDCS conditions (anodal vs. sham) and participants in Experiment 2 showed an ingroup bias in happy mimicry in the sham condition, which disappeared in the anodal condition. Taken together, the present study demonstrated that rTPJ plays a role in the modulation of emotional mimicry by group membership.

Social identity and contamination: Young children are more willing to eat native contaminated foods

Ingesting dangerous substances can lead to illness, or even death, meaning that it is critical for humans to learn how to avoid potentially dangerous foods. However, young children are notoriously bad at choosing foods; they are willing to put nonfoods and disgust elicitors into their mouths. Because food choice is inherently social, we hypothesized that social learning and contamination might separately influence children's decisions about whether to eat or avoid a food. Here, we asked how children reason about foods that are contaminated by someone from within versus outside their culture. We presented 3- to 11-year-olds (N = 534) with videos of native and foreign speakers eating snacks. In Studies 1a and 1b, one speaker contaminated her food and the other did not, and we asked children (a) which food they would prefer to eat, (b) how germy each food was, and (c) which food would make them sick. Although children rated the contaminated food as germier regardless of whether it was contaminated by a foreign speaker (Study 1a) or by a native speaker (Study 1b), children were more likely to report that they would avoid eating foreign contaminated food compared with native contaminated food. In Study 2, we used a non-forced-choice method and found converging evidence that children attend to both culture and contamination when making food choices but that with age they place more weight on contamination status.

The effects of self-relevance vs. reward value on facial mimicry

Facial mimicry is a ubiquitous social behaviour modulated by a range of social cues, including those related to reward value and self-relevance. However, previous research has typically focused on a single moderator at a time, and it remains unknown how moderators interact when studied together. We compared the influence of reward value and self-relevance, by conditioning participants to associate certain faces with winning or losing money for themselves, or, with winning or losing money for another person. After conditioning, participants watched videos of these faces making happy and angry facial expressions whilst we recorded facial electromyographic activity. We found greater smile mimicry (activation of the Zygomaticus Major muscle) in response to happy expressions performed by faces associated with participants' own outcomes vs. faces associated with another person's outcomes. In contrast to previous research, whether a face was associated with winning or losing money did not modulate facial mimicry responses. These results, although preliminary, suggest that when faces are associated with both self-relevance and reward value, self-relevance could supersede the impact of reward value during facial mimicry.

Right Temporoparietal Junction Modulates In-Group Bias in Facial Emotional Mimicry: A tDCS Study

The present study employs transcranial direct current stimulation (tDCS), a non-invasive brain stimulation technique, to explore the possible role of the right temporoparietal junction (rTPJ) in regulating in-group bias in facial emotional mimicry. Participants received either anodal or cathodal stimulation, or they were assigned to a sham condition. After that, they passively viewed a series of video clips depicting different emotions (happiness and anger) that were performed either by ethnic in-group or out-group models. The emotion-specific muscle activities, zygomatic major (ZM) and corrugator supercilii (CS) were recorded simultaneously as the index of facial emotional mimicry. The results first confirm the in-group bias in facial emotional mimicry in the sham condition, as shown in prior studies, though it only occurs in happy mimicry. Moreover, the in-group bias in facial emotional mimicry is modulated by the cortical excitability over the rTPJ, which may be attributed to the accompanied change of overlap of the mental representations of in-group and out-group. This study provides a close look at the neural underpinning of the modulation of facial emotional mimicry by group membership and highlights the role of rTPJ in on-line control of co-activated self and other representations in social cognition.

Developmental trajectory of interpersonal motor alignment: Positive social effects and link to social cognition

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Interpersonal motor alignment (IMA) has positive effects on healthy social life.

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IMA - mimicry, synchrony, automatic imitation - is studied throughout development.

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It relies on motor resonance brain mechanisms identified throughout development.

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It is modulated by contextual and personal factors.

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IMA is underinvestigated in adolescence, yet it may aid to enhance resilience.

Interpersonal motor alignment is a ubiquitous behavior in daily social life. It is a building block for higher social cognition, including empathy and mentalizing and promotes positive social effects. It can be observed as mimicry, synchrony and automatic imitation, to name a few. These phenomena rely on motor resonance processes, i.e., a direct link between the perception of an action and its execution. While a considerable literature debates its underlying mechanisms and measurement methods, the question of how motor alignment comes about and changes in ontogeny all the way until adulthood, is rarely discussed specifically. In this review we will focus on the link between interpersonal motor alignment, positive social effects and social cognition in infants, children, and adolescents, demonstrating that this link is present early on in development. Yet, in reviewing the existing literature pertaining to social psychology and developmental social cognitive neuroscience, we identify a knowledge gap regarding the healthy developmental changes in interpersonal motor alignment especially in adolescence.

Becoming better together: The early development of interpersonal coordination

Crucial for interacting successfully with other people is the ability to coordinate one's actions with those of others. Interpersonal coordination can be planned or emergent (spontaneous). Although typically easy for adults, coordinating successfully and smoothly with others may be far from trivial for infants and toddlers. What do we know about the developmental trajectory of interpersonal coordination in the first years of life? Which processes play a role in successfully coordinating with others? And how does the development of interpersonal coordination impact other aspects of children's development? In this chapter, we review when and how infants and young children develop successful interpersonal coordination skills (planned and emergent) in early childhood. We argue that insights from the field of cognitive (neuro-) science have significantly advanced our knowledge on which social-cognitive processes underlie interpersonal coordination and its development. In particular, we discuss four important social-cognitive processes; monitoring and predicting others' actions as well as planning and controlling one's own actions. We then present findings on the impact of interpersonal coordination on young children's social understanding, their prosocial behavior and affiliation. Together, we conclude that for future research on the development of interpersonal coordination interdisciplinary exchanges between fields like cognitive (neuro-) science and developmental science offer promising avenues.

Observing third-party ostracism enhances facial mimicry in 30-month-olds

Mimicry is suggested to be one of the strategies via which we enhance social affiliation. Although recent studies have shown that, like adults, young children selectively mimic the facial actions of in-group over out-group members, it is unknown whether this early mimicry behavior is driven by affiliative motivations. Here we investigated the functional role of facial mimicry in early childhood by testing whether observing third-party ostracism, which has previously been shown to enhance children's affiliative behaviors, enhances facial mimicry in 30-month-olds. Toddlers were presented with videos in which one shape was ostracized by other shapes or with control videos that did not show any ostracism. Before and after this, the toddlers observed videos of models performing facial actions (e.g., eyebrow raising, mouth opening) while we measured activation over their corresponding facial muscles using electromyography (EMG) to obtain an index of facial mimicry. We also coded the videos of the sessions for overt imitation. We found that toddlers in the ostracism condition showed greater facial mimicry at posttest than toddlers in the control condition, as indicated by both EMG and behavioral coding measures. Although the exact mechanism underlying this result needs to be investigated in future studies, this finding is consistent with social affiliation accounts of mimicry and suggests that mimicry may play a key role in maintaining affiliative bonds when toddlers perceive the risk of social exclusion.

fNIRS for Tracking Brain Development in the Context of Global Health Projects

Over the past 25 years, functional near-infrared spectroscopy (fNIRS) has emerged as a valuable tool to study brain function, and it is in younger participants where it has found, arguably, its most successful application. Thanks to its infant-friendly features, the technology has helped shape research in the neurocognitive development field by contributing to our understanding of the neural underpinnings of sensory perception and socio-cognitive skills. Furthermore, it has provided avenues of exploration for markers of compromised brain development. Advances in fNIRS instrumentation and methods have enabled the next step in the evolution of its applications including the investigation of the effects of complex and interacting socio-economic and environmental adversities on brain development. To do this, it is necessary to take fNIRS out of well-resourced research labs (the majority located in high-income countries) to study at-risk populations in resource-poor settings in low- and middle-income countries (LMICs). Here we review the use of this technology in global health studies, we discuss the implementation of fNIRS studies in LMICs with a particular emphasis on the Brain Imaging for Global Health (BRIGHT) project, and we consider its potential in this emerging field.