The modulation of facial mimicry by attachment tendencies and their underlying affiliation motives in 3-year-olds: An EMG study

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.

No evidence for modulation of facial mimicry by attachment tendencies in adulthood: an EMG investigation

Mimicking another individual functions as a social glue: it smoothens the interaction and fosters affiliation. Here, we investigated whether the intrinsic motivation to affiliate with others, stemming from attachment relationships, modulates individuals' engagement in facial mimicry (FM). Participants (N = 100; MAge = 24.54 years, SDAge = 3.90 years) observed faces with happy, sad, and neutral expressions, while their facial muscle activity was recorded with electromyography. Attachment was measured with the Attachment Styles Questionnaire, which provides a multidimensional profile for preoccupied and dismissing styles. It was proposed that the preoccupied and dismissing styles are characterized by high and low intrinsic affiliation motivation, respectively, and these were hypothesized to manifest in enhanced and diminished FM. Participants showed happy and sad FM, yet attachment styles did not significantly predict FM. Bayes Factor analyses lend evidence favoring the null hypothesis, suggesting that adult attachment do not contribute to FM.

Influence of child and adult faces with face masks on emotion perception and facial mimicry

Emotional mimicry, the imitation of others' emotion expressions, is related to increased interpersonal closeness and better interaction quality. Yet, little research has focused on the effect of face masks on emotional mimicry and none on (masked) child faces. To address this gap, we conducted an online experiment (N = 235, German sample, adult perceivers). Masks reduced emotion recognition accuracy for all expressions, except in the case of anger in masked child faces, where perceived anger was even increased. Perceived interpersonal closeness was reduced for masked happy and sad faces. For both child and adult expressers, masks reduced facial mimicry of happy expressions, with no mask effects for sadness and anger expression. A stronger mask effect on facial happiness mimicry of child faces was mediated by the degree of emotion recognition accuracy. Smiles shown by masked children were not recognized well, likely due to the absence of wrinkles around the eyes in child faces. Independent of masks, sadness shown by children was mimicked even more strongly than when shown by adults. These results provide evidence for facial mimicry of child expressions by adult perceivers and show that the effects of face masks on emotion communication may vary when children wear them.

Applicability of a Novel Attunement Instrument and Its Relationship to Parental Sensitivity in Infants With and Without Visual Impairments

This study investigated the applicability of a novel instrument to assess parent–child attunement in free play interactions, in dyads with an infant with and without visual impairments (VI). We here report the findings on the reliability and applicability of the newly developed Attune & Stimulate Mother–Infant 56-items Instrument (A&S M-I) in two separate samples: one with infants with VI (N = 20) and one with typically sighted infants (N = 24). In addition, we assessed the contribution of parental sensitivity to attunement in dyadic interactions. The A&S M-I is an observational comprehensive instrument of behaviors that captures different body parts and their motility (i.e., finger movements, arm waving, and foot kicking), and different senses (i.e., audio, tactile, and visual). The appropriate responding of a parent to the child’s signal (i.e., matching and containing) reflects the ability to attune in the dyad as well as parent’s ability to stimulate the child to become engaged in the contact or activity. Consistency assessments revealed good reliability for maternal and infant behaviors, acceptable internal consistency and good test–retest reliability. Furthermore, both samples scored significantly above chance level on attunement, suggesting that the instrument captures parent–infant behavioral coordination, and VI was not related to parent–infant attunement. Lastly, a relation between parental sensitivity and attunement was found only in the TS sample. Altogether, these findings provide promising initial evidence of the applicability of the A&S M-I instrument for assessing dyadic attunement across different populations and ages. Having assessed the applicability of this observational instrument, future work should corroborate these findings in larger samples.

Eating in Synch: An investigation of parent-infant behaviour coordination during feeding interactions

During feeding, parents have been described to move their mouth as if they were eating themselves. Such matching of behaviours between parents and their infants during face-to-face interactions represents an example of behavioural synchrony. To date, however, the function of these synchronous eating-like mouth movements by the caregiver remains unexplored. To address this question, two competing hypotheses were tested: 1) the instructional hypothesis proposing that parents make eating-like mouth movements, such as opening and closing their mouth, to demonstrate to their infants what they need to do; 2) the mimicry hypothesis suggesting that parents imitate their infant's mouth actions to enhance affiliation. To test these hypotheses, we examined the temporal dependencies between parents' and infants' mouth movements. We reasoned that parents' mouth movements would occur before their infants' if they serve an instructional purpose, but that they would happen after, if parents mimic their infants. Additionally, we expected that parents' matching mouth movements would be more likely when their infants looked at them in both cases. To examine these hypotheses, fifteen caregivers were observed as they were feeding their six-month-old infants. Time-window sequential analysis was conducted to quantify how likely parents were to display mouth opening and closing before or after their infants did. The results revealed that parents' mouth movements were more likely to follow infants' movements and are thus in line with the mimicry hypothesis. Interestingly, these mouth movements of parents were independent of infant's gaze.

(Un)mask yourself! Effects of face masks on facial mimicry and emotion perception during the COVID-19 pandemic

Face masks have been said to impact face-to-face interaction negatively. Yet, there is limited evidence on the degree to which partial face occlusion is detrimental to empathic processes such as emotion perception and facial mimicry. To address this question, we conducted an online experiment (N=200, U.K. sample) that assessed subjective ratings and facial expressions (mimicry) in response to masked and unmasked faces. Perceivers were able to recognise happiness and sadness in dynamic emotion expressions independent of (surgical) face masks. However, perceived emotion intensity and interpersonal closeness were reduced for masked faces. Facial mimicry, the perceiver's imitation of the expresser's emotional display, was reduced or absent in response to happy but preserved for sad mask-covered expressions. For happy target expressions, the face-mimicry link was partially mediated by perceived emotion intensity, supporting the idea that mimicry is influenced by context effects. Thus, these findings suggest that whether face masks impede emotion communication depends on the emotion expressed and the emotion-communication aspect of interest. With unprecedented changes in nonverbal communication brought about by the COVID-19 pandemic, this research marks a first contribution to our understanding of facial mimicry as an important social regulator during these times.

Five-year-olds' facial mimicry following social ostracism is modulated by attachment security

Social ostracism triggers an increase in affiliative behaviours. One such behaviour is the rapid copying of others' facial expressions, called facial mimicry. Insofar, it remains unknown how individual differences in intrinsic affiliation motivation regulate responses to social ostracism during early development. We examined children's facial mimicry following ostracism as modulated by individual differences in the affiliation motivation, expressed in their attachment tendencies. Resistant and avoidant tendencies are characterized by high and low affiliation motivation, and were hypothesized to lead to facial mimicry enhancement or suppression towards an ostracizing partner, respectively. Following an ostracism manipulation in which children played a virtual game (Cyberball) with an includer and an excluder peer, mimicry of the two peers' happy and sad facial expressions was recorded with electromyography (EMG). Attachment was assessed via parent-report questionnaire. We found that 5-year-olds smiled to sad facial expressions of the excluder peer, while they showed no facial reactions for the includer peer. Neither resistant nor avoidant tendencies predicted facial mimicry to the excluder peer. Yet, securely attached children smiled towards the excluder peer, when sad facial expressions were displayed. In conclusion, these findings suggest a modulation of facial reactions following ostracism by early attachment.

The effect of eye gaze direction on emotional mimicry: A multimodal study with electromyography and electroencephalography

Emotional mimicry plays an important role in social interaction and is influenced by social context, especially eye gaze direction. However, the neural mechanism underlying the effect of eye gaze direction on emotional mimicry is unclear. Here, we explored how eye gaze direction influenced emotional mimicry with a combination of electromyography (EMG) and electroencephalography (EEG) techniques, which may provide a more comprehensive measure. To do this, we recorded facial EMG and scalp EEG signals simultaneously while participants observed emotional faces (happy vs. angry) with direct or averted gaze. Then, we split the EEG trials into two mimicry intensity categories (high mimicry intensity, HMI vs. low mimicry intensity, LMI) according to EMG activity. The ERP difference between HMI and LMI EEG trials revealed four ERP components (P50, P150, N200 and P300), and the effect of eye gaze direction on emotional mimicry was prominent on P300 at P7 and P8. Moreover, we also observed differences in the effect of eye gaze direction on mimicry of happy faces and angry faces, which were found on P300 at P7, as well as P150 at P7 and N200 at P7 and Pz. In short, the present study isolated the neural signals of emotional mimicry with a new multimodal method, and provided empirical neural evidence that eye gaze direction affected emotional mimicry.

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.

Correction: The modulation of facial mimicry by attachment tendencies and their underlying affiliation motives in 3-year-olds: An EMG study

[This corrects the article DOI: 10.1371/journal.pone.0218676.].