Behavioral Synchrony and its Prosocial Consequences: Is Simply Sharing a Beat Sufficient?

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Behavioral Synchrony and its Prosocial Consequences:

Is Simply Sharing a Beat Sufficient?

Research Report

MSc in Brain and Cognitive Sciences, Track Cognitive Science,

University of Amsterdam

Student: Jeannette van Ditzhuijzen (11116587) Number of ECTS: 36 ECTS

Time period: 30/01/2017 - 18/08/2017 Supervisor: Dr. Makiko Sadakata

Co-assessor: Dr. Ashley Burgoyne

UvA Representative: Dr. Ashley Burgoyne Research Institute: Institute for Logic, Language and Computation, Universiteit van Amsterdam Research group: Music Cognition Group

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Behavioral Synchrony and its Prosocial Consequences:

Is Simply Sharing a Beat Sufficient?

ABSTRACT

Prior research suggests that behavioral synchronization is key in establishing prosocial effects. However, in the current study, it is hypothesized that movement symmetry is not a crucial factor in achieving these prosocial outcomes, but it is more a matter of coordinating movements to a shared temporal regularity. The effect of movement coordination on cognitive empathy, pain threshold and prosocial commitment was examined by comparing three movement conditions; synchronous drumming, interactional synchronous drumming (different movements are performed to the same beat), and non-synchronous drumming. The obtained results indicated that prosocial commitment significantly increased after either drumming synchronous or interactional synchronous, in comparison to non-synchronous drumming. This indicates that merely moving to the same beat is sufficient in establishing cooperative behavior, conform to our prediction. No significant differences were found concerning pain threshold and cognitive empathy, although findings regarding cognitive empathy pointed in similar directions where cognitive empathy seems to be enhanced after both synchronous and interactional synchronous drumming, relative to non-synchronous drumming. The current research contributes to the growing literature on the prosocial consequences of behavioral synchrony by suggesting that movement symmetry may not be essential in establishing cooperative behavior, rather, it seems important to entrain movements to a shared beat representation.

Introduction

Several studies have suggested that behavioral

synchrony, where two or more people perform

similar movements in time (Miles, Griffiths, Richardson, & Macrae, 2010), has a variety of prosocial consequences (e.g. Demos, Chaffin, Begosh, Daniels, & Marsh, 2012; Tarr, Launay, & Dunbar, 2015; Wiltermuth & Heath, 2009). For instance, research indicated that synchronized group dancing or chair-rocking may lead to increased feelings of social closeness between participants (Demos et al., 2012; Tarr, Launay, & Dunbar, 2015). Additionally, Wiltermuth & Heath (2009) presented evidence that groups who engaged in a synchronized walking activity showed enhanced cooperative behavior in subsequent economic games, in comparison to those who had walked non-synchronously. While the prosocial consequences of behavioral synchrony have been studied extensively, there is yet no consensus on the underlying mechanism by which this might occur (Tarr, Launay, & Dunbar, 2014). Currently, the most promising theory proposes that the process of self-other merging, via so-called mirror neurons, might be of importance in

synchronized behavior (Gallese, Keysers, & Rizzolatti, 2004; Hove & Risen, 2009; Tarr et al., 2014). According to this theory, similar neuronal circuits are recruited in both the actor and perceiver, increasing the likelihood and ease with which a matched action can be performed (Brass, Bekkering, & Prinz, 2001). Consequently, these shared representations of action-perception coupling may extend to a shared representation of self and other (Hove & Risen, 2009; Hurley, 2008), which subsequently may play a role in strengthening feelings of affiliation and social cooperation between participants (Dijksterhuis & Bargh, 2001; Hurley, 2008).

Behavioral synchrony is present during music practices as well (Launay, Tarr, & Dunbar, 2016), for instance during group drumming or singing (Cohen, Mundry, & Kirschner, 2014; Good & Russo, 2016), which might explain why music is often considered as a tool to foster social cohesion (Cross & Morley, 2009; Gielen, Elkhuizen, van den Hoogen, Lijster, & Otte, 2014; Launay, Tarr, & Dunbar, 2016; Trehub, Becker, & Morley, 2015). Throughout history, music is suggested to play an important, and possibly adaptive role in the management of

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social relationships (Trehub et al., 2015; Laurence, 2015; Brown, 2000). Particularly within larger groups musical practices may be beneficial for social bonding, since music is not limited to one-on-one interactions but can reach across multiple individuals at the same time (Weinstein, Launay, Pearce, Dunbar, & Stewart, 2016).

However, during music performances, strict behavioral synchrony is not necessarily present at all times. Groups regularly produce music effectively without moving their body parts identically, such as in musical ensembles or orchestras (Kokal, Engel, Kirschner, & Keysers, 2011). During music making, it is more a matter of coordinating actions in reference to a shared beat, rather than strict behavioral synchrony (Hayward, 2014). The aim of the current study is to examine the suggested prosocial consequences of behavioral synchrony in more detail. Specifically, we aimed to investigate whether movement symmetry is essential in establishing prosocial effects, or whether it is more important to coordinate the tempo of our actions at a higher and more abstract level, i.e., the beat. If similar prosocial outcomes, such as enhanced cooperative behavior, follow from merely moving to the same beat, this would imply that movement symmetry is not essential in affecting social behavior, instead,

psychological synchronization (simply moving

to a shared beat representation) would be key in enhancing prosocial behaviors.

The idea that psychological synchrony through music is already sufficient in establishing prosocial behavior is supported by the SAME (Shared Affective Motion Experience) model of emotional responses to music (Overy & Molnar-Scakacs, 2009). The SAME model suggests that music is perceived as a series of intentional, hierarchically organized sequences of expressive motor actions, recruiting similar neural networks in performers and perceivers (Overy & Molnar-Scakacs, 2009). According to this model, synchronization of neuronal networks between multiple performers and listeners,

may lead to “a sense of empathy and social bonding” (Overy, 2012, p. 66). Additionally and affirmatively, various dual-electroencephalography (EEG) studies, where EEG signals are recorded of two participants simultaneously, revealed brain oscillatory couplings between subjects performing and improvising on the guitar (Lindenberger, Li, Gruber, & Müller, 2009; Müller, Sänger, & Lindenberger, 2013; Sänger, Müller, & Lindenberger, 2012). These findings confirm synchronization of neuronal cell assemblies through musical activity, even when performative actions differ between interacting partners (Müller et al., 2013). Currently there is only little evidence to support our hypothesis: prior studies on behavioral synchrony and prosocial consequences almost exclusively examined movement synchrony, whilst comparing it with non-synchronous movement (e.g. Tarr et al., 2015; Wiltermuth & Heath, 2009). To our knowledge, only a small amount of studies has investigated the social effects of movement coordination in reference to a shared beat (Cirelli, Einarson, & Trainor, 2014; Cross, Wilson, & Golonka, 2016; Lakens, 2010; Sullivan, Rickers, & Gammage, 2014; Tarr, Launay, & Dunbar, 2015) showing rather mixed evidence.

On the one hand, research suggests that psychological synchrony leads to similar levels of cooperation and perceived entitativity (perceiving a group as a team; Reddish et al., 2016) as behavioral synchrony (Cross et al., 2016; Lakens, 2010), even in 14-month-old infants (Cirelli et al., 2014). However, on the other hand research indicates that significant increases of social closeness are only presented after performing synchronized dance movements. Subjects who perform dissimilar dance movements to a shared beat seem to experience considerably lower feelings of social closeness towards each other (Tarr, Launay, & Dunbar, 2015). Moreover, research investigating the effect of behavioral synchrony on pain threshold shows contrasting findings as well, where solely movement symmetry seems to lead to an

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elevation of pain threshold (Sullivan et al., 2014; Tarr, Launay, & Dunbar, 2015). Pain threshold is of interest because it is related to the Endogenous Opioid System (EOS), and particularly endorphin (Cohen, Ejsmond-Frey, Knight, & Dunbar, 2010; Goldstein & Grevert, 1978; Tarr, Launay, & Dunbar, 2015). Elevated endorphin levels seem to be in turn connected to social bonding behaviors (Curley & Keverne, 2005; Martel et al., 1995; Machin & Dunbar, 2011). Taken together, these contrasting results regarding the social effects of psychological synchrony indicate that more research is necessary.

Even though the aforementioned results suggest that only strict movement symmetry may influence endorphin release (Sullivan et al., 2014; Tarr, Launay, & Dunbar, 2015), Launay, Tarr, & Dunbar (2016) claim that activities including musical interaction, without movement synchrony, are associated with EOS activity as well. Additionally, research suggests that musical activities such as drumming and group singing may elevate pain threshold (Dunbar, Kaskatis, MacDonald, & Barra, 2012; Weinstein et al., 2016). In order to arrive at more robust conclusions regarding the relationship between synchrony, musical activity and the EOS, the current study is taking pain threshold into consideration as one of the dependent measurements.

Besides EOS activity, two other dependent measurements of prosocial behavior are taken into account in the current research, namely cognitive empathy and participants’ prosocial commitment towards co-performers. Cognitive empathy is the ability to recognize and understand another person’s perspective (Shamay-Tsoory, Aharon-Peretz, & Perry, 2009), and we believe it has never been specifically part of synchronization research before, since synchronization effects are mainly reported on self-reported feelings of social rapport and cooperative behavior (e.g. Miles, Nind, & Macrae, 2009; Tarr, Launay, & Dunbar, 2015; Wiltermuth & Heath, 2009). According to Rabinowitch (2015) music participation may promote empathy via the concept of merged subjectivity, where

normally rigid boundaries between subjects may blur through a certain sensorimotor mismatch (Rabinowitch, Cross & Burnard, 2012). In other words, in musical group performances, certain sounds produced by others can be experienced as originating from oneself, or one might perceive a sound produced by oneself as originating from a co-performer. This particular experience of merging sound sources, may consequently merge self-other boundaries (Rabinowitch, Cross & Burnard, 2012). Although self-other merging has been mentioned earlier in this introduction (Gallese et al., 2004; Tarr et al., 2014), this latter account on self-other merging does not seem to imply a high relevance for the activation of mirror neurons. Rather, perception of the produced sound signals seem to play a significant role.

The dependent measurement of prosocial commitment has, to the best of our knowledge, been part of investigation one time before in synchrony research (Kokal et al., 2011). Here, the effect of synchronized drumming on helping behavior was examined, using a pencil-dropping task (see Kokal et al., 2011). The observed findings indicated that those who drummed in synch with the experimenter, were more likely to help the experimenter pick up the ‘accidentally’ dropped pencils, relative to those drumming non-synchronous with the experimenter (Kokal et al., 2011). And interestingly, the observed prosocial commitment effect was even stronger in participants that acquired the rhythm more easily (Kokal et al., 2011). The current research therefore extends the study of Kokal et al. (2011) by taking the factor of musical background into account. Moreover, another type of synchronous drumming was implemented in the current study, namely

interactional synchrony, where individuals

move to the same temporal regularity, but not necessarily perform identical movements (Lakens, 2010). In addition, in order to prevent experimenter effects influencing the results (Rennung & Göritz, 2016), the pencil task used by Kokal et al. (2011) was adjusted to measure prosocial commitment between participants,

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thus, excluding the experimenter. Lastly, the current study assessed participants’ subjective mood-arousal levels, to assure that possible social effects of synchronization activities cannot be attributed to differences in enjoyment or pleasure (Dunbar et al., 2012; Kniffin, Yan, Wansink, & Schulze, 2016). In summary, based on previous results claiming prosocial consequences after behavioural synchrony, the aim of the current research is to study this in more depth and investigate whether the observed social effects of behavioral synchrony may actually in part be explained by mere psychological synchronization. It is hypothesized that movement symmetry is not a crucial factor in achieving prosocial outcomes, as long as participants coordinate their movements to the same beat. In order to investigate whether current evidence on prosocial consequences of coordination are in fact restricted to instances where the performers physically synchronize, different drumming conditions will be compared in this study. Specifically, subject pairs either perform identical movements to a shared beat (synchrony), execute different movements to a shared beat (interactional synchrony), or perform dissimilar actions to a differing beat (non-synchrony). Prosocial behavior is being examined via cooperative behavior towards each other and pain threshold, as these measures have been actively investigated in prior studies (e.g. Kokal et al., 2011; Tarr, Launay, & Dunbar, 2015; Wiltermuth & Heath, 2009). In addition, cognitive empathy is taken into consideration as it is an important factor in prosocial and cooperative behavior (Eisenberg & Miller, 1987). Particularly drumming is implemented as a synchronous activity since it is one of the most universal forms of musical activity (Cohen, 2015). In addition, drumming provides clear auditory cues of synchronous action, in comparison to performing collective dance movements, for example (Tarr, Launay, & Dunbar, 2015). Consequently, the clear auditory feedback provided by the drums, might decrease the degree of difficulty for participants without musical experience. If

active music participation can create a situation that potentially enhances social behavior, it might be of significant value in educational and therapeutic contexts, especially for those suffering from social deficits, such as with autism spectrum disorder (Ghasemtabar et al., 2015).

Methods

Participants

Thirty-six adult participants (22 females, x̅ age = 25.14, SD = 3.32 years) were recruited and matched into unacquainted dyads. Subjects who were diabetic, pregnant, or who drank alcohol or smoked within two hours prior to the experiment did not take part in the study (following Dunbar et al., 2012). One participant was excluded from analysis since she had reached ceiling level for pain threshold measurements. Ethical consent was provided by the Ethics Committee of the Universiteit van Amsterdam (dossier 2017-15).

Task & Measurements

Drumming Task

The task of the subjects was to drum a rhythm that was presented in an instruction video, as correctly as possible, for 3-5 minutes. During the drumming task, participants were randomly assigned to one of the following conditions differing in beat and movement symmetry between participant pairs:

• Synchronous drumming: Subjects were instructed to drum the rhythm presented in Figure 1A. Thus, subjects performed similar movements in reference to the same metronome beat (70 bpm).

• Interactional synchronous drumming: In this condition, the rhythm of the synchronous condition was divided over two subjects (see Figure 1B & C). Ultimately, participants would perform different arm gestures by taking turns in hitting the drum. Playing rhythms B and C simultaneously results in rhythm A.

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• Non-synchronous drumming: In this control condition, subjects both drummed the rhythm represented in Figure 1A. However, in order to break down the coordination between partners and enhance non-synchronization, subjects drummed the rhythm in different phase-shifts and slightly different tempi (65 bpm and 70 bpm).

During the drumming task, all pairs had 2-3 minutes to practice the task. During the practice phase, metronome beats and the target rhythm was repeatedly played over headphones and the participants practiced along with the rhythm. Afterwards, subjects drummed the target rhythm to metronome beats that were presented through speakers. Completing 10 successful trials was used as a cut-off point to end the performance phase during the synchrony and interactional synchrony conditions. It took typically 3-5 minutes. Participants in the non-synchronous condition had a similar practice phase. For the performance phase, subjects listened to individual metronomes over headphones and drummed the target rhythm in reference to the individual metronome beats for 3 minutes. For all participant-pairs, a visual representation of the rhythms was present to assist the participants in the drumming task.

Measurements

Social Rapport

Social rapport between participants was assessed via questions similar to those used by

Hove & Risen (2009), Valdesolo, Ouyang, & DeSteno (2010) and Wiltermuth & Heath (2009) concerning connectedness, similarity, trust, likeability and closeness. To give an example, the following questions were included: ‘How connected do you feel with the other participant?’ and ‘How similar do you feel to the other participant?’ Answers were given on a 7-point Likert scale. Further, self/other overlap was measured with The Inclusion of Other in the Self scale (IOS) (Aron, Aron, & Smollan, 1992). The social rapport questionnaire, as well as other measurements, are included in the Supplementary Materials (SM).

Mood Questionnaire

Subjective measurements of participants’ mood and arousal levels were taken into consideration using sliders together with the Self-Assessment Manikin (SAM; Bradley & Lang, 1994), to produce a continuous scale with ratings from 0-100. In addition, translated Japanese mood assessments were included where twelve items in three dimensions (negative, arousal and calm) were rated with a 5-point Likert scale (see SM) (Arai, Takenaka & Oka, 2003).

Dispositional Empathy & Musical Background

Participants completed the Interpersonal Reactivity Index (IRI) (Davis, 1983), serving as an index of their dispositional empathy. The IRI is a self-report questionnaire consisting of 28 items, designed to measure both emotional and cognitive empathy. The IRI consists of the

Figure 1 – Rhythms used in the study, shown in musical notation. Notes situated in the upper part of the staff are played

with the left hand and notes in the lower part with the right hand. Figure 1A is the rhythm presented in the synchronous and asynchronous conditions. Figures 1B and 1C represent the rhythms of participant 1 and participant 2 respectively, of the interactional synchrony condition.

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following four subscales of seven items: perspective taking (IRI-PT), fantasy (IRI-FS), empathic concern (IRI-EC), and personal distress (IRI-PD).

Musical experience was measured using the Goldsmith Musical Sophistication Index, including the Beat Perception listening test (Müllensiefen, Gingras, Musil, & Stewart, 2014; Iversen & Patel, 2008).

Synchronization Accuracy

Acoustic signals were measured via MIDI recordings. However, this data was not included in the current report due to time constraints.

Dependent Variables

Cognitive Empathy

The Reading the Mind in the Eyes Task (from now on referred to as the Eyes task) was used to assess cognitive empathy (Baron-Cohen et al., 2015; Baron-Cohen, Wheelwright, Hill, Raste, & Plumb, 2001). In this task participants were exposed to thirty-six randomly ordered gray-scale photos of human eyes, presented together with four mental state terms, such as ‘amused’, ‘disappointed’, ‘relaxed’ and ‘depressed’. For every photo, subjects were instructed to choose the word best describing the state of the person on the photo. Only one of the four items was correct. Four pictures of two leading experimenters were implemented into the task as well, including one with a negative valence and one with a positive valence of both researchers. This resulted in a total of 40 pictures.

Since the Eyes task was registered twice in a relatively short period of time, both before and after the drumming task, the task was split into two versions. The division of pictures was based on a small pilot study (n = 15), in which subjects completed the Eyes task. Subsequently, the Eyes task was spilt into two versions, both consisting of ten easy questions (score of correct responses > 10) and ten difficult questions (score of correct responses <= 10), resulting in 20 pictures for both the pre- and post-measurement (Domes,

Heinrichs, Michel, Berger, & Herpertz, 2007) (see SM for the division of questions).

Pain Threshold

A blood pressure cuff was used to induce ischemic pain, as it has been found to be a valid and commonly used procedure for pain threshold in studies on behavioral synchrony (Cohen et al., 2014; Dunbar et al., 2012; Sullivan et al., 2014). Ischemic pain was induced through manual pumping of the cuff. Pressure was increased at a steady rate (10 mmHG/sec) and participants expressed the point at which the pressure became uncomfortable by saying ‘now’. Subsequently, the cuff was removed and the pressure recorded in mmHG. The two leading experimenters whom administered pain thresholds, were switched over participants between the pre- and post-measurements, to blind them for subjects’ pre-pain threshold value.

Prosocial Commitment Test

This test was performed to measure subjects’ prosocial commitment towards their partner-participant. At the end of the experimental session, participant-pairs were specifically instructed to collect materials from a table situated in the experimental room, whilst the experimenters left the room. One of the participants was instructed to take along a stack of papers and the other a cup filled with twelve pencils. However, the cup was manipulated so that the moment one of the participants picked it up, all twelve pencils fell on the floor. Right after the participants collected all pencils, the experimenters entered the room again and counted the number of pencils picked up by the other participant. The amount of pencils collected by this ‘helping participant’, served as a measure of prosocial commitment for one of the two participants in a pair (the task is adjusted from Kokal, Engel, Kirschner, & Keysers, 2011).

Procedure

Prior to the experimental session, participants completed a Qualtrics survey at home,

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including a demographic questionnaire and the Goldsmith Musical Sophistication Index. When arriving at the experiment venue, couples received instructions together with the informed consent form. Afterwards, subjects completed an online Qualtrics survey including the IRI, social rapport and mood-arousal questions, and the pre-Eyes task. Following, pain threshold was assessed in individual rooms serving as pre-manipulation value. Subsequently, subjects received individual video instructions concerning the rhythm they had to drum according to the assigned condition, followed by the drumming practice task and the performance task. At the beginning of the drumming task, subjects were instructed not to speak with one another. Immediately after completion of the drumming task, pain threshold was assessed in individual locations again, followed by the following posttest measures: post-Eyes task, social rapport questions, mood-arousal ratings, and questions regarding perceived success, difficulty and enjoyment of the drumming session. Right before exiting the experimental room, the prosocial commitment test was administered. The entire session lasted approximately one hour. Among the participants, ten prizes were distributed via a lottery, including free drumming lessons and Bol.com vouchers.

Apparatus

The experimental set-up of the room is presented schematically in Figure 2. Online questionnaires and video instructions were presented on individual laptops. The drumming task was performed on two digital percussion pads (Octapad Roland SPD-30 and Total Percussion Pad Roland SPD-20). In front of the percussion pads, a full-length mirror (65 x 150 cm) was placed horizontally, so that subjects could each view both of their upper bodies and the movements they made (following Cross et al., 2016). The visual representations of the rhythms were placed above the mirror. The defected plastic cup filled with twelve pencils was placed in an open closet in the room, next to a pack of paper.

Data Analysis

First, five mixed analyses of variance (ANOVA) were performed to check the effect of drumming condition (independent variable) on mood-arousal levels (dependent variables), consisting of the two dimensions of the Self-Assessment Manikin (arousal and valence) and the three dimensions of the Japanese mood assessment (negative, arousal and calm). The change in social rapport before and after the drumming session was also examined over conditions with non-parametric Kruskal-Wallis tests, since the social rapport variables were non-normally distributed. In addition, perceived difficulty, enjoyment and success of the different groups were explored with these analyses.

Second, dispositional empathy and cognitive empathy scores were processed and coded in MATLAB (R2016a, The MathWorks Inc.). Next, two mixed analysis of covariance (ANCOVA) were performed with the dependent variables of interest (cognitive empathy and pain threshold). Time point (pre & post) was used in these analyses as within-subjects factor and drumming condition was implemented as the between-subjects factor. In addition, musical experience was added as control variable, as well as the IRI subscale perspective taking in case of the cognitive empathy analysis. Following, a one-way ANCOVA was executed with the prosocial commitment task as dependent variable and drumming condition as between-subjects factor. Additionally, the IRI subscale empathic concern and musical background were added

Figure 2 – Simplified and schematic representation of the

experimental room. The digital percussion pads, laptops, chairs, mirror, pack of paper and cup of pencils are situated in the room.

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as covariates to this analysis. Since only half of the subject sample executed the latter task, and in some experimental sessions the task was not executed properly, the sample size for this analysis was smaller (n = 12).

Local effect sizes of drumming condition were calculated using Cohen’s d as described in Cohen (1988). The data was checked and generally met assumptions regarding normality and homogeneity of variances (see SM). If the assumption of normality was violated, the non-parametric alternative was performed. Specifically, the Kruskal-Wallis test was used with drumming condition as independent variable.

Results

Baseline differences

There was a significant overall increase over time in the Japanese mood dimension of arousal (F(1) = 15.00, p < .01), as well as an

enhancement of valence measured by the Self-Assessment Manikin (F(1) = 6.21, p = .02).

However, these changes did not differ significantly between the different drumming conditions (SM, Table S3 & S4). Thus, even though all participants experienced an enhancement of their arousal and mood levels after the drumming task, no significant differences in this increase of mood-arousal levels were observed between the three drumming conditions. In addition, Kruskal-Wallis tests revealed no significant differences in all social rapport questions between the different drumming conditions (see SM, Table S5). At last, no significant differences between conditions in participants’ ratings of perceived success, difficulty or enjoyment were observed (SM, Table S6). Therefore, there were no

baseline differences between drumming conditions regarding mood, social rapport, task enjoyment, perceived task difficulty or perceived success, and thus, it was concluded that that these factors did not contribute to the effects described below.

Cognitive Empathy

The average scores of the pre- and post-Eyes task for the different conditions are presented in Table 1. A mixed ANCOVA showed that the mean of the Eyes task did not differ significantly between time points (F(1, 30)= .19,

p = .67). Additionally, even though both synchronous and interactional drumming resulted in a greater increase of cognitive empathy scores (Msynch = 2.23, SDsynch = 2.05,

Minteractional = 2.25, SDinteractional = 2.49) than

asynchronous drumming (Masynch = .30, SDasynch

= 3.62) (see Table 1), a mixed ANCOVA revealed no significant interaction between time point and drumming condition (F(2, 30) =

2.44, p = .10). This indicates that there was no significant difference in cognitive empathy between the drumming conditions when statistically controlling for the variables of musical background and perspective taking. Nonetheless, the calculated effect size of the interaction between time point and drumming condition was relatively large (d = .81), indicating an influence of drumming condition on cognitive empathy scores. Perhaps, the current study might have had too little power to result in a significant effect. As can be seen in Table 1, the different drumming conditions show differences in their pre-Eyes score, thus an additional ANCOVA was performed. However, no significant differences between the pre-Eyes score was found between conditions when controlling for the perspective taking subscale (F(2, 31)= 1.33, p =

.28).

Table 1 – Means and standard deviations of pre and post scores of the Eyes task and pain threshold

measurements (in mmHG) for the different drumming conditions

Reading the Mind in the Eyes Pain Threshold Drumming

condition

Pre score Post score Pre score Post score

M SD M SD M SD M SD

Synchrony 12.69 2.81 14.92 1.71 141.54 56.23 138.08 52.34

Interactional

synchrony 13.08 1.98 15.33 1.50 154.83 55.80 170.50 73.60

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Table 1 presents the average pre- and post-pain threshold scores. As can be seen, subjects in the synchronous drumming condition experienced, on average, a slight decrease in pain threshold (Msynch = -3.46, SDsynch = 33.51),

whereas both interactional drumming and asynchronous drumming resulted in an increase in pain threshold (Minteractional = 15.67,

SDinteractional = 50.87, Masynch = 5.40, SDasynch =

46.01). A mixed ANCOVA indicated no significant difference of pain threshold between time points (F(1, 31) = .11, p = .75).

Additionally, no significant interaction was found for time point and drumming condition when statistically controlling for musical experience (F(2, 31)= .71, p = .50), with a medium

effect size (d = .43). These results indicate that the increase or decrease in pain threshold did not differ significantly after drumming in synchrony, interactional synchrony or asynchronous.

Prosocial Commitment

In Figure 3 the results of the prosocial commitment task are presented, displaying the mean number of pencils picked up per condition. On average, subjects collected more pencils of their partner when they either

Figure 3 – Prosocial commitment test results of the

different drumming conditions. Mean of the number of pencils collected is displayed. The error bars represent standard deviations. * indicate significant differences

between the conditions at an alpha level below .05

drummed in synchrony (M = 5.75, SD = .96 pencils) or interactional synchrony (M = 6.50, SD = 1.30 pencils) compared with drumming non-synchronous with their partner (M = 1.25, SD = 1.50 pencils). Accordingly, a one-way ANCOVA showed a significant effect of drumming condition on the pencil task (F(2,7) =

31.64, p < .01) when controlling for IRI-EC and musical background. Additionally, drumming condition was observed to have a large effect size (d = 6.10). Post-hoc comparisons using paired t-tests with Bonferroni correction revealed a significant difference between both asynchronous drumming and synchronous drumming (p < .01), and asynchronous drumming and interactional synchronous drumming (p < .01). Subjects drumming non-synchronous collected remarkably fewer pencils than the other two conditions. Post-hoc comparisons indicated no significant difference between the synchronous and interactional drumming conditions.

Discussion

The present study examined the role of psychological synchrony, that is, coordinating actions to a shared temporal regularity, in the prosocial consequences of behavioral synchrony. More concretely, the social influence of group movement coordination was investigated by examining the social effects of a dyadic drumming task on cognitive empathy, pain threshold and prosocial commitment. In line with our prediction, we observed that both synchronous movement and interactional synchronous movement resulted in enhanced prosocial commitment scores towards the participant’s partner (via a pencil-dropping task) in comparison to subjects moving in asynchrony. No significant influences of movement coordination on both cognitive empathy and pain threshold were observed. Even though previous research showed mixed evidence regarding the social effects of interpersonal synchrony, our finding indicates that movement symmetry may not be crucial in establishing cooperative behavior, but it is rather important to entrain movements to a shared beat representation. The observed effect was not influenced by

0 1 2 3 4 5 6 7 8 9 Synchrony Interactional synchrony Asynchrony N umb er of pe nc ils

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feelings of social rapport between participants, such as connectedness, or mood changes. The results regarding prosocial commitment are consistent with some earlier studies on movement coordination (Cirelli et al., 2014; Cross et al., 2016) and hold in a context more close to a musical setting, where participants are doing more than simple bouncing (Cirelli et al., 2014), waving (Lakens, 2010) or joystick coordination (Cross et al., 2016). Additionally, current findings extend results of the study by Kokal et al. (2011), where subjects drumming in synch picked up relatively more pencils than those drumming non-synchronous. Importantly, our results indicated that not only synchronous drumming, but also interactional synchronous drumming positively affected helping behavior. Therefore, the previous synchronization effect observed by Kokal et al. (2011) may also be explained by the factor that participants simply drummed to a common beat. However, even though our finding regarding prosocial commitment is highly significant, it should be noted that our results are generated from a relatively small sample size (n = 12). In addition, the implemented pencil task is greatly dependent on both participants’ behavior and difficult to control in an experimental design. Thus, we are cautioned to draw firm conclusions from them. Although no statistical significance was found for the cognitive empathy task, current data does point in a direction where a more fluid increase of cognitive empathy is experienced after either synchronous or interactional synchronous drumming, relative to asynchronous drumming. Moreover, since the applied Eyes task mainly incorporated pictures of strangers, this would imply that more generalized prosociality may be increased through collective drumming activities, extending findings of Reddish, Bulbulia, & Fischer (2014). Therefore, by moving to a shared beat, participants may not only show more cooperative behavior towards their co-performer, they may also get better in recognizing and understanding the emotional state of other people with whom they did not interact, thus, experiencing an improvement of their empathic abilities in general. Interestingly, this would indicate that the capacity of cognitive empathy is an ability that can be changed fluidly over time (Laurence,

2015; Stein, 1989) and that it is not a skill people merely can or cannot possess.

Our findings concerning endorphin activity contrasted with previous findings (Sullivan et al., 2014; Tarr, Launay, & Dunbar, 2015). At first sight, the obtained data even suggests exactly opposing directions regarding the influence of synchronicity on pain threshold. Possibly our findings can be explained by the musical elements added to the different synchronous activities, as prior research showing elevated endorphin activity involved simplified movement activities such as rowing (Sullivan, Gagnon, Gammage, & Peters, 2015; Sullivan et al., 2014; Tarr, Launay, & Dunbar, 2015). Moreover, previous findings on EOS activity can possibly be explained by experimenter effects (Rennung & Göritz, 2016), since the same experimenter assessed both pre- and post-pain thresholds in these studies (Sullivan, Gagnon, Gammage, & Peters, 2015; Sullivan et al., 2014; Tarr, Launay, & Dunbar, 2015). We explicitly tried to blind the experimenter from the pre-pain threshold value by switching experimenters over the pre- and post-assessments.

Our social rapport results of connectedness, trust, closeness, similarity, likeability and self/other overlap, were also not in line with previous studies (e.g. Demos et al., 2012; Wiltermuth & Heath, 2009) as no significant differences were observed between the different drumming conditions. This indicates that these interpersonal feelings play no mediating factor in the effect of movement coordination on cooperation (Cross et al., 2016). Our contrasting results can possibly be explained by the fact that most prior research measured the feelings of social rapport solely after the synchronous activity, and subsequently compared the obtained scores between synchronous and non-synchronous activity (e.g. Demos et al., 2012; Tarr, Launay, & Dunbar, 2015; Wiltermuth & Heath, 2009). The current study assessed these relationships both prior to and after drumming activity. Possibly, participants who felt more connected with each other after the (a)synchrony manipulation in previous studies, might have perceived each other as more strongly connected at baseline already. However, as we

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included both pre- and post-measurements, our findings of social rapport may also be caused by a testing effect, where the completion of the pre-drumming questions influenced the answers given in the post-measurement.

Although prior research assumed that behavioral synchronization is key in establishing prosocial effects (e.g. Demos et al., 2012; Tarr, Launay, Cohen, & Dunbar, 2015; Wiltermuth & Heath, 2009), our study indicated that it seems important to just coordinate movements to a common beat. Movement symmetry does not seem to be required. As mentioned earlier, a possible explanation for this observation can be found in the SAME model (Overy & Molnar-Scakacs, 2009), where music is discussed to generate interpersonal neuronal synchronization. Specifically, effects of between-brain synchronization during musical interaction seem to be distinctly found at lower frequencies in fronto-central regions, in the delta and theta frequencies (Lindenberger et al., 2009; Sänger et al., 2012). Interestingly, a study by Szymanski et al. (2017) indicated an association between increases of inter-brain phase synchronization, mainly in the delta frequency band, and subsequent benefits in teamwork, suggesting a facilitative effect of neuronal synchronization on prosocial behavior. Taken together, one can hypothesize that music might have the ability to synchronize brain oscillations of performers into similar lower frequency bands, which in turn may enhance interpersonal social relations on the short term. Future research using neuroimaging is recommended to examine this association in more detail and to help understand the hypothesis regarding between brain synchronization through music. It would be particularly interesting to study this in situations similar to musical ensembles, where subjects perform different movements on different instruments, as this highly resembles musical practices in everyday life. Not only neuronal synchronization may explain the social effects of music participation, processes of adaptation, anticipation and

eventual contingency between one’s own actions and experienced events, might be responsible factors as well (Catmur & Heyes, 2013; Keller, Novembre, & Hove, 2014). Accordingly, prosocial consequences might emerge from the presence of a predictive relationship between one’s movements and those of the other. Both synchronous drumming as well as interactional synchronous drumming involved a form of contingency where participants might have detected that their own actions predicted movements of the other participant, regardless of whether they moved similarly or not. During non-synchronous drumming on the other hand, no predictive relationship between performative actions was present at all. Subsequently, this contingency in performative actions, might have prepared subjects to more easily cognitively engage with mental states of others as well (Baimel, Severson, Baron, & Birch, 2015; Sebanz, Bekkering, & Knoblich, 2006).

An alternative explanation for the obtained prosocial commitment results might also lie within the presence of cooperation during the drumming task itself, as well as shared intentionality (Reddish, Fischer, & Bulbulia, 2013; Wolf, Launay, & Dunbar, 2016). Both synchronous drumming and interactional synchronous drumming demand more cooperative behavior between participants than non-synchronous drumming. Moreover, these former two conditions almost automatically and unconsciously ask participants to perform the task with a collective goal and shared intention. In addition, this differing aspect might have been enhanced by the way the metronome was played during the performance phase. Both the synchronous and interactional synchronous condition listened to the metronome over speakers, whereas participants in the non-synchronous condition perceived it over headphones, diverting their attention to individual sources. It is highly recommended to perform a similar experiment where metronomes are displayed to participants identically in every condition.

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Conclusion

The current study demonstrated that dyads who either drum in synchrony or in interactional synchrony are more cooperative post drumming than people drumming in asynchrony. Findings concerning cognitive empathy pointed in similar directions, thus, replicative research is highly recommended to either confirm or contradict our predictions. Remarkably, the obtained results regarding opioid activity were greatly contrasting with previous findings. The results of this study make an important contribution to the growing body of literature on the prosocial consequences of behavioral synchrony. According to our findings, it seems sufficient to coordinate movements in reference to a shared beat to enhance cooperation among participants. Thus, strict synchronous movement does not seem to be essential. It is important to shed light on this particular issue as it may result in implications regarding music therapy and education policies, as music fulfills a great and prominent role in promoting the occurrence of temporal coordination. In addition to the pleasure music can bring, temporal coordination through musical group interaction may be beneficial in promoting generalized empathy and prosocial behavior.

References

Arai, H., Takenaka, K., & Oka, K. (2003). Ikkasei undou ni mochiiru kanjo shakudo: shakudo no kaihatsu to undou ji ni okeru kanjou no kentou (Development of scale to assess emotion while sports performance), Journal

of Health Psychology Research, 16, 1-10.

Aron, A., Aron, E. N., & Smollan, D. (1992). Inclusion of Other in the Self Scale and the Structure of Interpersonal Closeness. Journal

of Personality and Social Psychology, 63(4),

596–612. http://doi.org/10.1037/0022-3514.63.4.596

Baimel, A., Severson, R. L., Baron, A. S., & Birch, S. A. J. (2015). Enhancing “theory of mind”

through behavioral synchrony. Frontiers in

Psychology, 6, 1–6.

Baron-Cohen, S., Bowen, D. C., Holt, R. J., Allison, C., Auyeung, B., Lombardo, M. V., … Lai, M. C.

(2015). The “Reading the Mind in the Eyes” Test: Complete Absence of Typical Sex Difference in ~400 Men and Women with Autism. PLoS ONE, 10(8), 1–17.

http://doi.org/10.1371/journal.pone.01365 21

Baron-Cohen, S., Wheelwright, S., Hill, J., Raste, Y., & Plumb, I. (2001). The “‘Reading the Mind in the Eyes’” Test Revised Version: A Study with Normal Adults, and Adults with Asperger Syndrome or High-functioning Autism.

Journal of Child Psychology and Psychiatry, 42(2), 241–51.

http://doi.org/10.1111/1469-7610.00715 Bradley, M., & Lang, P. J. (1994). Measuring

Emotion: The Self-Assessment Manikin and the Semantic Differential. Journal of Behavior

Therapy and Experimental Psychiatry, 25(1),

49–59. http://doi.org/10.1016/0005-7916(94)90063-9

Brass, M., Bekkering, H., & Prinz, W. (2001). Movement observation affects movement execution in a simple response task. Acta

Psychologica, 106, 3–22.

Brown, S. (2000). Evolutionary models of music: From sexual selection to group selection. In F. Tonneau & N.S. Thompson (Eds.),

Perspectives in Ethology: Behavior, Evolution and Culture (pp. 231–281). New York, NY:

Plenum Publishers.

Catmur, C., & Heyes, C. (2013). Is It What You Do, or When You Do It? The Roles of Contingency and Similarity in Pro-Social Effects of

Imitation. Cognitive Science A

Multidisciplinary Journal, 37(8), 1541–1552.

http://doi.org/10.1111/cogs.12071

Cirelli, L. K., Einarson, K. M., & Trainor, L. J. (2014). Interpersonal synchrony increases prosocial behavior in infants. Developmental Science,

17(6), 1003–1011.

http://doi.org/10.1111/desc.12193

Cohen, C. (2015). Music: A Universal Language? In Urbain, O., Music and Conflict Transformation:

Harmonies and Dissonances in Geopolitics (pp.

26-39). New York, NY: IB Tauris. Cohen, E. E. A., Ejsmond-Frey, R., Knight, N., &

Dunbar, R. I. M. (2010). Rowers’ high: behavioural synchrony is correlated with elevated pain thresholds. Biology Letters, 6, 106–108.

http://doi.org/10.1098/rsbl.2009.0670 Cohen, E., Mundry, R., & Kirschner, S. (2014).

(14)

14

Religion, Brain & Behavior, 4(1), 20–30.

http://doi.org/10.1080/2153599X.2012.741 075

Cohen, J. (1988). Statistical Power Analysis for the

Behavioral Sciences (2nd_{ed.). Hillsdale, NJ:}

Erlbaum.

Cross, I., & Morley, I. (2009). The evolution of music: Theories, definitions and the nature of the evidence. In Communicative Musicality (pp. 61–82).

http://doi.org/papers://7EAF3440-77F6-4B89-B12D-846E31E57E4A/Paper/p3624 Cross, L., Wilson, A. D., & Golonka, S. (2016). How Moving Together Brings Us Together: When Coordinated Rhythmic Movement Affects Cooperation. Frontiers in Psychology, 7, 1–13. http://doi.org/10.3389/fpsyg.2016.01983 Curley, J. P., & Keverne, E. B. (2005). Genes, brains

and mammalian social bonds. Trends in

Ecology and Evolution, 20(10), 561–567.

http://doi.org/10.1016/j.tree.2005.05.018 Davis, M. H. (1983). Measuring Individual

Differences in Empathy: Evidence for a Multidimensional Approach. Journal of

Personality and Social Psychology, 44(1),

113–126. http://doi.org/10.1037/0022-3514.44.1.113

Demos, A. P., Chaffin, R., Begosh, K. T., Daniels, J. R., & Marsh, K. L. (2012). Rocking to the beat: Effects of music and partner’s movements on spontaneous interpersonal coordination.

Journal of Experimental Psychology: General, 141(1), 49–53.

http://doi.org/10.1037/a0023843 Dijksterhuis, A., & Bargh, J. A. (2001). The

perception-behavior expressway: automatic effects of social perception on social

behavior. Advances in Experimental Social

Domes, G., Heinrichs, M., Michel, A., Berger, C., & Herpertz, S. C. (2007). Oxytocin Improves “Mind-Reading” in Humans. Biological

Psychiatry, 61(6), 731–733.

http://doi.org/10.1016/j.biopsych.2006.07.0 15

Dunbar, R. I. M., Kaskatis, K., MacDonald, I., & Barra, V. (2012). Performance of Music Elevates Pain Threshold and Positive Affect: Implications for the Evolutionary Function of Music. Evolutionary Psychology, 10(4), 688– 702. http://doi.org/epjournal-2536 [pii] Eisenberg, N., & Miller, P. A. (1987). The Relation of

Empathy to Prosocial and Related Behaviors.

Psychological Bulletin, 101(1), 91–119.

http://doi.org/10.1037/0033-2909.101.1.91 Gallese, V., Keysers, C., & Rizzolatti, G. (2004). A

unifying view of the basis of social cognition.

TRENDS in Cognitive Sciences, 8(9), 396–403.

http://doi.org/10.1016/j.tics.2004.07.002 Ghasemtabar, S. N., Hosseini, M., Fayyaz, I., Arab, S.,

Naghashian, H., & Poudineh, Z. (2015). Music therapy: An effective approach in improving social skills of children with autism.

Advanced Biomedical Research, 4(157), 1–12.

http://doi.org/10.4103/2277-9175.161584 Gielen, P., Elkhuizen, S., van den Hoogen, Q., Lijster,

T., & Otte, H. (2014). De waarde van cultuur. Goldstein, A., & Grevert, P. (1978). Placebo

Analgesia, Endorphins, and Naloxone. The

Lancet, 2(8104), 1385.

Good, A., & Russo, F. A. (2016). Singing Promotes Cooperation in a Diverse Group of Children.

Social Psychology, 1–5.

http://doi.org/10.1027/1864-9335/a000282

Hayward, G. (2014). Singing as one: community in

synchrony (Unpublished doctoral

dissertation). University of Cambridge, Cambridge, United Kingdom.

Hove, M. J., & Risen, J. L. (2009). It’s All in the Timing: Interpersonal Synchrony Increases Affiliation. Social Cognition, 27(6), 949–960. http://doi.org/10.1521/soco.2009.27.6.949 Hurley, S. (2008). The shared circuits model (SCM ): How control, mirroring, and simulation can enable imitation, deliberation, and

mindreading. Behavioral and Brain Sciences,

31, 1–58.

Iversen, J.R., & Patel, A.D. (2008), The Beat Alignment Test (BAT): Surveying beat processing abilities in the general population. In: Proceedings of the 10th International Conference on Music Perception and

Cognition (ICMPC 10). Sapporo: Japan. p. 465. Keller, P. E., Novembre, G., & Hove, M. J. (2014).

Rhythm in joint action: psychological and neurophysiological mechanisms for real-time interpersonal coordination. Philosophical

Transactions of the Royal Society B, 369, 1–12.

http://doi.org/10.1098/rstb.2013.0394 Kniffin, K. M., Yan, J., Wansink, B., & Schulze, W. D.

(2016). The sound of cooperation: Musical influences on cooperative behavior. Journal

(15)

15 http://doi.org/10.1002/job

Kokal, I., Engel, A., Kirschner, S., & Keysers, C. (2011). Synchronized drumming enhances activity in the caudate and facilitates

prosocial commitment - If the rhythm comes easily. PLoS ONE, 6(11), 1–12.

Lakens, D. (2010). Movement synchrony and perceived entitativity. Journal of

Experimental Social Psychology, 46(5), 701–

708.

http://doi.org/10.1016/j.jesp.2010.03.015 Launay, J., Tarr, B., & Dunbar, R. I. M. (2016).

Synchrony as an Adaptive Mechanism for Large-Scale Human Social Bonding. Ethology, 779–789. http://doi.org/10.1111/eth.12528 Laurence, F. (2015). Music and Empathy. In Urbain,

O., Music and Conflict Transformation:

Harmonies and Dissonances in Geopolitics (pp.

13-24). New York, NY: IB Tauris.

Lindenberger, U., Li, S.-C., Gruber, W., & Müller, V. (2009). Brains swinging in concert: cortical phase synchronization while playing guitar.

BMC Neuroscience, 10(1), 1–12.

http://doi.org/10.1186/1471-2202-10-22 Martel, Frances L., et al. (1995). Effects of opioid receptor blockade on the social behavior of rhesus monkeys living in large family groups.

Developmental Psychobiology, 28(2), 71-84.

Miles, L. K., Griffiths, J. L., Richardson, M. J., & Macrae, C. N. (2010). Too late to coordinate: Contextual influences on behavioral

synchrony. European Journal of Social

http://doi.org/10.1002/ejsp

Miles, L. K., Nind, L. K., & Macrae, C. N. (2009). The rhythm of rapport: Interpersonal synchrony and social perception. Journal of

Experimental Social Psychology, 45(3), 585–

589.

http://doi.org/10.1016/j.jesp.2009.02.002 Müllensiefen, D., Gingras, B., Musil, J., & Stewart, L.

(2014). The Musicality of Non-Musicians: An Index for Assessing Musical Sophistication in the General Population. PLoS ONE, 9(2), 1– 23.

Müller, V., Sänger, J., & Lindenberger, U. (2013). Intra- and Inter-Brain Synchronization during Musical Improvisation on the Guitar.

PLoS ONE, 8(9), e73852.

Overy, K. (2012). Making music in a group: Synchronization and shared experience.

Annals of the New York Academy of Sciences, 1252(1), 65–68.

http://doi.org/10.1111/j.1749-6632.2012.06530.x

Overy, K., & Molnar-Scakacs, I. (2009). Being Together in Time: Musical Experience and the Mirror Neuron System. Music Perception:

An Interdisciplinary Journal, 26(5), 489–504.

http://doi.org/10.1525/rep.2008.104.1.92.T his

Rabinowitch, T.C. (2015). How, Rather Than What Type of, Music Increases Empathy. Empirical

Musicology Review, 10(1-2), 96–98. Retrieved

from

http://emusicology.org/article/view/4572\ nhttp://emusicology.org/article/download/ 4572/4079

Rabinowitch, T., Cross, I., & Burnard, P. (2012), Musical group interaction, intersubjectivity and merged subjectivity. In D. Reynolds & M. Reason (Eds.), Kinesthetic Empathy in

Creative and Cultural Practices (pp. 109–

120). Bristol, UK: Intellect Press.

Reddish, P., Bulbulia, J., & Fischer, R. (2014). Does synchrony promote generalized prosociality?

Religion, Brain & Behavior, 4(1), 3–19.

http://doi.org/10.1080/2153599X.2013.764 545

Reddish, P., Fischer, R., & Bulbulia, J. (2013). Let’s Dance Together: Synchrony, Shared

Intentionality and Cooperation. PLoS ONE,

8(8), 1–13.

Reddish, P., Tong, E. M. W., Jong, J., Lanman, J. A., & Whitehouse, H. (2016). Collective synchrony increases prosociality towards

non-performers and outgroup members. British

Journal of Social Psychology, 1–17.

http://doi.org/10.1111/bjso.12165 Rennung, M., & Göritz, A. S. (2016). Prosocial

Consequences of Interpersonal Synchrony: A Meta-Analysis. Zeitschrift Für Psychologie,

224(3), 168–189.

http://doi.org/10.1027/2151-2604/a000252

Sänger, J., Müller, V., & Lindenberger, U. (2012). Intra- and interbrain synchronization and

(16)

16 network properties when playing guitar in duets. Frontiers in Human Neuroscience, 6, 1– 19.

http://doi.org/10.3389/fnhum.2012.00312 Sebanz, N., Bekkering, H., & Knoblich, G. (2006).

Joint action: bodies and minds moving together. Trends in Cognitive Sciences, 10(2), 70–76.

http://doi.org/10.1016/j.tics.2005.12.009 Shamay-Tsoory, S. G., Aharon-Peretz, J., & Perry, D.

(2009). Two systems for empathy: A double dissociation between emotional and cognitive empathy in inferior frontal gyrus versus ventromedial prefrontal lesions.

Brain, 132, 617–627.

http://doi.org/10.1093/brain/awn279 Stein, E. (1989). On The Problem of Empathy (3rd

ed.). Washington, DC: ICS Publications. Stevens, J.P. (2009). Applied multivariate statistics

for the social sciences (5th_{ed). New York, NY:} Routledge.

Sullivan, P., Gagnon, M., Gammage, K., & Peters, S. (2015). Is the Effect of Behavioral Synchrony on Cooperative Behavior Mediated by Pain Threshold? The Journal of Social Psychology,

155(6), 650–660.

http://doi.org/10.1080/00224545.2015.107 1766

Sullivan, P. J., Rickers, K., & Gammage, K. L. (2014). The Effect of Different Phases of Synchrony on Pain Threshold. Group Dynamics: Theory,

Research, and Practice, 18(2), 122–128.

http://doi.org/10.1037/gdn0000001 Szymanski, C., Pesquita, A., Brennan, A. A., Perdikis,

D., Enns, J. T., Brick, T. R., … Lindenberger, U. (2017). Teams on the same wavelength perform better: Inter-brain phase synchronization constitutes a neural substrate for social facilitation. NeuroImage,

152, 425–436.

http://doi.org/10.1016/j.neuroimage.2017.0 3.013

Tarr, B., Launay, J., Cohen, E., & Dunbar, R. (2015). Synchrony and exertion during dance independently raise pain threshold and encourage social bonding. Biology Letters, 11, 1–4. http://doi.org/10.1098/rsbl.2015.0767 Tarr, B., Launay, J., & Dunbar, R. I. M. (2014). Music and social bonding: “self-other” merging and neurohormonal mechanisms. Frontiers in

http://doi.org/10.3389/fpsyg.2014.01096 Tarr, B., Launay, J., & Dunbar, R. I. M. (2015). Silent

disco: Dancing in synchrony leads to elevated pain thresholds and social closeness.

Evolution and Human Behavior, 37(5), 343–

349.

http://doi.org/10.1016/j.evolhumbehav.201 6.02.004

Trehub, S. E., Becker, J., & Morley, I. (2015). Cross-cultural perspectives on music and

musicality. Philosophical Transactions of the

Royal Society B, 370, 1–9.

http://doi.org/10.1098/rstb.2014.0096 Valdesolo, P., Ouyang, J., & DeSteno, D. (2010). The

rhythm of joint action: Synchrony promotes cooperative ability. Journal of Experimental

Social Psychology, 46(4), 693–695.

http://doi.org/10.1016/j.jesp.2010.03.004 Weinstein, D., Launay, J., Pearce, E., Dunbar, R. I. M.,

& Stewart, L. (2016). Singing and social bonding: Changes in connectivity and pain threshold as a function of group size.

Evolution and Human Behavior, 37(2), 152–

158.

http://doi.org/10.1016/j.evolhumbehav.201 5.10.002

Wiltermuth, S. S., & Heath, C. (2009). Synchrony and Cooperation. Psychological Science,

20(1), 1–5.

http://doi.org/10.1111/j.1467-9280.2008.02253.x

Wolf, W., Launay, J., & Dunbar, R. I. M. (2016). Joint attention, shared goals, and social bonding.

British Journal of Psychology, 107(2), 322–

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Supplementary Materials

1.1 Questionnaires

Social rapport

How connected do you feel with the other participant? (1 = not at all, 7 = very much) How similar do you feel to the other participant? (1 = not at all similar, 7 = very similar) How much do you trust the other participant? (1= not at all, 7 = very much)

How likeable is the other participant? (1 = extremely dislikeable, 7 = extremely likeable) How close do you feel to the other participant? (1 = not at all close, 7 = very close)

Translated Japanese mood assessment

Please indicate how closely the following states relate to you current mood (1 weakest, 5 = strongest) Negative dimension: Panicked Regrettable Reluctant Depressed Arousal dimension: Excited Fascinated Thrilled Impassioned Calm dimension: Relieved Easygoing Relaxed Chilled

Division of Reading the Mind in the Eyes task

Pre-Eyes: Q1-13, 16, 17, 19, 22, 23 Post-Eyes: Q14, 15, 18, 20, 21, 24 - 36

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1.2 Statistics

Normality testing and homogeneity of variance Shapiro-Wilk and Levenes’ tests indicated that the majority of the data was normally distributed with homogenous variance (see Table S1). Solely the Eyes post score was non-normally distributed. However, log transformations resulted in more non-normally distributed variables. Additionally, a reliable non-parametric of the mixed ANOVA was hard to find as the Friedman test (alternative for a Repeated Measures ANOVA) is only applicable if one group is measured on three or more different occasions. Taken this into consideration, a mixed ANOVA was performed.

To verify the results, a one-way ANOVA was performed with the change in Eyes score (post – pre) as dependent variable and the Goldsmith and IRI-PT as covariates. This analysis resulted in the same findings; no significant effect of drumming condition was observed on cognitive empathy scores (F(2, 30)= 2.44, p = .10). The assumptions of normality and homogeneity of variances were

met in this analysis.

Table S1 - P-values for Shapiro-Wilk normality test and Levene's test of homogenous variance on the

pre, post and change scores for the Eyes scores and pain threshold (nsynchrony = 13, ninteractional = 12,

nasynchrony = 10)

Dependent

variable Drumming condition Pre score (p-value) Post score (p-value) (p-value) Change

Homogeneity of variance of

change (p-value)

Reading the Mind in the Eyes

Synchrony .25 .04 .91 .37 Interactional synchrony .27 .10 .34 Asynchrony .46 .77 .39 Pain Threshold Synchrony .29 .89 .09 .36 Interactional synchrony .18 .28 .96 Asynchrony .21 .83 .79

Table S2 - P-values for Shapiro-Wilk normality test and Levene's test of

homogenous variance on the scores for the Prosocial Commitment measurement (Pencil Task) (nsynchronous = 4, ninteractional = 4, nasynchronous = 4)

Dependent

variable Drumming condition (p-value) Score

Homogeneity of variance (p-value) Prosocial Commitment Synchrony .27 .46 Interactional synchrony .97 Asynchrony .22

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Table S3 - Results for Mixed ANOVA of Japanese mood-arousal dimensions (n = 35) Sum of

Squares df Square Mean F p-value

Time point Calm 1.76 1 1.76 50 .49 Negative 5.54 1 5.54 3.82 .06 Arousal 31.88 1 31.88 15.00 > .01 Time point *Condition Calm 2.79 2 1.40 .39 .68 Negative 2.07 2 1.04 .72 .50 Arousal 3.36 2 1.68 .79 .46

Table S4 - Results for Mixed ANOVA of Self-Assessment Manikin’s valence and arousal levels (n = 35) Sum of

Squares df Square Mean F p-value

Time point Valence 650.80 1 650.80 6.21 .02

Arousal 3871.35 1 3871.35 23.40 > .01

Time point *Condition

Valence 151.64 2 75.82 .72 .49

Arousal 150.48 2 75.24 .46 .64

Table S5 - Results for Kruskal Wallis tests on the effect of drumming condition on various measures of

social rapport (n = 35) Chi-Square df p-value Change in connectedness 3.48 2 .18 Change in similarity 4.95 2 .08 Change in trust .14 2 .93 Change in likeness .14 2 .93 Change in closeness .33 2 .85

Change in self/other overlap 3.64 2 .16

Table S6 -Results for Kruskal Wallis tests on the effect of drumming condition on various measures of

participants’ experience of the experiment (n = 35)

Chi-Square df p-value

Perceived success 3.74 2 .69

Difficulty 2.01 2 .37