Fourteen-month-old infants use interpersonal synchrony as a cue to direct helpfulness

Comparison of speech and music input in North American infants' home environment over the first 2 years of life

Infants are immersed in a world of sounds from the moment their auditory system becomes functional, and experience with the auditory world shapes how their brain processes sounds in their environment. Across cultures, speech and music are two dominant auditory signals in infants' daily lives. Decades of research have repeatedly shown that both quantity and quality of speech input play critical roles in infant language development. Less is known about the music input infants receive in their environment. This study is the first to compare music input to speech input across infancy by analyzing a longitudinal dataset of daylong audio recordings collected in English-learning infants' home environments, at 6, 10, 14, 18, and 24 months of age. Using a crowdsourcing approach, 643 naïve listeners annotated 12,000 short snippets (10 s) randomly sampled from the recordings using Zooniverse, an online citizen-science platform. Results show that infants overall receive significantly more speech input than music input and the gap widens as the infants get older. At every age point, infants were exposed to more music from an electronic device than an in-person source; this pattern was reversed for speech. The percentage of input intended for infants remained the same over time for music while that percentage significantly increased for speech. We propose possible explanations for the limited music input compared to speech input observed in the present (North American) dataset and discuss future directions. We also discuss the opportunities and caveats in using a crowdsourcing approach to analyze large audio datasets. A video abstract of this article can be viewed at https://youtu.be/lFj_sEaBMN4 RESEARCH HIGHLIGHTS: This study is the first to compare music input to speech input in infants' natural home environment across infancy. We utilized a crowdsourcing approach to annotate a longitudinal dataset of daylong audio recordings collected in North American home environments. Our main results show that infants overall receive significantly more speech input than music input. This gap widens as the infants get older. Our results also showed that the music input was largely from electronic devices and not intended for the infants, a pattern opposite to speech input.

Effects of two-person synchronized cycling exercise on interpersonal cooperation: A near-infrared spectroscopy hyperscanning study

Objective

Although psychological research indicating the synchronous activities can promote interpersonal cooperation, thus far there is no direct evidence that two-person synchronous exercise effectively enhances interpersonal cooperative behaviors in Physical exercise field. This suggests that, although synchronization phenomenon is widespread in sports and is considered a potential tool for enhancing teamwork, its specific effects and functioning mechanisms still need to be clarified by further scientific research. This study intends to use two-person synchronized cycling exercise to investigate the synchronized exercise effect on interpersonal cooperative behavior and its underlying neural mechanisms.

Methods

Eighty college students without regular exercise habits will be randomly assigned to the experimental group (10 male dyads and 10 female dyads) and the control group (10 male dyads and 10 female dyads). During the experiment, dyads in the experimental group performed a 30-minute synchronized cycling exercise with synchronized pedaling movements; dyads in the control group rested sedentary in the same environment for 30 minutes. Interpersonal cooperative behavior was assessed with the Prisoner's Dilemma task, and the interpersonal neural synchronization(INS) data were collected in the prefrontal cortex using near-infrared hyperscanning.

Results

This study compared behavior and brain activity before and after synchronous exercise. Behavioral results revealed that, compared to pre-exercise, dyads in the post-exercise had higher average cooperation rates, higher cooperation efficiency and shorter cooperation response times. Compared to post-sedentary, dyads in the post-exercise had shorter cooperation response times and higher cooperation efficiency. Furthermore, brain data showed that,compared to pre-exercise, dyads in the post-exercise had stronger INS in the dorsolateral prefrontal cortex(DLPFC), whereas the dyads in the post-exercise had stronge INS in the DLPFC compared to post-sedentary. After controlling for dyads' anxiety and mood states, this study also found a marginally significant negative correlation between INS differences in the left DLPFC and cooperation response time differences.

Conclusions

This research confirms, from both behavioral and neuroscience perspectives, that one synchronization cycle can significantly enhance interpersonal cooperative behavior, and this positive effect is closely associated with increased INS in the left DLPFC. This study provides new insights into understanding how positive interactive exercises promote interpersonal cooperation through specific neural mechanisms.

Development strategy of early childhood music education industry: An IFS-AHP-SWOT analysis based on dynamic social network

Early childhood music education has garnered recognition for its unique contribution to cognitive, emotional, and social development in children. Nevertheless, the industry grapples with numerous challenges, including a struggle to adapt traditional educational paradigms to new curriculum reforms, and an excessive emphasis on skill training at the expense of nurturing a love for music and aesthetics in children. To navigate these challenges and explore growth strategies for the early childhood music education industry, we initiated a comprehensive approach that involved distributing surveys to practitioners and parents and engaging experts for insightful discussions. Consequently, we proposed an analytical method based on dynamic social networks in conjunction with Intuitionistic Fuzzy Sets (IFS), Analytic Hierarchy Process (AHP), and Strengths, Weaknesses, Opportunities, and Threats (SWOT) analysis, collectively referred to as IFS-AHP-SWOT. This integrated methodology synergizes the capabilities of dynamic social networks, IFS, AHP, and SWOT analysis to offer a nuanced perspective on industry development strategies. The findings underscore that institutions within the early childhood music education industry need to adopt a development strategy that leverages their strengths and opportunities to foster sustainable growth. Ultimately, this research aims to provide critical decision-making support for industry practitioners, policymakers, and researchers, contributing significantly to the ongoing discourse on strategic development in the early childhood music education industry.

Biological principles for music and mental health

Efforts to integrate music into healthcare systems and wellness practices are accelerating but the biological foundations supporting these initiatives remain underappreciated. As a result, music-based interventions are often sidelined in medicine. Here, I bring together advances in music research from neuroscience, psychology, and psychiatry to bridge music's specific foundations in human biology with its specific therapeutic applications. The framework I propose organizes the neurophysiological effects of music around four core elements of human musicality: tonality, rhythm, reward, and sociality. For each, I review key concepts, biological bases, and evidence of clinical benefits. Within this framework, I outline a strategy to increase music's impact on health based on standardizing treatments and their alignment with individual differences in responsivity to these musical elements. I propose that an integrated biological understanding of human musicality-describing each element's functional origins, development, phylogeny, and neural bases-is critical to advancing rational applications of music in mental health and wellness.

Early social communication through music: State of the art and future perspectives

A growing body of research shows that the universal capacity for music perception and production emerges early in development. Possibly building on this predisposition, caregivers around the world often communicate with infants using songs or speech entailing song-like characteristics. This suggests that music might be one of the earliest developing and most accessible forms of interpersonal communication, providing a platform for studying early communicative behavior. However, little research has examined music in truly communicative contexts. The current work aims to facilitate the development of experimental approaches that rely on dynamic and naturalistic social interactions. We first review two longstanding lines of research that examine musical interactions by focusing either on the caregiver or the infant. These include defining the acoustic and non-acoustic features that characterize infant-directed (ID) music, as well as behavioral and neurophysiological research examining infants' processing of musical timing and pitch. Next, we review recent studies looking at early musical interactions holistically. This research focuses on how caregivers and infants interact using music to achieve co-regulation, mutual engagement, and increase affiliation and prosocial behavior. We conclude by discussing methodological, technological, and analytical advances that might empower a comprehensive study of musical communication in early childhood.

Musical engagement as a duet of tight synchrony and loose interpretability

Joint engagement in music often facilitates positive social interaction, effectively shifting participants' perspective from the individual to the collective. The result is tight coordination and uniformity between participants, but at the same time, also remarkable flexibility and creativity. How does music achieve such a fine balance between the strict alignment necessary for coordination, and the substantial latitude necessary for experimentation? To address this question, I propose to analyze joint music engagement within the tight-loose theoretical framework broadly used in the social sciences. Tight-loose theory was originally developed for distinguishing between two archetypical cultural tendencies. On the one hand, tightness, which denotes stringent adherence to social norms, and on the other hand, looseness, which refers to a more flexible and less restrictive attitude towards norms. I posit that the flexible form of collaboration characteristic of musical interaction is due to a coexistence of tightness and looseness within joint engagement in music. I argue that the tight aspects of music can be attributed to its rhythmic structure, which requires continuous and precise temporal alignment between participants. Indeed, when experienced on its own, outside of a musical context, interpersonal synchrony has been repeatedly shown to enhance diverse positive social capacities such as bonding, collaboration and affiliation between interacting individuals, but at the expense of increasing conformity, blind obedience and even hostility towards non-group members. These effects are consistent with synchrony driving a tight interaction, inducing a sense of common group membership (CGM), which can endow music with necessary rigor and order. In contrast, the loose side of music may pertain to the ambiguity in meaning and intention expressed by music, which leaves ample room for interpretation and improvisation. I thus propose that the combined tight-loose nature of music, can simultaneously enhance positive social behaviors and reduce negative ones, leading to a tolerant form of group membership (TGM).

Judgment of togetherness in performances by musical duos

Musicians experience varying degrees of togetherness with their co-performers when playing in ensembles. However, little is known about how togetherness is experienced by audiences and how interpersonal dynamics in body motion and sound support the judgment of togetherness. This research investigates audience sensitivity to audio and visual markers of interperformer coordination and expressivity in ensembles, in relation to modality of stimulus presentation and audience music background. A set of duo ensemble performances, comprising motion capture recordings of the musicians' upper bodies and instruments, were presented to participants with varying music background, including novices and semi-professional musicians. Participants were required to: (i) watch and listen, (ii) only watch, and (iii) only listen to the selected recordings, whilst providing dynamic ratings of how much togetherness between musicians they perceived. Results demonstrate that sound intensity and similarity in right arm motion (quantified using cross-wavelet transform analysis) were significant predictors of rated togetherness in novices, whilst sound synchronization and chest motion coordination predicted togetherness responses in semi-professional musicians. These results suggest the relevance of the quality of body motion coordination and of certain features of the audio outputs in the audience perception of togetherness. This research contributes to a better understanding of the perceptual mechanisms supporting socio-cognitive judgments of joint action activities.

Higher empathy is associated with stronger social bonding when moving together with music

Empathy-understanding and sharing the feelings and experiences of others-is one of our most important social capacities. Music is a social stimulus in that it involves communication of mental states, imitation of behavior, and synchronization of movements. As empathy and music are so closely linked, we investigated whether higher empathy is associated with stronger social bonding in interpersonal interactions that feature music. In two studies, participants watched videos in which we manipulated interpersonal synchrony between the movements of a virtual self and a virtual other person during walking with instrumental music or a metronome. In both studies, temporally aligned movements increased social bonding with the virtual other and higher empathy was associated with increased social bonding in movement interactions that featured music. Additionally, in Study 1, participants with lower empathy felt more connected when interacting with a metronome compared to music. In Study 2, higher trait empathy was associated with strong increases of social bonding when interacting with a temporally aligned virtual other, but only weak increases of social bonding with a temporally misaligned virtual other. These findings suggest that empathy plays a multifaceted role in how we enjoy, interpret, and use music in social situations.

Synchrony During Online Encounters Affects Social Affiliation and Theory of Mind but Not Empathy

Moving together in time affects human social affiliation and cognition. However, it is unclear whether these effects hold for on-line video meetings and whether they extend to empathy (understanding or sharing others' emotions) and theory of mind (ToM; attribution of mental states to others). 126 young adult participants met through online video in unacquainted pairs. Participants either performed 3 min of synchronous arm movements paced by sounds (n = 40), asynchronous movements (n = 46) or a small talk condition (n = 40). In a subsequent empathy task, participants engaged in a conversation. A video recording of this conversation was played back, and each participant rated, at predetermined time points, how they felt and how they thought their partner felt. From this we calculated empathic accuracy (accuracy of the estimation of the other's emotions) and emotional congruence (emotion sharing). ToM was measured by showing videos of geometrical shapes interacting and asking the participants to describe what happened, measuring the amount of intentionality. We found that participants in the synchrony condition rated feeling greater closeness and similarity to their partners relative to the asynchronous condition. Further, participants in the synchrony group tended to ascribe more intentionality to the abstract shapes than participants in asynchrony condition, suggesting greater ToM. Synchrony and asynchrony groups did not reliably differ in empathic accuracy nor emotional congruence. These results suggest that moving in synchrony has effects on social affiliation measures even in online encounters. These effects extend to ToM tendencies but not empathic accuracy or emotion sharing. These results highlight the potential of synchronous movement in online encounters to affect a subset of social cognition and affiliation measures.

The Groove Enhancement Machine (GEM): A Multi-Person Adaptive Metronome to Manipulate Sensorimotor Synchronization and Subjective Enjoyment

Synchronization of movement enhances cooperation and trust between people. However, the degree to which individuals can synchronize with each other depends on their ability to perceive the timing of others’ actions and produce movements accordingly. Here, we introduce an assistive device—a multi-person adaptive metronome—to facilitate synchronization abilities. The adaptive metronome is implemented on Arduino Uno circuit boards, allowing for negligible temporal latency between tapper input and adaptive sonic output. Across five experiments—two single-tapper, and three group (four tapper) experiments, we analyzed the effects of metronome adaptivity (percent correction based on the immediately preceding tap-metronome asynchrony) and auditory feedback on tapping performance and subjective ratings. In all experiments, tapper synchronization with the metronome was significantly enhanced with 25–50% adaptivity, compared to no adaptation. In group experiments with auditory feedback, synchrony remained enhanced even at 70–100% adaptivity; without feedback, synchrony at these high adaptivity levels returned to near baseline. Subjective ratings of being in the groove, in synchrony with the metronome, in synchrony with others, liking the task, and difficulty all reduced to one latent factor, which we termed enjoyment. This same factor structure replicated across all experiments. In predicting enjoyment, we found an interaction between auditory feedback and metronome adaptivity, with increased enjoyment at optimal levels of adaptivity only with auditory feedback and a severe decrease in enjoyment at higher levels of adaptivity, especially without feedback. Exploratory analyses relating person-level variables to tapping performance showed that musical sophistication and trait sadness contributed to the degree to which an individual differed in tapping stability from the group. Nonetheless, individuals and groups benefitted from adaptivity, regardless of their musical sophistication. Further, individuals who tapped less variably than the group (which only occurred ∼25% of the time) were more likely to feel “in the groove.” Overall, this work replicates previous single person adaptive metronome studies and extends them to group contexts, thereby contributing to our understanding of the temporal, auditory, psychological, and personal factors underlying interpersonal synchrony and subjective enjoyment during sensorimotor interaction. Further, it provides an open-source tool for studying such factors in a controlled way.

The intrapersonal and interpersonal consequences of interpersonal synchrony

Interpersonal synchrony, the time-matching behaviors, is pervasive in human interactions. This resonation of movements or other forms was generally considered as one of critical survival skills for humans, as the important consequences of synchronizing with other persons in review of the empirical data in this article. These include positive affects towards and between interacting partners, but also include complex effects on the individual level. The intrapersonal effects of interpersonal synchrony are varied with positive or negative ones, including cognitive style, attitude bias, mood state, self-regulatory ability, and academic performance. At the interpersonal level, synchronized movement consistently affects the interaction with the partner and his/her affiliations, but they can be eliminated or magnified by several moderators, such as physiological arousal, shared intentionality, group bias, and musical rhythm. Finally, the research discussed the possible mechanisms underlying the effects of interpersonal synchrony in psychological and biological aspects.

Employees’ Belief in a Just World and Sustainable Organizational Citizenship Behaviors: The Moderating Effect of Interpersonal Intelligence

To both survive and develop continuously, enterprises must overcome many kinds of competition and challenges. Cultivating employees’ active and sustainable organizational citizenship behavior is important for enterprises to successfully cope with turbulence and uncertain events during their development. Building on social exchange theory, this study proposes a theoretical framework. In this framework, belief in a just world has a certain predictive effect on organizational citizenship behavior, and this effect is affected by interpersonal intelligence. In this study, we investigated the development level of and factors influencing employees’ organizational citizenship behavior in current organizations. This research adopted the empirical research method of a questionnaire survey, and investigated 230 employees from 15 different enterprises by using the Belief in a Just World Scale, Organizational Citizenship Behavior Scale, and Interpersonal Intelligence Scale. After excluding the questionnaires that did not meet the requirements, a total of 193 valid questionnaires were obtained. To estimate the proposed relationships in the conceptual model, we analyzed the data through SPSS-21. The results showed that belief in a just world, interpersonal intelligence, and organizational citizenship behavior were significantly positively correlated. Interpersonal intelligence played a moderating role between belief in a just world and organizational citizenship behavior; the belief in a just world of individuals with high interpersonal intelligence had a more significant positive predictive effect on organizational citizenship behavior. This meant that under a certain level of belief in a just world, a high level of interpersonal intelligence was more conducive to promoting employees’ sustainable organizational citizenship behavior.

Can Dance and Music Make the Transition to a Sustainable Society More Feasible?

Transition to sustainability is a process that requires change on all levels of society from the physical to the psychological. This review takes an interdisciplinary view of the landscapes of research that contribute to the development of pro-social behaviors that align with sustainability goals, or what we call 'inner sustainability'. Engaging in musical and dance activities can make people feel trust and connectedness, promote prosocial behavior within a group, and also reduce prejudices between groups. Sustained engagement in these art forms brings change in a matter of seconds (such as hormonal changes and associated stress relief), months (such as improved emotional wellbeing and learning outcomes), and decades (such as structural changes to the brains of musicians and dancers and superior skills in expressing and understanding emotion). In this review, we bridge the often-separate domains of the arts and sciences by presenting evidence that suggests music and dance promote self-awareness, learning, care for others and wellbeing at individual and group levels. In doing so, we argue that artistic practices have a key role to play in leading the transformations necessary for a sustainable society. We require a movement of action that provides dance and music within a constructive framework for stimulating social sustainability.

Language and Movement Synchronization in Dyadic Psychotherapeutic Interaction - A Qualitative Review and a Proposal for a Classification

In individual psychotherapy verbal communication and movement synchronization are closely interrelated. The microanalysis of timing, rhythm and gestalt of movement has established dynamic movement coordination as a systemic property of the dyadic interaction. Movement synchronization supports and enhances the unfolding of linguistic meaning. In order to substantiate the importance of the concept of synchrony for adult psychotherapy we review evidence from developmental psychology and discuss approaches to measure synchrony with particular reference to the naturalistic setting of dyadic psychotherapy. As the concept of synchrony is still ambiguous, and the respective interactional phenomena are ephemeral and fluid, in the current paper we suggest a set of five criteria for the description of synchronization in general terms and eight additional criteria which specifically enable the description of phenomena of movement synchronization. The five general dimensions are: (1) context, (2) modality, (3) resources, (4) entrainment, and (5) time-lag. The eight categories for the description of movement synchrony are: (1) spatial direction, (2) amplitude, (3) sinuosity, (4) duration, (5) event structure, (6) phase, (7) frequency, and (8) content. To understand the process of participatory sense-making and the emergence of meaning in psychotherapy, synchrony research has to cope with the multimodality of the embodied interaction. This requires an integrated perspective of movement and language. A system for the classification of synchrony phenomena may contribute to the linking of variations and patterns of movement with language and linguistic utterances.

A syncing feeling: reductions in physiological arousal in response to observed social synchrony

Synchronized movements are often key elements in activities where social bonding and emotional connection are a shared goal, such as religious gatherings, sporting events, parties and weddings. Previous studies have shown that synchronous movements enhance prosocial attitudes and affiliative behaviors. Similarly, observers attribute more social closeness to people moving synchronously together than people moving asynchronously. The mechanisms by which synchrony modulates these attributions are not well understood. In the present study, we ask whether viewing synchronous activities influences physiological arousal as measured by skin conductance and whether group size impacts this effect. Undergraduates viewed a series of short videos depicting people moving either (1) in or out of synchrony with each other and (2) in a large or small group. Participants’ skin conductance was measured. Change in skin conductance levels and response counts were attenuated while watching synchronous movement, but only in the large-group condition. Post-hoc analyses suggest that viewer enjoyment/interest in the large-group synchronous videos mediated this association for phasic skin conductance responses, but no evidence of mediation was found for tonic skin conductance levels. Results extend previous research on affiliative effects of first-person interpersonal synchrony and demonstrate that watching others moving synchronously has an attenuating effect on observers’ physiological state.

Interpersonal Coordination in Schizophrenia: A Scoping Review of the Literature

Interpersonal coordination forms the natural bridge between the self and others. It arises from the dynamic and complex set of embodied processes that involve nonverbal behaviors, perceptions, movement, and emotions that support adaptive interactions. Disembodiment has been implicated in a myriad of core clinical phenomena that manifest in a "praecox feeling" in persons with schizophrenia during interpersonal interactions. To further understand mechanisms underlying aberrant interpersonal interactions in schizophrenia, recent research has focused on mimicry, imitation, and interactional synchrony. In this study, we conducted a Pubmed, Web of Science, and PsycInfo database review of the literature on interpersonal coordination in schizophrenia to evaluate the body of work in mimicry, imitation, and interactional synchrony in relation to schizophrenia-spectrum conditions. The results of the review suggest that the sensory-motor processes underlying interpersonal coordination may result in impaired abilities to mimic and synchronize nonverbal behavior during interactions. Opportunities for future progress lie in studies of interpersonal coordination at different developmental stages of psychosis, potential use of interpersonal coordination to improve treatment adherence and reduce stigma, as well as interventions to improve social functioning in people with a serious mental illness.

Creating a Compassionate World: Addressing the Conflicts Between Sharing and Caring Versus Controlling and Holding Evolved Strategies

For thousands of years, various spiritual traditions and social activists have appealed to humans to adopt compassionate ways of living to address the suffering of life. Yet, along with our potential for compassion and self-sacrifice, the last few thousand years of wars, slavery, tortures, and holocausts have shown humans can be extraordinarily selfish, callous, vicious, and cruel. While there has been considerable engagement with these issues, particularly in the area of moral psychology and ethics, this paper explores an evolutionary analysis relating to evolved resource-regulation strategies that can be called "care and share" versus "control and hold." Control and hold are typical of primates that operate through intimidatory social hierarchies. Care and share are less common in non-human primates, but evolved radically in humans during our hunter-gatherer stage when our ancestors lived in relatively interdependent, small, mobile groups. In these groups, individualistic, self-focus, and self-promoting control and hold strategies (trying to secure and accumulate more than others) were shunned and shamed. These caring and sharing hunter-gatherer lifestyles also created the social contexts for the evolution of new forms of childcare and complex human competencies for language, reasoning, planning, empathy, and self-awareness. As a result of our new 'intelligence', our ancestors developed agriculture that reduced mobility, increased group size, resource availability and storage, and resource competition. These re-introduced competing for, rather than sharing of, resources and advantaged those who now pursue (often aggressively) control and hold strategies. Many of our most typical forms of oppressive and anti-compassionate behavior are the result of these strategies. Rather than (just) thinking about individuals competing with one another, we can also consider these different resource regulation strategies as competing within populations shaping psychophysiological patterns; both wealth and poverty change the brain. One of the challenges to creating a more compassionate society is to find ways to create the social and economic conditions that regulate control and hold strategies and promote care and share. No easy task.

Dance on the Brain: Enhancing Intra- and Inter-Brain Synchrony

Dance has traditionally been viewed from a Eurocentric perspective as a mode of self-expression that involves the human body moving through space, performed for the purposes of art, and viewed by an audience. In this Hypothesis and Theory article, we synthesize findings from anthropology, sociology, psychology, dance pedagogy, and neuroscience to propose The Synchronicity Hypothesis of Dance, which states that humans dance to enhance both intra- and inter-brain synchrony. We outline a neurocentric definition of dance, which suggests that dance involves neurobehavioral processes in seven distinct areas including sensory, motor, cognitive, social, emotional, rhythmic, and creative. We explore The Synchronicity Hypothesis of Dance through several avenues. First, we examine evolutionary theories of dance, which suggest that dance drives interpersonal coordination. Second, we examine fundamental movement patterns, which emerge throughout development and are omnipresent across cultures of the world. Third, we examine how each of the seven neurobehaviors increases intra- and inter-brain synchrony. Fourth, we examine the neuroimaging literature on dance to identify the brain regions most involved in and affected by dance. The findings presented here support our hypothesis that we engage in dance for the purpose of intrinsic reward, which as a result of dance-induced increases in neural synchrony, leads to enhanced interpersonal coordination. This hypothesis suggests that dance may be helpful to repattern oscillatory activity, leading to clinical improvements in autism spectrum disorder and other disorders with oscillatory activity impairments. Finally, we offer suggestions for future directions and discuss the idea that our consciousness can be redefined not just as an individual process but as a shared experience that we can positively influence by dancing together.

Infant-adult synchrony in spontaneous and nonspontaneous interactions

Infant-adult synchrony has been reported through observational and experimental studies. Nevertheless, synchrony is addressed differently in both cases. While observational studies measure synchrony in spontaneous infant-adult interactions, experimental studies manipulate it, inducing nonspontaneous synchronous and asynchronous interactions. A still unsolved question is to what extent differ spontaneous synchrony from the nonspontaneous one, experimentally elicited. To address this question, we conducted a study to compare synchrony in both interactional contexts. Forty-three 14-month-old infants were randomly assigned to one of two independent groups: (1) the spontaneous interaction context, consisting of a storytime session; and (2) the nonspontaneous interaction context, where an assistant bounced the infant in synchrony with a stranger. We employed an optical motion capture system to accurately track the time and form of synchrony in both contexts. Our findings indicate that synchrony arising in spontaneous exchanges has different traits than synchrony produced in a nonspontaneous interplay. The evidence presented here offers new insights for rethinking the study of infant-adult synchrony and its consequences on child development.

The cultural evolutionary trade-off of ritualistic synchrony

From Australia to the Arctic, human groups engage in synchronous behaviour during communal rituals. Because ritualistic synchrony is widespread, many argue that it is functional for human groups, encouraging large-scale cooperation and group cohesion. Here, we offer a more nuanced perspective on synchrony's function. We review research on synchrony's prosocial effects, but also discuss synchrony's antisocial effects such as encouraging group conflict, decreasing group creativity and increasing harmful obedience. We further argue that a tightness-looseness (TL) framework helps to explain this trade-off and generates new predictions for how ritualistic synchrony should evolve over time, where it should be most prevalent, and how it should affect group well-being. We close by arguing that synthesizing the literature on TL with the literature on synchrony has promise for understanding synchrony's role in a broader cultural evolutionary framework. This article is part of the theme issue 'Ritual renaissance: new insights into the most human of behaviours'.

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.

Cultural Familiarity and Individual Musical Taste Differently Affect Social Bonding when Moving to Music

Social bonds are essential for our health and well-being. Music provides a unique and implicit context for social bonding by introducing temporal and affective frameworks, which facilitate movement synchronization and increase affiliation. How these frameworks are modulated by cultural familiarity and individual musical preferences remain open questions. In three experiments, we operationalized the affective aspects of social interactions as ratings of interpersonal closeness between two walking stick-figures in a video. These figures represented a virtual self and a virtual other person. The temporal aspects of social interactions were manipulated by movement synchrony: while the virtual self always moved in time with the beat of instrumental music, the virtual other moved either synchronously or asynchronously. When the context-providing music was more enjoyed, social closeness increased strongly with a synchronized virtual other, but only weakly with an asynchronized virtual other. When the music was more familiar, social closeness was higher independent of movement synchrony. We conclude that the social context provided by music can strengthen interpersonal closeness by increasing temporal and affective self-other overlaps. Individual musical preferences might be more relevant for the influence of movement synchrony on social bonding than musical familiarity.

Measuring Dynamics of Infant-Adult Synchrony Through Mocap

The temporal dynamics of parent-infant synchrony have been well documented. In recent years, the introduction of more accurate technologies for tracking movements has allowed the distinction of different morphological patterns of dyadic coordination. However, the potential of these technologies to explore infant-adult synchrony has not yet been explored. In the present study, we examined the temporal, spatial, and morphological synchrony patterns of infant-unknown adult pairs participating in a storytime session by a motion capture system (mocap). We find low but significant correlation levels of body synchrony between infants and unknown adults. This synchronized coactivity adopted two differentiated forms: mirror-like and anatomical. While the infants' movements mirrored those of the adults with a lag (0.9 s), the adults' reactions to the infants were anatomical with delay (0.4 s). This evidence could contribute novel insights to rethink synchrony and its measurement.

Rhythmic Training Improves Temporal Anticipation and Adaptation Abilities in Children With Hearing Loss During Verbal Interaction

Purpose In this study, we investigate temporal adaptation capacities of children with normal hearing and children with cochlear implants and/or hearing aids during verbal exchange. We also address the question of the efficiency of a rhythmic training on temporal adaptation during speech interaction in children with hearing loss. Method We recorded electroencephalogram data in children while they named pictures delivered on a screen, in alternation with a virtual partner. We manipulated the virtual partner's speech rate (fast vs. slow) and the regularity of alternation (regular vs. irregular). The group of children with normal hearing was tested once, and the group of children with hearing loss was tested twice: once after 30 min of auditory training and once after 30 min of rhythmic training. Results Both groups of children adjusted their speech rate to that of the virtual partner and were sensitive to the regularity of alternation with a less accurate performance following irregular turns. Moreover, irregular turns elicited a negative event-related potential in both groups, showing a detection of temporal deviancy. Notably, the amplitude of this negative component positively correlated with accuracy in the alternation task. In children with hearing loss, the effect was more pronounced and long-lasting following rhythmic training compared with auditory training. Conclusion These results are discussed in terms of temporal adaptation abilities in speech interaction and suggest the use of rhythmic training to improve these skills of children with hearing loss.

I'll just watch: Do the pro-social effects of coordination really generalize to non-actors?

Moving in time together has been shown to cultivate pro-social effects in co-actors, such as cooperation and helping. But less is known about who these effects apply to - whether they are restricted only to co-actors, or whether they generalize to those not involved in the coordination. One difference between past work finding generalized vs. restricted effects is whether these "outsiders" were present for the coordination or not. The present study explores whether the pro-social effects of coordination are seen towards observers as well as co-actors, and whether the absence or presence of observers during the coordination is a determining factor. Results show that greater cooperation following coordination is only seen amongst co- actors, regardless of whether the observers were present during the task or not. Findings are discussed in the context of the literature and alternative explanations for research showing generalized effects are suggested.

The Social Origins of Human Prosociality

From early in life, children help, comfort, and share with others. Recent research has deepened scientific understanding of the development of prosociality - efforts to promote the welfare of others. This article discusses two key insights about the emergence and early development of prosocial behavior, focusing on the development of helping. First, children's motivations and capabilities for helping change in quality as well as quantity over the opening years of life. Specifically, helping begins in participatory activities without prosocial intent in the first year of life, becoming increasingly autonomous and motivated by prosocial intent over the second year. Second, helping emerges through bidirectional social interactions, starting at birth, in which caregivers and others support the development of helping in a variety of ways and young children play active roles, often influencing caregiver behavior. The question now is not whether, but how social interactions contribute to the development of prosocial behavior. Recent methodological and theoretical advances provide exciting avenues for future research on the social and emotional origins of human prosociality.

Temporal predictability promotes prosocial behavior in 5-year-old children

Although interpersonal coordinative activities have been shown to produce prosocial effects in both adults and children, the underlying mechanisms remain unclear. While most approaches focus on the effect of mimicry and synchronous behavioral matching, we hypothesize that temporal predictability might play a central role in producing prosocial effects, as it directs coordination and might therefore strengthen shared intentionality. In a percussion task with pairs of 5-year old children, we manipulated temporal predictability and movement similarity/predictability between the pair’s movements. Temporal predictability was manipulated by instructing the pair to play the instruments either to beats that were evenly-spaced, and therefore predictable, or to beats that were random, and therefore unpredictable. Movement similarity/predictability was manipulated by having the pair play rhythmic patterns that were similar, predictable, or independent from each other. Children who played to predictable beats were more willing to solve problems cooperatively with their partners and to help when their partners had an accident. In contrast, there was no positive effect of rhythmic predictability or similarity. These results are the first to show that temporal predictability affects prosociality independent of movement similarity or predictability. We conclude that the predictable time frame commonly seen in coordinative activities may be key to strengthening shared intentionality and producing prosocial effects.

Accent Stabilizes 1:2 Sensorimotor Synchronization of Rhythmic Knee Flexion-Extension Movement in Upright Stance

Numerous studies have shown the importance of metrical structure on beat perception and sensorimotor synchronization (SMS), which indicates why metrical structure has evolved as a widespread musical element. In the current study, we aimed to investigate the effect of metrical structure with or without accented sounds and the alignment of accent with flexion or extension movements on the stability of 1:2 SMS in rhythmic knee flexion-extension movement in upright stance (flexing the knee once every two sounds). Fourteen participants completed 1:2 rhythmic knee flexion-extension movements with a metronome beat that accelerated from 2 to 8 Hz (the frequency of the movement was 1–4 Hz). Three sound-movement conditions were provided: (1) combining the flexion phase with loud (accented) sound and the extension phase with soft (non-accented) sound, (2) the reverse combination, and (3) combining both movements with loud sound. ANOVA results showed that metrical structure with accented sounds stabilizes 1:2 SMS in the range of 3.5–7.8 Hz in terms of timing accuracy, and flexing on the accented sound is more globally stable (resistant to phase transition) than flexing on the non-accented sound. Furthermore, our results showed that metrical structure with accented sounds induces larger movement amplitude in the range of 4.6–7.8 Hz than does that without accented sounds. The present study demonstrated that metrical structure with accented sounds stabilizes SMS and induces larger movement amplitude in rhythmic knee flexion-extension movement in upright stance than does SMS with sequences without accents. In addition, we demonstrated that coordinating flexion movement with accented sound is more globally stable than coordinating extension movement with accented sound. Thus, whereas previous studies have revealed that metrical structure enhances the timing accuracy of SMS, the current study revealed that metrical structure enhances the global stability of SMS.

Pet dogs exhibit social preference for people who synchronize with them: what does it tell us about the evolution of behavioral synchronization?

Humans show greater affiliation with people who are behaviorally synchronized with them but little is known about the impact of synchronization at an interspecific level. We, therefore, explored whether the synchronization of humans with dogs affects dogs' human preferences. Pet dogs were exposed to two unfamiliar persons: one synchronized her walking behavior with them and one walked randomly. In a preference test, molossoids exhibited a clear social preference for the synchronized person, unlike shepherds. We conclude that pet dogs show a greater affiliation with humans who mimic their walking behavior, although genetic selection modulates this propensity. Behavioral synchronization, therefore, acts as a social glue in dogs too. It is the first time that such a human-like ability has been highlighted in domesticated canids at an interspecific level. Implications for the evolution of behavioral synchronization are discussed.

How Live Music Moves Us: Head Movement Differences in Audiences to Live Versus Recorded Music

A live music concert is a pleasurable social event that is among the most visceral and memorable forms of musical engagement. But what inspires listeners to attend concerts, sometimes at great expense, when they could listen to recordings at home? An iconic aspect of popular concerts is engaging with other audience members through moving to the music. Head movements, in particular, reflect emotion and have social consequences when experienced with others. Previous studies have explored the affiliative social engagement experienced among people moving together to music. But live concerts have other features that might also be important, such as that during a live performance the music unfolds in a unique and not predetermined way, potentially increasing anticipation and feelings of involvement for the audience. Being in the same space as the musicians might also be exciting. Here we controlled for simply being in an audience to examine whether factors inherent to live performance contribute to the concert experience. We used motion capture to compare head movement responses at a live album release concert featuring Canadian rock star Ian Fletcher Thornley, and at a concert without the performers where the same songs were played from the recorded album. We also examined effects of a prior connection with the performers by comparing fans and neutral-listeners, while controlling for familiarity with the songs, as the album had not yet been released. Head movements were faster during the live concert than the album-playback concert. Self-reported fans moved faster and exhibited greater levels of rhythmic entrainment than neutral-listeners. These results indicate that live music engages listeners to a greater extent than pre-recorded music and that a pre-existing admiration for the performers also leads to higher engagement.

How Moving Together Binds Us Together: The Social Consequences of Interpersonal Entrainment and Group Processes

Interpersonal entrainment has been shown to have a wide variety of social consequences which span far beyond those that could be considered purely pro-social. This work reviews all of the social effects of entrainment and the various explanations for them. The group formation framework emerges as a parsimonious account claiming that as we entrain our sense of self is temporarily diluted as an interdependent identity becomes more salient, thus leading to a range of social and psychological consequences which are pro-group. The sense of belonging arising from moving together is conducive towards pro-social behaviours; yet, it also makes the individual more susceptible to adopting the ideology of the group without critical thinking. We argue that the wide landscape of interpersonal entrainment’s effects reflects its primary effect, de-individuation, and the formation of a common group identity amongst co-actors.

Effects of coordination and gender on prosocial behavior in 4-year-old Chinese children

In a block-assembly task with 138, 4-year-old Chinese kindergarten children, tested in pairs, we manipulated whether fine-grained coordination was required for accomplishing a shared goal with the same end product: building two adjoined towers with alternating levels of orange and green colored blocks to match a depicted model. In the coordination condition, each child had blocks of only one color and built the towers together. In the shared-goal-only condition, each child had both color blocks and built one of the towers, which they then adjoined. We predicted that children in the coordination condition would be more prosocial than children in the shared-goal-only condition. Studies with Western children typically find that girls are more generous than boys. However, we predicted the opposite pattern because Chinese culture emphasizes the importance of generosity more for males than females. Children in the coordination condition were more willing to help their partner complete an unrelated task and were more generous in sharing stickers with unknown children in a dictator game. These results demonstrate that level of coordination affects prosociality above and beyond having a shared goal, and are the first demonstration that prosocial effects of a collaborative task with children generalize beyond the participants to anonymous strangers. Boys shared more stickers with unknown children than girls, suggesting that gender differences in generosity are, in part, culturally conditioned.

Dynamics of Simultaneous and Imitative Bodily Coordination in Trust and Distrust

Body synchronization between interacting people involves coordinative movements in time, space and form. The introduction of newer technologies for automated video analysis and motion tracking has considerably improved the accurate measurement of coordination, particularly in temporal and spatial terms. However, the form of interpersonal coordination has been less explored. In the present study we address this gap by exploring the effect of trust on temporal and morphological patterns of interpersonal coordination. We adapted an optical motion-capture system to record spontaneous body movements in pairs of individuals engaged in natural conversations. We conducted two experiments in which we manipulated trust through a breach of expectancy (Study 1: 10 trustful and 10 distrustful participants) and friendship (Study 2: 20 dyads of friends and 20 dyads of strangers). In Study 1, results show the participants' strong, early mirror-like coordination in response to the confederates' breach of trust. In Study 2, imitative coordination tended to be more pronounced in pairs of friends than in pairs of non-friends. Overall, our results show not only that listeners move in reaction to speakers, but also that speakers react to listeners with a chain of dynamic coordination patterns affected by the immediate disposition of, and long-term relationship with, their interlocutors.

Timing Deficits in ADHD: Insights From the Neuroscience of Musical Rhythm

Everyday human behavior relies upon extraordinary feats of coordination within the brain. In this perspective paper, we argue that the rich temporal structure of music provides an informative context in which to investigate how the brain coordinates its complex activities in time, and how that coordination can be disrupted. We bring insights from the neuroscience of musical rhythm to considerations of timing deficits in Attention Deficit/Hyperactivity Disorder (ADHD), highlighting the significant overlap between neural systems involved in processing musical rhythm and those implicated in ADHD. We suggest that timing deficits warrant closer investigation since they could lead to the identification of potentially informative phenotypes, tied to neurobiological and genetic factors. Our novel interdisciplinary approach builds upon recent trends in both fields of research: in the neuroscience of rhythm, an increasingly nuanced understanding of the specific contributions of neural systems to rhythm processing, and in ADHD, an increasing focus on differentiating phenotypes and identifying distinct etiological pathways associated with the disorder. Finally, we consider the impact of musical experience on rhythm processing and the potential value of musical rhythm in therapeutic interventions.

Precursors to the performing arts in infancy and early childhood

Across cultures, aspects of music and dance contribute to everyday life in a variety of ways that do not depend on artistry, aesthetics, or expertise. In this chapter, we focus on precursors to music and dance that are evident in infancy: the underlying perceptual abilities, parent-infant musical interactions that are motivated by nonmusical goals, the consequences of such interactions for mood regulation and social regulation, and the emergence of rudimentary singing and rhythmic movement to music. These precursors to music and dance lay the groundwork for our informal engagement with music throughout life and its continuing effects on mood regulation, affiliation, and well-being.

Rhythm and melody as social signals for infants

Infants typically experience music through social interactions with others. One such experience involves caregivers singing to infants while holding and bouncing them rhythmically. These highly social interactions shape infant music perception and may also influence social cognition and behavior. Moving in time with others-interpersonal synchrony-can direct infants' social preferences and prosocial behavior. Infants also show social preferences and selective prosociality toward singers of familiar, socially learned melodies. Here, we discuss recent studies of the influence of musical engagement on infant social cognition and behavior, highlighting the importance of rhythmic movement and socially relevant melodies.

The Psychology of Rituals: An Integrative Review and Process-Based Framework

Traditionally, ritual has been studied from broad sociocultural perspectives, with little consideration of the psychological processes at play. Recently, however, psychologists have begun turning their attention to the study of ritual, uncovering the causal mechanisms driving this universal aspect of human behavior. With growing interest in the psychology of ritual, this article provides an organizing framework to understand recent empirical work from social psychology, cognitive science, anthropology, behavioral economics, and neuroscience. Our framework focuses on three primary regulatory functions of rituals: regulation of (a) emotions, (b) performance goal states, and (c) social connection. We examine the possible mechanisms underlying each function by considering the bottom-up processes that emerge from the physical features of rituals and top-down processes that emerge from the psychological meaning of rituals. Our framework, by appreciating the value of psychological theory, generates novel predictions and enriches our understanding of ritual and human behavior more broadly.

Imagined Steps: Mental Simulation of Coordinated Rhythmic Movements Effects on Pro-sociality

Rhythmically coordinating with a partner can increase pro-sociality, but pro-sociality does not appear to change in proportion to coordination success, or particular classes of coordination. Pro-social benefits may have more to do with simply coordinating in a social context than the details of the actual coordination (Cross et al., 2016). This begs the question, how stripped down can a coordination task be and still affect pro-sociality? Would it be sufficient simply to imagine coordinating with others? Imagining a social interaction can lead to many of the same effects as actual interaction (Crisp and Turner, 2009). We report the first experiments to explore whether imagined coordination affects pro-sociality similarly to actual coordination. Across two experiments and over 450 participants, mentally simulated coordination is shown to promote some, but not all, of the pro-social consequences of actual coordination. Imagined coordination significantly increased group cohesion and de-individuation, but did not consistently affect cooperation.

Interpersonal Coordination: Methods, Achievements, and Challenges

Research regarding interpersonal coordination can be traced back to the early 1960s when video recording began to be utilized in communication studies. Since then, technological advances have extended the range of techniques that can be used to accurately study interactional phenomena. Although such a diversity of methods contributes to the improvement of knowledge concerning interpersonal coordination, it has become increasingly difficult to maintain a comprehensive view of the field. In the present article, we review the main capture methods by describing their major findings, levels of description and limitations. We group them into three categories: video analysis, motion tracking, and psychophysiological and neurophysiological techniques. Revised evidence suggests that interpersonal coordination encompasses a family of morphological and temporal synchronies at different levels and that it is closely related to the construction and maintenance of a common social and affective space. We conclude by arguing that future research should address methodological challenges to advance the understanding of coordination phenomena.

Gender and autistic traits modulate implicit motor synchrony

Interpersonal motor synchrony during walking or dancing is universally observed across cultures, and this joint movement was modulated by physical and social parameters. However, human interactions are greatly shaped by our unique traits, and self-related factors are surprisingly little studied in the context of interpersonal motor synchrony. In this study, we investigated two such factors known to be highly associated with motor coordination: gender and autistic traits. We employed a real-world task extending our understanding beyond laboratory tasks. Participants of the same gender were paired up to walk and chat in a natural environment. A cover story was introduced so that participants would not know their walking steps were being recorded and instead believed that their location was being tracked by a global positioning system (GPS), so they would ignore the motor recording. We found that the female pairs’ steps were more synchronized than those of the males, and higher autistic tendencies (measured by the autism-spectrum quotient) attenuated synchronous steps. Those who synchronized better had higher impression rating increase for their walking partners (measured by interpersonal judgement scale) than those who synchronized less well. Our results indicated that the participants’ joint movements were shaped by predisposed traits and might share similar mechanism with social functions such as empathy.

How interpersonal synchrony facilitates early prosocial behavior

When infants and children affiliate with others, certain cues may direct their social efforts to 'better' social partners. Interpersonal synchrony, or when two or more people move together in time, can be one such cue. In adults, experiencing interpersonal synchrony encourages affiliative behaviors. Recent studies have found that these effects also influence early prosociality-for example, 14-month-olds help a synchronous partner more than an asynchronous partner. These effects on helping are specifically directed to the synchronous movement partner and members of that person's social group. In older children, the prosocial effects of interpersonal synchrony may even cross group divides. How synchrony and other cues for group membership influence early prosociality is a promising avenue for future research.

Body sway reflects leadership in joint music performance

The cultural and technological achievements of the human species depend on complex social interactions. Nonverbal interpersonal coordination, or joint action, is a crucial element of social interaction, but the dynamics of nonverbal information flow among people are not well understood. We used joint music making in string quartets, a complex, naturalistic nonverbal behavior, as a model system. Using motion capture, we recorded body sway simultaneously in four musicians, which reflected real-time interpersonal information sharing. We used Granger causality to analyze predictive relationships among the motion time series of the players to determine the magnitude and direction of information flow among the players. We experimentally manipulated which musician was the leader (followers were not informed who was leading) and whether they could see each other, to investigate how these variables affect information flow. We found that assigned leaders exerted significantly greater influence on others and were less influenced by others compared with followers. This effect was present, whether or not they could see each other, but was enhanced with visual information, indicating that visual as well as auditory information is used in musical coordination. Importantly, performers' ratings of the "goodness" of their performances were positively correlated with the overall degree of body sway coupling, indicating that communication through body sway reflects perceived performance success. These results confirm that information sharing in a nonverbal joint action task occurs through both auditory and visual cues and that the dynamics of information flow are affected by changing group relationships.