Interpersonal Synchrony & Music:
Consequences Regarding Social
Functioning of Children and Adults
Literature Thesis
MSc in Brain and Cognitive Sciences, Track Cognitive Science,
University of Amsterdam
Student: Jeannette van Ditzhuijzen (11116587) Number of ECTS: 12 ECTS
Date: January, 2017
Supervisor: Dr. Makiko Sadakata Co-assessor: Dr. Fleur Bouwer
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Content
1. Introduction
1.1 Interpersonal synchrony and social bonding 3
1.2 The current review 4
2. Interpersonal Synchrony through Music
2.1 Definitions of interpersonal synchrony 6
2.2 Rhythmic entrainment and beat perception 6
2.3 Connection between beat perception and motor areas in the brain 7
2.4 Summary 7
3. Development of Beat Perception, Rhythmic Entrainment and
Prosocial Behavior over Infancy
3.1 Beat perception: interplay of nature and nurture 9 3.2 Rhythmic entrainment and interpersonal synchrony in infants 10
3.3 Progression of prosocial behavior 11
3.4 Summary 12
4. Influence of Music in Interpersonal Synchrony
4.1 Minimized prediction error through music: simply making it easier
to synchronize 13
4.2 Shared experience of emotional engagement: at the group level 14 4.3 Arousal-mood hypothesis: at the individual level 14
4.4 Summary 15
5. Summary of Studies into Interpersonal Synchrony & Music
5.1 Interpersonal synchrony without music 16
5.2 Interpersonal synchrony accompanied with sound
5.2.1 Moving to metrical sounds 17
5.2.2 Behavioral synchrony in reference to rich musical songs 17 5.3 Active music making and behavioral synchrony
5.3.1 One moment of musical participation 19
5.3.2 One year of music making classes 20
5.4 Passive music listening without synchronous movement 22
5.5 Summary 23
6. Discussion
6.1 Main findings 24
6.2 Additional value of musical elements? 25
6.3 Underlying mechanisms regarding behavioral synchrony and
prosocial consequences 26
6.4 Future directions 28
6.5 Concluding remarks 28
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1. Introduction
Music, a trivial and universal feature of human culture, has seen a surge of interest in the recent decade of research. Particularly, whilst debating the importance of music in school curricula, examining far transfer effects of music education on academic achievement and general intelligence is considered a hot topic (Jaschke, Eggermont, Honing, & Scherder, 2013; Winner, Goldstein, & Vincent-Lancrin, 2013), in addition to studies tapping into the controversial Mozart
Effect (e.g. Rauscher, F. H., Shaw, G. L., & Ky, 1993). Moreover, to elucidate neural and behavioral
consequences of music training, imaging studies extensively compare individual brains of musicians with those of non-musicians regarding structural and functional differences (e.g. Norton et al., 2005; Schlaug, Norton, Overy, & Winner, 2005). Besides a growth in the field of research concerning the effects of musical training on intelligence and academic achievement, another area of music research is emerging, namely studies tapping into the social aspects of musical engagement, where music is considered as a social interaction (Trehub, Becker, & Morley, 2015). Consequently, the impact of music listening or performance in a group context is investigated, rather than the influence of one individual producing or listening to music.
The thought that music has a profound influence on a social group has old roots. Specifically, historical records and anthropological studies examining aspects of ancient cultural rituals (e.g. Guemple, 1971), suggest that group music making may originally evolved as a mechanism to establish and maintain social bonds in progressively larger groups (Weinstein, Launay, Pearce, Dunbar, & Stewart, 2016), ultimately increasing prosocial in-group behavior (Launay, Tarr, & Dunbar, 2016; Tarr, Launay, & Dunbar, 2014), suggesting an adaptive purpose of music in evolution (Good & Russo, 2016).
1.1 Interpersonal synchrony and social bonding
A possible underlying mechanism of music functioning as social glue, is the involvement of
interpersonal movement synchrony. People in all known cultures move their bodies in time to the
rhythm of the music, whether singing, drumming or dancing (Wallin & Merker, 2001; Phillips-Silver & Trainor, 2005), and according to Launay et al. (2016), interpersonal synchrony exploits existing neurobiological and psychological mechanisms important in social bonding.
Historian McNeill (1995) discusses the continuous prevalence of coordinated rhythmic movement in his book Keeping Together in Time: Dance and Drill in Human History, emphasizing the occurrence of behavioral synchrony in collective rituals ranging from religious ceremonies to sports cheering and army drill, as documented by anthropologists and historians. In his book, McNeill highlights the peculiar power of interpersonal synchrony in both creating and uniting human communities (McNeill, 1995). According to McNeill (1995), rhythmic muscular movement
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may result in an euphoric feeling, that arouses among participants as an visceral emotional response. This ultimately establishes a sense of community through a blurring of self-awareness
and the heightening of fellow-feeling with all who share in the dance (McNeill, p. 8, 1995), or other
activity involving shared movement.
Recent behavioral studies investigated a possible causal link between interpersonal synchrony and social bonding by letting adult participants walk, tap, run, sing or drum in synch, after which they were asked to execute a cooperative group task or social attitude questionnaire (e.g. Kokal, Engel, Kirschner, & Keysers, 2011; Kreutz, 2014; Wiltermuth & Heath, 2009), and indeed, the results seem to provide evidence in support of the hypothesis claiming a capacity of behavioral synchrony for social bonding. However, an important difference between these studies should be noted considering environmental cueing and the presence of music during the act of behavioral synchrony. While some experiments use no actual sound to induce coordinated movements (e.g. Tunçgenç, Cohen, & Fawcett, 2015; Valdesolo, Ouyang, & DeSteno, 2010), others employ an external pacesetter in the form of a simple metronome (e.g. Davis, Taylor, & Cohen, 2015; Tunçgenç & Cohen, 2016) or a rich musical song (e.g. Cirelli, Wan, & Trainor, 2014; Tarr, Launay, & Dunbar, 2015). Some authors even make subjects produce musical sounds by themselves by way of group singing or drumming (e.g. Good & Russo, 2016; Kirschner & Ilari, 2014; Kreutz, 2014), resulting in organized musical sounds as well as synchronized behavior through synchronization of laryngeal muscles in addition to the coordination facial and head movements, and respiratory patterns in the case of singing (Good & Russo, 2016).
1.2 The current review
The current review tries to disentangle the potential role of musical elements in social effects of behavioral synchrony across the lifespan, as music may positively influence the emotional state of participants (Dunbar, Kaskatis, MacDonald, & Barra, 2012; Kniffin, Yan, Wansink, & Schulze, 2016; Koelsch, 2013; Overy & Molnar-Scakacs, 2009), or possibly creates a situation in which the behavior of others can be better predicted (Overy & Molnar-Scakacs, 2009). Hence, this review tries to make a comparison between the social influences of synchronized body movements in mere silence, and the social effects of interpersonal synchrony through either passive or active music experience. Up till now, studies examined the effects of behavioral synchrony upon one age group at a time. However, in the current review all detected studies will be taken together and a comparison will be made between adults and children, thus, examining the developmental process of interpersonal synchrony.
In sum, the aim of the current review is to examine the empirically demonstrated effects of interpersonal synchrony on social functioning of children and adults, and investigate to what extent music serves an additional value to these potential effects. In order to investigate this
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particular issue, studies involving interpersonal synchrony and prosocial consequences were examined with regards to the following four categories: (1) interpersonal synchrony without sound support (e.g. synchronous tapping, walking, running, rowing), (2) interpersonal synchrony accompanied by sound in the form of a metronome, or a rich musical song (e.g. dancing), (3) active music participation involving interpersonal synchrony (e.g. singing, drumming) and (4) mere music listening without coordinated body movement.
To arrive at summaries of the studies regarding this distinction, definitions of interpersonal synchrony are clarified first and related to music, mainly by discussing the processes of beat perception and rhythmic entrainment. Given the fact that the current thesis partly focuses on children, the development of beat perception and rhythmic entrainment in infancy is considered, as well as the progression of prosocial behavior. Afterwards, hypotheses are proposed as to why music may serve an additional value in the process of interpersonal synchrony, thus going back to the main aim of the current thesis. Subsequently, summaries of studies regarding the aforementioned distinction are given. At last, the main findings are discussed along with potential underlying mechanisms regarding interpersonal synchrony and its prosocial consequences.
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2. Interpersonal Synchrony through Music
2.1 Definitions of interpersonal synchrony
Interpersonal synchrony entails instances when movements of two or more people overlap, occurring in-phase or anti-phase, although in-phase is the more stable mode (Ouwehand & Peper, 2015; Rennung & Göritz, 2016). A comparable process is mimicry, which refers to the imitation of action of others, however this differs from interpersonal synchrony by involving a time lag at times (Rennung & Göritz, 2016). According to Cacioppo et al. (2014), the same state of synchrony may be the result of one of three distinct production processes, namely (1) orchestration, when two or more individuals entrain their movements to an external pacesetter such as a metronome, (2) reciprocal entrainment, where individuals monitor each other and adjust their movement in response to their partners’ movement, and (3) unilateral entrainment, where one individual within a dyad regulates his or her movements in accordance with the movements of the other individual, also called the referent (Cacioppo et al., 2014). Within music research, some authors prefer to call the process of synchronization rhythmic entrainment (Ilari, 2016), where an individual aligns their motor actions to a regular beat (Merchant & Honing, 2014).
It should be clear that interpersonal synchrony and rhythmic entrainment are two different processes. Interpersonal synchrony involves actual movement similarity of two or more individuals, whereas rhythmic entrainment refers to the synchronization of an individual to a regular pulse. Thus, rhythmic entrainment is rather a production process resembling orchestration, possibly resulting in interpersonal synchrony when two or more people are present.
Finally, when considering the varieties in establishing behavioral synchrony, a distinction can be made regarding the presence and absence of musical elements. Where reciprocal and unilateral entrainment make no use of auditory cueing, orchestration and rhythmic entrainment do. Subsequently, it can be argued that interpersonal synchrony can occur with or without musical elements, resembling the main comparison made in the current review.
2.2 Rhythmic entrainment and beat perception
Rhythmic entrainment follows from the cognitive skill termed beat perception (Honing, 2012); the ability to perceive temporal regularity in a musical rhythm (Bouwer, Werner, Knetemann, & Honing, 2016), in other words, the capacity of humans to sense the beat. In able to perceive this temporal regularity, future beats in a rhythmic sequence of temporal intervals need to be predicted, meaning that the beat sensed by the listener, encompasses a series of regularly recurring psychological events, arising in response to a musical rhythm (Cooper & Meyer, 1960; Leow & Grahn, 2014). Thus, beat perception is not simply a stimulus property, it is an actual
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psychological response to a rhythm (Leow & Grahn, 2014), as the rhythm evokes a particular
regular pattern in the listener (Honing, p. 85, 2012). The tendency for humans to anticipate on
temporal regularity is also confirmed by tapping studies (see Repp, 2005) where human taps tend to precede the actual onset of stimuli, indicating that participants really expect beats in rhythmical stimuli (Repp & Su, 2013). Moreover, beat perception seems to be engaged almost automatically when listening to a metrical structure, as it is possible even when attention is not directly focused towards the rhythm (Bouwer et al., 2016).
2.3 Connection between beat perception and motor areas in the brain
The ability to feel and interpret the strong and weak patterns allows people to move and dance in time (Phillips-Silver & Trainor, p. 1430, 2005). When a person is listening to music, he or she often
spontaneously starts to synchronize body movements to the perceived beat either in forms of isolated movements such as clapping their hands or tapping their foot, or entire body movements are generated in accordance to the musical rhythm, as happens with dancing or jumping (Schaefer & Overy, 2015). This ability of humans to naturally synchronize movement with a steady beat has been shown in a range of conditions (Overy, 2012; Tranchant, Vuvan, & Peretz, 2016), and recent neuroscientific research has begun to clarify particular underlying mechanisms. Affirmatively, findings suggest that motor regions of the brain are strongly involved in the detection of pulse and the coupling of action and perception, indicating a link between auditory rhythm perception and motor responses (Schaefer & Overy, 2015).
For instance, functional magnetic resonance imaging (fMRI) studies indicate that merely listening to music activates motor regions such as the basal ganglia, mid-premotor cortex, supplementary motor area and cerebellum (Chen, Penhune, & Zatorre, 2008; Grahn & Brett, 2007). In addition, when entraining movement to musical sounds, cerebellar activity seems to be increased, relative to the situation where someone carries out the same movements without accompanying sound (Brown, Martinez, & Parsons, 2006; Schaefer, Morcom, Roberts, & Overy, 2014). At last, studies by Chen et al. (2008, 2006) suggest that the superior temporal gyrus is involved in beat perception, whilst the dorsal premotor cortex may present the integration of auditory stimuli with temporally organized motor actions, in other words, the dorsal premotor cortex seems to be involved in the process of rhythmic entrainment or synchronization (Chen et al., 2008, 2006). Taking together, this evidence suggests the existence of a natural link between auditory and motor systems (Chen et al., 2008).
2.4 Summary
Interpersonal synchrony can be the result of several processes, such as orchestration, reciprocal entrainment and unilateral entrainment. Rhythmic entrainment is a term used by research in the
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field of music, resembling the process of orchestration. Beat perception is a cognitive skill that plays an important role when entraining movement with a musical rhythm, as it involves the prediction of temporal regularities. The existence of a natural link between auditory and motor systems is being confirmed by several neuroimaging studies, potentially explaining the underlying mechanism of our natural and almost automatic body responses to regular beat in music. Therefore, when listening to music, we almost automatically sense the beat and frequently anticipate on the temporal regularity through body movements, making music a powerful manner to establish interpersonal synchrony.
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2. Development of Beat Perception, Rhythmic Entrainment and
Prosocial Behavior over Infancy
The current review examines the developmental process of interpersonal synchrony, by comparing adult studies to children studies. However, when children are seeking to synchronize through music, both beat perception and rhythmic entrainment need to have developed and stabilized. Therefore, in this chapter the development of beat perception and rhythmic entrainment, as well as the progression of prosocial behavior, are examined in more depth.
3.1 Beat perception: interplay of nature and nurture
According to Honing (2012), beat perception is a fundamental musical trait, possibly with an innate nature. Honing’s argument derives from electroencephalography (EEG) evidence suggesting that newborns, with a gestational age of 37-40 weeks, are already able to extract a regular beat from a varying rhythmic stimulus (Honing, 2012; Winkler, Háden, Ladinig, Sziller, & Honing, 2009). In these studies (Honing, 2012; Winkler et al., 2009), a typical 2-measure drum rock pattern was played while newborns were sleeping, however, beats were occasionally omitted from the rhythmical sequence. The obtained results suggested that the newborns were sensitive to the difference between rhythms with or without ‘downbeats’, which reflects the strongest beat in a metrical pattern (Honing, Bouwer, & Háden, 2014), suggesting that newborns can already perceive some regularity in temporal patterns.
However, even though beat perception might be present at birth, the development of our sensitivity for a metrical structure is most likely influenced by experience (Trainor & Cirelli, 2015). A study by Hannon & Trehub (2005a) shows for instance how musical exposure may shape perceptual abilities. Here, North American adults and infants, as well as Macedonian adults, listened to folk melodies with simple and complex metrical structures and consequently rated structure-preserving and structure-violating alterations of the original metrical structure regarding their consistency. The findings indicated that North American adults were only able to discriminate structure-violating variations from structure-preserving alterations in simple metrical contexts, whereas Bulgarian and Macedonian adults were able to differentiate them in both simple and complex metrical context. Interestingly, North American infants, seemed to perform similar to the Bulgarian and Macedonian adults. According to the authors, these results indicate that temporal perception and production abilities are influenced by musical enculturation, given the dominance of simple ratios in Western music (Hannon & Trehub, 2005). Not only music exposure may influence the perception of regularity, body movement seems to occupy an important role within rhythm perception of human infants as well (Phillips-Silver & Trainor, 2005). Particularly, rhythm perception of 7-months-olds is influenced by the way
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babies are bounced to the music played; infants appeared to prefer rhythmical patterns with accented beats that resembled the beats to which they were bounced, with either duple or triple form (i.e. march or waltz) (Phillips-Silver & Trainor, 2005). Not only do these findings suggest that experience influences beat perception, the existence of a link between motor and auditory domains, as suggested in the aforementioned fMRI studies in adults, is implicated in infancy as well (Trainor & Cirelli, 2015).
3.2 Rhythmic entrainment and interpersonal synchrony in infants
Whilst the ability to perceive a regular pulse in rhythmical patterns is suggestively observed in newborns already, actual signs of rhythmic engagement with stimuli appear around the age of 5 months (Zentner & Eerola, 2010). Even though this rhythmic engagement does seems to be modulated by the tempo of the auditory stimulus, where a faster auditory tempo resulted in faster movements, there is no clear evidence for definite movement-to-music synchronization, which is likely due to immature motor control in infants (Zentner & Eerola, 2010).
However, there is no clear consensus concerning the full development of movement-to-music synchronization. For example, Provasi & Bobin-Bègue (2003) suggest that a stable spontaneous motor tempo is established at the age of 2½, while others found that 4- and 5-year-olds still have poor synchronization skills (McAuley, Jones, Holub, Johnston, & Miller, 2006). However, this difference can possibly be explained by the presence of visual feedback in Provasi & Bobin-Bègue (2003), that encouraged children to pay attention to the auditory stimuli and therefore reinforced their synchronized taps, thus, helping children to show better synchronization skills. Moreover, both studies (McAuley et al., 2006; Provasi & Bobin-Bègue, 2003) examined the development of movement coordination in response to nonhuman external stimuli, whilst children with an age between 2½ and 4½ years seem to synchronize more accurately when they have to coordinate their movements with a drumbeat produced by an actual person than with one produced by a virtual partner (Kirschner & Tomasello, 2009). Therefore, rhythmic entrainment of children to auditory stimuli seems to stabilize at a later age than actual interpersonal synchrony through music participation.
Endedijk et al. (2015) examined the development of interpersonal synchrony through music participation by letting dyads of 2- to 4-year-olds drum together; one child would initiate drumming and the other followed. Their findings indicate that older children were better at coordinating their drumming behavior with a peer than younger children, even though children of all age groups showed similarly stable drumming patterns (Endedijk et al., 2015). This means that 2- and 3-year-olds do have the ability to produce a steady drumbeat, however, they do not adapt their produced drum rhythm to the rhythmic structure of their partner’s drumming, as 4-year-olds do (Endedijk et al., 2015). This finding is in accordance with Trainor & Cirelli (2015),
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who argue that robust rhythmic entrainment and interpersonal synchrony starts to present by the age of four.
Clearly, individual differences exist regarding the ability of rhythmic synchronization. Evidence has been found supporting a positive link between musical experience and beat synchronization, meaning that individuals with musical experience overall show enhanced synchronization skills when compared to individuals without musical experience (Drake, Jones, & Baruch, 2000; Thompson, White-Schwoch, Tierney, & Kraus, 2015). Others suggest a potential role of culture in the accuracy of entrainment, since Brazilian babies and preschool children on average exhibit higher means for spontaneous rhythmic entrainment than European children (Ilari, 2015; Kirschner & Ilari, 2014). These findings indicate some cultural variation, however the results could also be explained by active musical experience in group context (Kirschner & Ilari, 2014). More cross-cultural research is necessary to shed more light on the potential role of culture in the development of rhythmic entrainment.
3.3 Progression of prosocial behavior
In order to actually influence prosocial behavior through interpersonal synchrony, certain perceptual and behavioral processes involved in social behavior need to be developed as well. Therefore, the development of prosocial behavior, and influencing factors such as empathy and self-similarity, will be discussed in more detail in the following section.
Prosocial behavior can be grouped into the following distinct categories, namely sharing, helping and cooperative behavior (Marion, 2003), and these types of behaviors can be influenced by the concept of self-similarity amongst others (Mahajan & Wynn, 2012). In adults, there is a general tendency to prefer similar others (Brewer, 1979), towards whom they subsequently show stronger engagement in acts of great cooperation and support, relative to people dissimilar to them (Mahajan & Wynn, 2012). Mahajan & Wynn (2012) explored this development of preference for similarity in 11-months-old infants and demonstrated that these infants already assess others on the basis of similarity to their self, and affirmatively, infants seem to prefer more similar others to those less similar (Mahajan & Wynn, 2012). In addition, 12-months-olds also seem to show a preference for synchronizing others in comparison to asynchronously moving others, at least, if they are social entities (Tunçgenç et al., 2015). Thus, prosocial attitudes seem to be influenceable at the end of the first year of life.
Actual signs of prosocial behavior start to expose in the second year of life (Dunfield, Kuhlmeier, O’Connell, & Kelley, 2011), although the progression of the different forms of prosocial behavior does seems to vary (Dunfield, 2014). A study by Warneken & Tomasello (2007) for instance implies that children at an age of 14 months understand another’s unfulfilled goal and consequently helps him or her to achieve it, without receiving a reward. Cooperative skills on the
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other hand are only rudimentarily present at this age, possibly due to the fact that cooperation requires the ability to form and execute a shared goal, whereas helping someone else merely entails the understanding of what another individual aims to do (Warneken & Tomasello, 2007). The other category of sharing seems to emerge later in the second year of life (Brownell, Svetlova, Anderson, Nichols, & Drummond, 2013).
Not only self-similarity may have prosocial consequences, many authors argue that empathy is of essential importance in human altruistic behavior as well (Fukui & Toyoshima, 2014; Rabinowitch, Cross, & Burnard, 2012). This is also observed in early childhood, where empathic concern seems to be associated with prosocial behavior (Roth-Hanania, Davidov, & Zahn-Waxler, 2011; Williams, O’Driscoll, & Moore, 2014). Empathy has both emotional and cognitive dimensions, although these can be experienced separately. Affective empathy involves the capacity to experience another’s emotional states and respond sympathetically, whereas cognitive empathy refers to the ability to understand others’ perspectives (van Lissa et al., 2014). According to Roth-Hanania et al. (2011), both affective and cognitive markers of empathy for another in distress, are already evidenced in 8- and 10-month-olds, additionally, these levels of empathy also seem to predict prosocial behavior towards distressed mother observed in the second year of life (Roth-Hanania et al., 2011).
3.4 Summary
Even though immature motor control limits the ability of infants to actually entrain movement to a rhythm, their spontaneous movements are to some extent affected by the tempo of the music. The ability to perceive regularity in temporal patterns seems to be present at birth, although sensitivity for a metrical structure, as well as mere rhythmic entrainment skills, seem to be influenced by experience. Solid interpersonal synchrony through music participation starts to exhibit at the age of four, whilst individual movement synchronization to an auditory stimulus seems to stabilize at later age. Possibly, this indicates that younger children may benefit more from actual interpersonal synchrony established via active music participation (e.g. drumming), than through passive music participation (e.g. dancing), given the earlier maturity of active music participation involving behavioral synchrony. At last, self-similarity and the development of empathy are suggested to be important factors influencing prosocial behavior, which start to emerge during the second year of life.
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4. Influence of Music in Interpersonal Synchrony
Behavioral research has suggested that adults who synchronize their steps together whilst walking, in the absence of an external pacesetter, ultimately display more cooperative behavior (Wiltermuth & Heath, 2009). As stated in the introduction, the main goal of the current thesis is to examine whether music may serve an additional value in this type of process. What would have been the outcome of Wiltermuth & Heath's (2009) study if subjects were presented with a musical song whilst walking, or, what if the participants sung a song in synchrony. Would there have been a difference in the outcome regarding the degree of prosocial behavior? In the following section several hypotheses are proposed as to why particularly music may serve an additional value in the process of interpersonal movement synchrony.
4.1 Minimized prediction error through music: simply making it easier to synchronize
The most self-evident hypothesis why music may strengthen potential effects of behavioral synchrony lies in the fact that a musical song can act as an external pacesetter, inclined to increase synchrony accuracy, even when compared with synchronizing to a mere metronome beat (Tranchant et al., 2016). Specifically, when a group of individuals synchronize their movements to the same musical beat, an environment is created in which the behavior of others can be better predicted, described by Overy & Molnar-Scakacs (2009) as an environment of minimized
prediction error (Schaefer & Overy, 2015).
Not only does a musical rhythm facilitate movement synchronization by diminishing prediction errors, additionally, musical features, may have a motivating influence on movement performance as observed in sports (Fritz et al., 2013; Simpson & Karageorghis, 2006), possibly by reducing perceived exertion (Fritz et al., 2013). Especially, perceived sense of exertion during exhaustive physical activity seems to be reduced when subjects experience actual musical agency (i.e. sound production driven by movements of the participant), in comparison to passively listening to music whilst working out (Fritz et al., 2013), suggesting that active music participation is likely associated with greater endorphin release than mere music listening (Launay et al., 2016).
Therefore, adding a musical rhythm or agency might make it easier, more motivating and less exhausting for individuals to get in synch with each other as they can predict better what is coming. Moreover, since the experience of successful interaction during synchronization seems to influence cooperative behavior in an economic game (Launay, Dean, & Bailes, 2013), enhancement of synchrony accuracy may be associated with an increase in prosocial behavior.
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4.2 Shared experience of emotional engagement: at the group level
Not only does a musical situation results in an enhancement of accurate movements which subsequently may influence social functioning, musical practices might also create a sense of affiliation through sharing an intense emotional experience (Overy & Molnar-Scakacs, 2009).
It is widely known that music has the ability to affect emotion and mood, perchance eliciting stronger responses than everyday feelings and emotions (Fukui & Toyoshima, 2014). However, in the case of social interaction, this emotional engagement is shared with others, making the experience even more valuable regarding social relations among participants (van Maanen, 2009). Particularly, passive and active music participation can automatically engage
social cognition and co-pathy (Koelsch, 2013), where the former refers to mental state attribution
(i.e. attempting to understand the intentions of the composer or other group members whilst producing music), and the latter means that inter-individual emotional states become more homogenous (Koelsch, 2013). According to Koelsch (2013), co-pathy derives partly from a process called emotional contagion, meaning that emotional states are transferred among people (Davies, 2013), indicating that a musical experience may be described at the emotional contagion level of the emotional response (Overy & Molnar-Scakacs, 2009). This has important implications since positive emotional contagion in turn seems to have prosocial influences (Barsade, 2002). Barsade (2002) for instance suggested that group members experiencing positive emotional contagion subsequently showed improved cooperation and decreased conflict.
Therefore, during a musical group experience there is not only movement synchrony enhancing interpersonal affiliations, additionally, a level of emotional contagion between group members is induced which in turn has potential prosocial consequences.
4.3 Arousal-mood hypothesis: at the individual level
Even though the arousal-mood hypothesis (Husain, Thompson, & Schellenberg, 2002) originally stems from research into the controversial Mozart Effect, which implies that music listening positively influences general intelligence, and specifically spatial temporal abilities, by indirectly affecting mood and arousal levels (e.g. Cassity, Henley, & Markley, 2007; Thompson, Schellenberg, & Husain, 2001), the hypothesis may also be applicable in the effect of music on social behavior. In general, when someone is in a positive mood, he or she has the tendency of helping others, according to the Feel good - Do good phenomenon (e.g. Isen & Levin, 1972). Accordingly, studies suggest that a positive mood at work is associated with a positive enhancement of work-related behaviors such as helping co-workers (e.g. George & Brief, 1992).
Kniffin, Yan, Wansink, & Schulze (2016) investigated the arousal-mood hypothesis in light of music listening and cooperative behavior. Here, subjects listened to a musical song, differing in valence, followed by an economical group exercise indicating cooperation (from Wiltermuth &
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Heath, 2009). Their outcomes suggested that cooperative behavior was positively influenced by listening to music comprising positive valence relative to music with a negative valence. In addition, mood seemed to be associated with performance (Kniffin et al., 2016). Other studies suggest that listening to music which involves a high feeling of groove seems to elicit more accurate entrainment in comparison to low-groove music listening (Janata, Tomic, & Haberman, 2012; Tranchant et al., 2016). Nevertheless, these results could also be explained by the arousal-mood hypothesis since perceived groove is associated with a sense of enjoyment and pleasure (Janata et al., 2012). Not only do we passively listen to music to regulate and arouse emotional responses, active music making may also result in elevated positive affect, by triggering the release of endorphins (Dunbar, Kaskatis, et al., 2012).
To conclude, musical experiences have the ability to affect arousal and mood levels, either via passive listening or active music making. In turn, it is hypothesized that a positive influence on emotional states may have prosocial consequences, as predicted by the arousal-mood hypothesis.
4.4 Summary
By adding music to an experience involving interpersonal synchrony, an environment of minimized prediction error is created, enhancing synchrony accuracy. In addition, music is capable of evoking exceptionally strong emotions and affecting the mood of individuals. These emotional states may even transfer amongst group members, resulting in homogenous mental states. Taken together, the elements of successful interaction, positive mood as well as positive emotional contagion through music may consequently positively influence social functioning towards other group members. Through these described processes, the addition of music may have prosocial consequences above those generated by mere movement symmetry.
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5. Summary of Studies into Interpersonal Synchrony & Music
In the following section, studies will be discussed examining interpersonal synchrony in light of social functioning. At first, a summary is given of studies examining mere behavioral synchrony, therefore, not accompanied by sound. Secondly, the addition of music listening is investigated where studies using an auditory metronome or musical song are discussed. Thirdly, active music participation is examined and at last studies are discussed involving mere music listening without coordinated body movements. In every section, children studies will be considered first, followed by an examination of adult findings.
5.1 Interpersonal synchrony without music
So far, only one study has been published that investigated synchronous movement without the support of any musical sound in children: Rabinowitch & Knafo-Noam (2015) found that synchronous vs asynchronous finger tapping of 8 year old children (steered by a visual of a bouncing ball), positively affected feelings of closeness, and in particular, perceived similarity to their interacting partner, with whom they were unacquainted before the experiment. Whether an increase in perceived similarity in turn led to more prosocial behavior, was not tested however.
Thus, this finding indicates that mere movement synchronization in reference of a visual metronome, may already lead to increased affiliative feelings amongst children. Moreover, this implies no distinct influence of synchronization accuracy, since the variability of synchronization accuracy is typically greater with visual than with auditory metronomes (Repp & Su, 2013).
Wiltermuth and Heath (2009) are one of the most cited authors when arguing that interpersonal synchrony promotes cooperation in adults. Their results suggest that groups of students walking together synchronously, without any sound support, out-cooperated groups walking asynchronously in economical group exercises (Wiltermuth & Heath, 2009). Others confirmed this hypothesis by suggesting that synchronous treadmill running (Sullivan et al., 2015), and chair rocking (Valdesolo et al., 2010), significantly impacted cooperative behavior among adults as well.
Nevertheless, when investigating prosocial consequences of rowing in adults, a sport extremely demanding in interpersonal synchrony, no direct evidence for a beneficial effect on group functioning has been found yet (Cohen et al., 2010; Davis et al., 2015; Sullivan & Rickers, 2013), contrasting previous results. Notably, pain threshold did seem to be elevated by synchronous group rowing in comparison to asynchronous rowing (Cohen et al., 2010; Sullivan & Rickers, 2013), which is interesting as pain threshold has been inferred as an indicator of endorphin activity (Dunbar, Baron, et al., 2012), and in turn, of feelings of social bonding (Shultz & Dunbar, 2010; Sullivan et al., 2015). However, Sullivan et al. (2015), examined the latter
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statement and argued that an elevated pain threshold actually has no mediating role in the effect of synchrony on cooperation, at least whilst running (Sullivan et al., 2015).
5.2 Interpersonal synchrony accompanied with sound
5.2.1 Moving to metrical sounds
A recent children study by Tunçgenç and Cohen (2016), examined the effects of (a)synchronous movement sets on both in- and out-group bonding, using mere metrical sounds in the form of drumbeats. Here, children with an age between 7 and 8 years, were assigned to groups which were emphasized by wearing color-coded group vests, consequently resulting in in-group favoritism. However, after a manipulation phase consisting of interpersonal synchrony, in comparison to non-synchronous movement, with the opposing group, out-group bonding significantly increased. Remarkably, the difference in bonding with the in-group relative to out-group disappeared after synchronous movement, suggesting that interpersonal synchrony steered by mere metrical sounds can affect prosocial attitudes in children.
Launay et al. (2013) claim that adults synchronizing to sound alone, in the absence of another person, is sufficient to induce feelings of trust as well. However, Hove & Risen (2009) suggest that synchronous finger tapping only increases adults’ affiliation when there is actual
interpersonal synchrony. Adult studies of Reddish et al. (2014, 2013, 2016) confirm Hove & Risen
(2009) findings, as synchronous group performance of simple body movements, accompanied by a metronome beat, positively affect willingness to help (Reddish et al., 2016) as well as prosocial behavior by way of an economical group exercise (Reddish et al., 2014). In addition, their findings suggests that this effect even extends beyond the adults’ performance group, therefore supporting generalized prosociality (Reddish et al., 2014, 2016).
5.2.2 Behavioral synchrony in reference to rich musical songs
When looking at the combination of movement synchrony and passive music listening, dancing is probably one of the first forms of movement that comes to mind. A total of two studies was found that systematically examined the possible impact of a dancing session on social functioning of high school children (Tarr, Launay, Cohen, & Dunbar, 2015; Vermeulen & Weijkamp, 2012). Tarr et al. (2015) manipulated synchrony as well as exertion, by performing either full body movements or solely small hand gestures in or out of synchrony. Their findings suggested that both manipulative measures positively, and independently, affected self-reported social bonding towards fellow participants as well as pain threshold (Tarr et al., 2015), resembling findings of Tunçgenç & Cohen (2016) using a mere metronome. However, both Tarr et al. (2015) and Tunçgenç & Cohen (2016) only assessed self-reported measure of social bonding, disabling the possibility to make statements on the effects of dancing on actual cooperative or prosocial behavior of children.
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Vermeulen & Weijkamp (2012) did take a measure of cooperative behavior into account and interestingly separated behavioral synchrony into two discrete aspects concerning motoric and rhythmic resemblance. Outcomes suggested that solely rhythmic equality positively affected cooperative behavior of high school children, meaning that the performed movements not necessarily have to be identical, whereas social identification and entitativity perceptions (perceiving the group as a unit) were only positively influenced when there was both rhythmic as well as motoric resemblance amongst individuals. In other words, children’s group perceptions seem to actually benefit from interpersonal synchrony accompanied by music, whilst children’s cooperative behavior benefits when a group of individuals merely adjust their movements to the musical rhythm (Vermeulen & Weijkamp, 2012).
The latter finding of Vermeulen & Weijkamp (2012) is also confirmed by infant studies (Cirelli, Einarson, & Trainor, 2014; Cirelli, Wan, & Trainor, 2016; Cirelli, Wan, et al., 2014). 14-month-olds who were bounced synchronously with an upstanding bouncing experimenter, either in-phase or anti-phase, were namely more likely to help the experimenter (Cirelli, Einarson, et al., 2014), or an affiliative of the experimenter (Cirelli et al., 2016), than a neutral stranger with whom they did not experience synchronous movement (Cirelli, Wan, et al., 2014). In sum, these results (Cirelli, Einarson, et al., 2014; Cirelli et al., 2016; Cirelli, Wan, et al., 2014; Vermeulen & Weijkamp, 2012) suggest that mere rhythmic equality, where two or more subjects move to the same beat without the movements being identical (e.g. crowd dancing to the same beat at a music festival), drives the effect of in-group prosocial behavior of children. However, in order to influence children’s prosocial attitudes, a combination of rhythmic and movement symmetry seems necessary, thus performing the exact same movements to the same beat (e.g. dance lesson) (Vermeulen & Weijkamp, 2012), suggesting an additive value of movement symmetry in social identification and perceptions of entitativity.
Findings of Endedijk et al. (2015) regarding prosocial attitudes of children can be observed in adults as well (Demos, Chaffin, Begosh, Daniels, & Marsh, 2012; Tarr, Launay, & Dunbar, 2015), as synchronous dancing or rocking in chairs seems associated with increased feelings of social closeness (Demos et al., 2012; Tarr et al., 2015) and elevated pain threshold (Tarr et al., 2015), in comparison to asynchronous dancing or chair rocking. However, interestingly, adults did not show subsequent increased cooperative behavior in an adapted version of the economical game used by Wiltermuth & Heath (2009) (Tarr et al., 2015). According to the Tarr et al. (2015), this suggests that dance encourages social bonding among co-actors by stimulating the
production of endorphins, but may not make people more altruistic (Tarr et al., p. 343, 2015). These
findings contrast outcomes of studies using no sound support, as well as children studies implementing sound, indicating no additive value of passive music listening during interpersonal synchrony in adults’ prosocial behavior.
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5.3 Active music making and behavioral synchrony
5.3.1 One moment of musical participation
Most recently, Good & Russo (2016) looked into the effect of synchronized singing on children by comparing cooperative behavior of children with an age between 6 and 11 years old, whom either participated in a 30 minutes singing session, a visual art activity or a group game session. Their results confirmed the hypothesis that behavioral synchrony promotes cooperation, since group singing, involving interpersonal synchrony, resulted in the highest cooperation scores. However, their findings give no insight into the question whether musical features serve an additional value in the effect of synchronized behavior as only the singing session involved actual synchronous behavior.
Kirschner & Tomasello (2010) measured social effects of a short session of joint music making on 4 year old children, by assigning 48 unacquainted dyads to either a music or non-musical condition. In both conditions, children collaborated in an interactive game together with the experimental instructor, sharing the same intentions, and receiving the same instructions to follow and imitate the instructors action, therefore, creating a sense of synchronization through joint action in both conditions. Outcomes indicated that children from the musical condition significantly showed more helpful and cooperative behavior towards their interacting partner than children from the non-musical condition. However, as the experimental instructor was not blind for the hypothesis in this study, the results can also be related to experimenter effects. Otherwise, these results may be explained by a situation of minimized prediction error in the musical condition (see section 4.1), which consequently enhanced synchronization accuracy and in turn resulted in greater prosocial consequences.
However, findings of Kirschner & Ilari (2014) contrast this line of thought, as Brazilian preschool children, who seem to drum more accurately with an interacting partner than children from Germany, show no significant difference in their prosocial tendencies towards their drumming partner in comparison to German children (Kirschner & Ilari, 2014). This suggests that the degree and accuracy of synchronization has no direct impact on willingness to share and help interacting others.
In addition, Kirschner & Ilari (2014) compared joint drumming with an experimenter versus drumming along a recorded beat. However, contrarily, no differences in children’s prosocial tendencies were observed between conditions (Kirschner & Ilari, 2014). Possibly, the results can be explained by the presence of a game in combination with the movement of drumming during both conditions, as this situation considerably resembles the musical condition of Kirschner & Tomasello (2010). Taking together, combining an element of play and active music participation is influential regarding prosocial consequences in children.
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Regarding adult studies, the earlier mentioned article by Wiltermuth & Heath (2009) not only involved an experiment incorporating synchronous walking, but also involved other experiments where students sang, or sang and simultaneously moved cups synchronously or asynchronously. They found that both conditions fostered cooperation and social contributions in adults (Wiltermuth & Heath, 2009), indicating that mere synchronization via singing suffices the promotion of cooperation in adults and gross physical synchrony is not necessary.
Others indicated a beneficial effect of choral singing on social closeness of adults as well, in comparison to other engaging activities such as a social conversation (Kreutz, 2014), crafts and creative writing (Pearce, Launay, MacCarron & Dunbar, 2016), even when these choral groups are larger than 150 people (Weinstein et al., 2016). In addition, Cohen, Mundry, & Kirschner (2014) showed a positive effect of synchronized drumming on connectedness and trust, however, without affecting subsequent cooperative behavior, contrary to results of Kokal et al. (2011). Cooperation was, on the other hand, affected by religious priming in comparison to secular priming, indicating a link between religion and prosociality (Cohen et al., 2014). However, according to Fischer, Callander, Reddish, & Bulbulia (2013), it is not merely sacred values that enhances cooperative behavior, but it is particularly the combination of sacred values and synchronous body movement that evokes prosociality behavior, as interpersonal synchrony modulates sacred values through feelings of entitativity, which subsequently may have prosocial consequences (Fischer et al., 2013).
In sum, collective singing seems to have prosocial consequences in both attitude and behavior of adults. Synchronous drumming, on the other hand, only influences social attitudes, if not combined with sacred values, indicating domain specific processes regarding various forms of active music participation.
5.3.2 One year of music making classes
Whilst Kirschner & Ilari (2014), Kirschner & Tomasello (2010) and Good & Russo (2016) investigated the potential influence of a single musical session in children, others examined the social effects of music interventions on children (Gerry et al., 2012; Goldstein & Winner, 2012; Rabinowitch et al., 2012; Schellenberg et al., 2015; Schellenberg, 2004; Trainor et al., 2012). Gerry et al. (2012) even investigated the social influence of music interventions on infants with a mean age of 6 months, who were randomly assigned to either active participatory or passive music classes. After 6 months of weekly classes, infants in the active condition showed larger increases on measures of positive affect and soothability, in addition to larger decreases on measures of distress and wariness of novelty, relative to the infants in the passive music classes. However, it should be noted that the parents in the passive condition did not receive specific instructions regarding observation techniques and subsequent reporting, as did the participants in the active
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class. This may explain the observed outcome, especially since the results depend on parent reports. Thus, even though the results suggest that active music interventions, relative to passive music classes, positively influence social behavior of infants, methodological weaknesses of the study disable the ability to draw firm conclusions.
Other researchers examined the influence of active music participation at school in middle childhood. A study by Schellenberg et al. (2015) for instance investigated an established music program called ‘Ukulele in the Classroom’. The obtained results indicated that the compulsory group music training seemed positively associated with sympathy and prosocial skills among 8- and 9-year-olds, however, only when children showed poor social skills at the beginning of the study (Schellenberg et al., 2015). Even though the ecological validity of the music program was high in this study, the program did have a pedagogical approach of emphasizing particularly helpful behavior, perhaps explaining the improvement in social skills. Moreover, potential effects of non-musical extra-curricular activities on social functioning were not controlled for in this study. Simply participating in any group activity may explain the observed results of Schellenberg et al. (2015) as well, making it impossible to pinpoint the particular value of synchronizing behavior combined with musical elements in the musical program.
Goldstein & Winner (2012) and Schellenberg (2004) did implement other activities in their studies as a control group, particularly drama lessons, and concluded that those children receiving one year acting lessons exhibited substantial pre- to posttest improvements in adaptive social behavior (Schellenberg, 2004) as well as empathy scores and theory of mind acuity (Goldstein & Winner, 2012), in comparison to subjects in the music groups. However, Rabinowitch et al. (2012) found contrasting results, since emotional empathy measures only significantly increased in a musical group and not in the control group which included drama activities. Nonetheless, since the control group of Rabinowitch et al. (2012) also implemented other activities, such as play, it is difficult to directly compare it with other findings. In addition, both groups were instructed by the same person in Rabinowitch's et al. (2012) study, namely the first author of the article, who was aware of the hypothesis. Thus, the results may also be explained by experimenter effects.
A general remark towards these intervention studies is that they do not describe the different elements of the musical intervention specifically. This makes it difficult to associate certain results of these studies with specific elements of the musical interaction (e.g. synchronization). In addition, unfortunately, none of the discussed studies compared active music participation with other activities involving interpersonal synchrony, making it difficult to disentangle the additive value of musical elements during synchronous movement.
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5.4 Passive music listening without synchronous movement
Only a small amount of studies was found in this category, regarding both children and adult studies. As discussed in the previous section, Gerry et al., (2012) compared active music classes to passive music classes, where social functioning of 6 months old infants improved relatively more after an active music intervention, suggesting that solely listening to music without actual behavioral synchrony, exhibits significantly less influence on the social development of an infant, although this study suffers from methodological weaknesses. Nevertheless, Boer & Abubakar (2014) revealed that music listening in families and peer groups contributes to family and peer cohesion, respectively, although this could also be attributed to mere group activity and not specifically group music listening.
Studies examining adult behavior suggested as well that experiencing music as an audience member (classical, jazz or opera concert) is associated with a greater likelihood of exhibiting certain pro-social behaviors, such as voting, volunteering and community involvement, even after controlling for potential confounding variables as age, income, education and occupational status (Polzella & Forbis, 2014). However, a disadvantage of these two studies is that there is no control of behavioral movement during the attendance of a concert or music listening session at home. In addition, findings of Polzella & Forbis (2014) can possibly also be explained by the psychological mechanism of being part of an audience (Hackman & Katz, 2010).
Interestingly, two studies were found which investigated the influence of music listening on anti-dark-skin prejudice (Clarke, DeNora, & Vuoskoski, 2015; Neto, da Conceicao Pinto, & Mullet, 2016). Neto, da Conceicao Pinto, & Mullet (2016) exposed sixth-grade pupils in Lisbon, Portugal, to a 6-month musical program at school, which included listening to both Portuguese as well as Cape Verdean songs. A control group followed the same music program that involved Portuguese songs only. Subsequently, those in the experimental group showed a reduction in anti-dark-skin prejudice, either implicit or explicit, whereas no reduction was observed in the control group. However, since the musical program included an analysis of the songs listened to as well, the reduction in prejudice could also be attributed to the fact that the group of children was just more involved with the particular culture.
However, comparable evidence was observed in adults, even in the most passive circumstances (solitary headphone listening in a laboratory setting), where implicit attitudes towards cultural others were positively influenced after listening to music originating from that particular culture. Specifically, people with higher dispositional empathy showed more positive associations with images of people from the different cultural groups (Clarke et al., 2015).
At last, as stated in section 4.3, listening to music with a positive valence promotes cooperative behavior (Kniffin et al., 2016), as well as preferred ‘chill-inducing’ music listening (Fukui & Toyoshima, 2014). These findings confirm predictions made by the arousal-mood
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hypothesis and suggest that behavioral synchrony is not essential in the influence of music on prosocial behavior. In sum, group music listening seems to contribute to prosocial behavior as well as social cohesion, although more research is necessary to clarify this issue where participants’ movements are taken into consideration as well as the possible confounding factor of simply participating in a group activity. Moreover, it is suggested that solitary music listening influences implicit attitudes towards cultural others, additionally, it may affect our emotional state, consequently, influencing our behavior.
5.5 Summary
Interpersonal synchrony, in silence or accompanied by a metronome, seems to positively influence social attitudes of children. Whether this impact has consequences regarding prosocial behavior was not tested unfortunately. Group dancing is suggested to affect prosocial attitudes as well as behavior, although via different processes, as movement symmetry in reference to the same beat increases prosocial attitudes, whereas prosocial behaviors are enhanced by mere rhythmic equality, where everybody dances to the same beat without performing similar movements. Whether music listening alone has an impact on children is not very clear given the amount of studies into this topic. Not only dancing, also singing seems to promote cooperation in children, as well as the combination joint music making and play. Others suggest that a year of music lessons may also affect social functioning of children, but only for those who begin with poor social skills. Although, other activities as drama lessons may result in even greater outcomes. Even though the effect of interpersonal synchrony on cooperative behavior seems established in adults, some synchronization activities, specifically rowing, show contradicting results indirectly. However, when accompanied by a metronome sound, interpersonal synchrony does seem to support prosocial attitude and behavior, remarkably, resulting in generalized prosociality. In contrast, when dancing to a rich song, even though feelings of closeness are heightened, behavioral outcome is not affected. This outcome is applicable to synchronous drumming as well, where drumming only promotes cooperation if combined with a sacred value. Collective singing, on the other hand, has been shown to influence both adults attitude and behavior. Whilst evidence regarding mere music listening is lacking in children, adults do seem to be positively influenced by particular music listening, indicating that behavioral synchrony is not essential in the influence of music on prosocial behavior.
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6. Discussion
6.1 Main findings: prosocial attitude vs prosocial behavior
Research into the social influences of interpersonal synchrony has gained more attention the last years. The current review has tried to disentangle the potential role of musical elements in the social effects of behavioral synchrony, whilst comparing children and adult studies. For clarity, distinctions have been made between influences on prosocial attitudes and effects on prosocial behavior.
The observed results suggest that both children’s and adults’ prosocial attitudes, such as self-similarity and preference, can be influenced by movement symmetry alone, thus, without an external pacesetter, or when accompanied by an auditory metronome. Whether children’s prosocial behavior is influenced by mere movement symmetry as well, is not clear yet however. In adults, mere movement symmetry does seem to be enough to impact cooperative behavior, although no direct evidence has been observed for rowing, a sport extremely demanding in synchronous behavior.
Studies investigating dancing show contradicting results. Both children’s and adults’ social attitudes is suggested to benefit from dancing together, although a combination of movement symmetry and rhythmic equality seems necessary to actually impact children’s prosocial attitude, suggesting that relevant sound support is required to influence children’s attitude towards group-members. Interestingly, rhythmic equality alone (people dancing to the same music without performing identical movements), is suggested to have a positive behavioral influence in children, indicating that movement symmetry is redundant in enhancing prosocial behavior. An increase in adults’ prosocial behavior did not follow after dancing in synch.
Regarding the social behavioral influences of children’s drumming, a combination of play and joint music making seems to be of relevance, whereas ritualization of the drumming activity is suggested to be necessary to positively influence social behavior of adults. Adults’ attitudes, on the other hand, do seem to be impacted from mere synchronous drumming.
Taken together, these findings indicate that children and adults respond differently upon interpersonal synchrony accompanied by musical elements. In addition, it seems that prosocial attitudes and prosocial behavior engage different processes and that they are not directly related to each other, since attitudes can be influenced without impacting consequent behavior. This is not in accordance with statements made in paragraph 3.3, where it is argued that self-similarity and empathy are positively associated with prosocial behavior (Fukui & Toyoshima, 2014; Mahajan & Wynn, 2012; Rabinowitch et al., 2012; van Lissa et al., 2014).
Whether longitudinal music programs have social influences is difficult to say due to methodological weaknesses often found in the studies discussed, such as blindness of the
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experimenter, the design and pedagogical approach of the music program, the absence of a control-group participating in another group activity, and the indistinctness of the content of these programs.
A more general remark towards the other manipulation studies is that prosocial attitudes, such as empathy, and prosocial behavior are generally not assessed before the manipulation phase, even though there are individual differences in dispositional empathy (Clarke et al., 2015) and prosocial behavior. In other words, participants who showed more cooperative behavior or prosocial attitudes after the (a)synchrony manipulation might have been more empathic and cooperative to begin with. This is something for future research to take in mind.
6.2 Additional value of musical elements?
In chapter 4 multiple hypotheses were proposed as to why music may serve an additional value in the process of interpersonal synchrony and its prosocial consequences. However, from the discussed studies in this review it has become clear that synchrony accuracy (see paragraph 4.1) is not affecting the prosocial outcome. Therefore, even though musical elements may increase synchrony accuracy of the group members, this will probably not affect the prosocial consequences of movement symmetry alone.
Evidence for the arousal-mood hypothesis, that is the capacity of music to affect emotional states which in turn may have prosocial consequences (see paragraph 4.3), has been found, but only during passive music listening without physical movement. This gives no direct answer regarding mood and arousal effects during actual interpersonal synchrony activities. According to Koelsch (2013) synchronous behavior alone may already lead to pleasure. However, when examining the summarized behavioral studies more closely, it seems that no difference in mood is observed after moving either synchronous or asynchronous (Reddish et al., 2014; Tarr, Launay, & Dunbar, 2015; Wiltermuth & Heath, 2009), indicating that the effect of mere synchronous behavior, relative to asynchronous movement, cannot be explained by mood and arousal levels.
Unfortunately, a study comparing activities with and without musical elements, whilst both involving interpersonal synchrony to some extent (Kirschner & Tomasello, 2010, see section 5.3.1), did not take mood measurements into account, making it impossible to conclude whether an emotional response through music played a significant role during interpersonal synchrony. It is recommended to replicate the study of Kirschner & Tomasello (2010) whilst measuring mood and arousal levels, additionally, other methodological weaknesses need to be taken into account such as blinding the experimenter for the hypothesis.
In addition, due to the varying results of the studies, with and without music, it is hard to pinpoint whether there is an additive value of music among children and adults social functioning. Possibly, this indicates that different situations and groups, benefit differently from musical
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environments. For instance, where children’s social behavior actually benefits from group dancing to musical songs, adults experience no additive value of passive music listening during interpersonal synchrony. A recommendation for future studies is to compare several activities involving movement synchronization that differ in musical elements, amongst different age groups. This may shed more light on the particular issue and the role of music, as well as the influence of mere movement symmetry on social functioning.
Interestingly, a very recent article from Rennung & Göritz (2016) published the results of a meta-analysis regarding the social influence of interpersonal synchrony. Here, sixty studies were included of which 31 implemented musical elements (e.g. metronome beats, musical songs, participants producing music via drumming or singing). The authors examined whether interpersonal synchrony was more effective in eliciting prosocial effects when accompanied by musical elements amongst others. According to their results no evidence was found for a moderating effect of music for both attitudinal and behavioral prosociality (Rennung & Göritz, 2016), implying no additive value of music in the effect of interpersonal synchrony. Nonetheless, in their meta-analysis, adult and children studies were taken together while they did not control for an age variable. This is a weakness of the study given the contrasting results among the different age groups observed in the current review.
Nevertheless, Rennung & Göritz (2016) did find that interpersonal synchrony in general significantly increased both prosocial attitudes and behaviors, with a medium effect size. However, the observed effect decreased to insignificance, in case of prosocial behavior results, when the experimenter was blinded for the hypothesis, indicating an important role of the leading experimenter in the effect of interpersonal synchrony. As mentioned in chapter 5, some studies included in this review did not blind the leading experimenter for the hypothesis also, making the obtained findings unreliable, given the significant role of the experimenter indicated by Rennung & Göritz (2016).
Ultimately, even though the exact value of music in interpersonal synchrony seems hard to define, perhaps the additional value of music is that it simply increases the chance of behavioral synchrony to occur in our day-to-day routines. When music is present, humans have a natural and almost automatic tendency to respond with their body to the beat they sense (see paragraph 2.3). No other modality has this capacity of fostering interpersonal synchrony so strongly as the auditory system, making music a valuable factor in itself.
6.3 Underlying mechanism regarding behavioral synchrony and prosocial consequences
Even though an extensive amount of behavioral studies have been conducted examining the social influence of synchronous movement, the underlying mechanism as to why interpersonal synchrony occasionally results in prosocial attitudes and behavior remains unclear, although
