Original ArticleSilent disco: dancing in synchrony leads to elevated pain thresholds and social closeness
Introduction
Around the world people sing, make music and dance—activities which are often conducted in a group setting, accompanied by strong emotions, and can be broadly defined as “musicking” (Small, 1998). The evolutionary origin of dance, which involves synchrony of movement to others and to music, remains unclear. One prominent theory is that this behavior might have played an important role in increasing interpersonal cooperation and feelings of social closeness, thereby helping to establish and maintain group cohesion (Freeman, 2000, Kirschner and Tomasello, 2010, Reddish et al., 2013, Tarr et al., 2014).
Like most anthropoid primates, humans live in bonded social groups (Dunbar & Shultz, 2010). Bonded social groups allow their members to mount a coordinated (passive and active) defense against predators or conspecific raiders (Lehmann, Lee, & Dunbar, 2014), and provide direct fitness benefits by buffering individuals against the stresses of social life (Wittig et al., 2008) and enhancing infant survival (monkeys: Silk et al., 2003, Silk, 2007; humans: Spence, 1954, Oesch and Dunbar, 2015). Allogrooming is a conventional mechanism for social bonding in primates, including humans, but is very expensive in terms of time, and therefore imposes a limit on the size of networks or groups that can be effectively bonded (Dunbar, Korstjens, & Lehmann, 2009). It would have been advantageous for humans to develop additional behaviors that allow bonding between multiple individuals simultaneously so as to allow us to increase the size of our social networks and communities (Dunbar, 2012a). Musicking may facilitate efficient large-scale bonding: when moving together to music, individuals can establish social closeness with the whole of the group involved (Dunbar, 2012b, Kirschner and Tomasello, 2010, Wiltermuth and Heath, 2009). To date, empirical evidence that dance can lead to social bonding has focused on the role of our innate capacity to perceive and synchronize to a rhythmic pattern (Patel, Iversen, Chen, & Repp, 2005), particularly beats embedded in music (Demos, Chaffin, Begosh, Daniels, & Marsh, 2012) or those produced by another human (Kirschner & Tomasello, 2009).
Synchronization is a pervasive behavior in many animals, playing a part in female identification of conspecific males (e.g., fireflies: Moiseff & Copeland, 2010), pair formation displays (e.g., western grebes: Nuechterlein & Storer, 1982), and courtship (e.g., fiddler crabs: Backwell, Jennions, & Passmore, 1998). The capacity to synchronize specifically to a musical beat is not uniquely human, and we share this aspect of music cognition with certain other species (Patel et al., 2009, Patel et al., 2008). Although there is some evidence that chimpanzees are capable of learning to spontaneously synchronize to an auditory beat (Hattori, Tomonaga, & Matsuzawa, 2013), our proclivity to produce organized rhythmic sound (music) and our mutual entrainment as occurs when we dance, remains characteristically human (Fitch, 2012).
Like mimicry (e.g., Chartrand & Lakin, 2013), synchrony has received much attention in accounts of human social-cognitive functioning (Macrae, Duffy, Miles, & Lawrence, 2008). When people perform the same movements at the same time (i.e., synchronize), there is a co-activation of action and perception networks which is believed to blur a sense of ‘other’ and ‘self’ (Overy & Molnar-Szakacs, 2009), leading to a social bond between co-performers (e.g., Decety & Sommerville, 2003). This mechanism is argued to explain why small movement synchrony (e.g., finger tapping) increases participants’ feelings of affiliation towards a tapping partner, as measured by self-reported similarity in personality (Valdesolo & Desteno, 2011) and how much participants like their co-actor (Hove and Risen, 2009, Valdesolo and Desteno, 2011). This effect is evident with real and virtual partners (Launay, Dean, & Bailes, 2014), and also manifests in prosocial behaviors such as willingness to help a partner with whom someone has synchronized (Kirschner and Tomasello, 2010, Kokal et al., 2011, Valdesolo and Desteno, 2011), and positive behavior in economic games (Launay et al., 2013, Wiltermuth and Heath, 2009).
Synchronization has been shown to facilitate entitativity – the feeling of being ‘on the same team’ (e.g., Lakens, 2010) – which can then lead to enhanced cooperation and prosociality, possibly due to a sense of collective fate (Wiltermuth & Heath, 2009). Synchronized action has also been described as increasing action understanding of others via “motor resonance” (Macrae et al., 2008), whereby self-other attentional coupling facilitates social cognition (Blakemore & Decety, 2001) by facilitating observational learning (Wilson & Knoblich, 2005) and enhancing person-related processing (Knoblich & Sebanz, 2006). This seemingly primes co-actors to establish trust and so coordinate better, as demonstrated by the fact that synchronized movement can predict success in a later joint activity that demands collaboration (Valdesolo, Ouyang, & DeSteno, 2010). Furthermore, people preferentially direct compassion and altruism toward similar others (e.g., Strürmer, Snyder, Kropp, & Siem, 2006), and synchrony (which enhances perception of similarity between co-actors) may be a means of creating a unified in-group. As a result of these various socio-cognitive effects, it is hypothesized that the prosocial effects encouraged during synchrony would be evolutionarily advantageous in other domains which require smooth coordination such as hunting, gathering, building shelters together and mutual defence against predators or conspecific raiders.
Although action–perception matching is often cited as the main mechanism underpinning the social bonding effects of synchronization, it has also been suggested that social activities such as musicking may trigger the Endogenous Opioid System (EOS; Dunbar et al., 2012b, Tarr et al., 2014), which is known to be involved in social bonding in non-human primates (e.g., Ragen, Maninger, Mendoza, Jarcho, & Bales, 2013). The EOS consists of opioid-producing nuclei in the hypothalamus and opioid receptors that are distributed throughout the central nervous system and is generally studied in humans for its analgesic and reward-inducing effects (Bodnar, 2008). The Brain Opioid Theory of Social Attachment (BOTSA) highlights the fact that social attachment involves elevated levels of opioids in the brain (Machin and Dunbar, 2011, Nummenmaa et al., 2015), and that the positive effects of social interaction are similar to those induced by opiates (Machin & Dunbar, 2011). Activation of the EOS is associated with feelings of euphoria (Bodnar, 2008), interpersonal warmth, well-being, and bliss (Depue & Morrone-Strupinsky, 2005), reward (Olmstead & Franklin, 1997), social motivation (Chelnokova et al., 2014), and pleasure and pain perception (Leknes & Tracey, 2008). Given the role of the EOS in social bonding in mammals generally (Broad, Curley, & Keverne, 2006), it is argued that human behaviors which activate the EOS lead to perception of closer social bonds between co-actors (e.g., Dunbar, 2004, Dunbar, 2012b). According to BOTSA, the EOS may have been ‘co-opted’ from its more general role in pain relief and positivity to reinforce social behaviors (Eisenberger, 2015, Macdonald and Leary, 2005, Panksepp, 1999).
Group activities which increase pain threshold (a recognized proxy measure of endorphin levels; Mueller et al., 2010) include laughter (Dezecache and Dunbar, 2012, Dunbar et al., 2012a), group exercise (Sullivan, Rickers, Gagnon, Gammage, & Peters, 2011) and synchronized sport (Cohen et al., 2010, Sullivan and Rickers, 2013, Sullivan et al., 2014). Rowing in synchrony elevates pain threshold compared to rowing alone (Cohen et al., 2010) or when unsynchronized (Sullivan et al., 2014), irrespective of whether the rowers are strangers or acquaintances (Sullivan & Rickers, 2013). Furthermore, active participation in group music-based activities is similarly associated with increased pain threshold (Dunbar, Kaskatis, et al., 2012). Although these studies did not measure social closeness directly, they postulate that EOS activation (specifically elevated endorphin levels) as indexed by pain threshold may play a role in the bonding that is associated with these various social activities.
The current experiment investigates changes in social bonding and pain thresholds associated with synchronized dance in groups of strangers. Existing research on the link between synchrony and social bonding has predominantly focused on synchronization of small movements such as rocking in a chair (Demos et al., 2012), walking in step (Wiltermuth & Heath, 2009), finger tapping (Launay et al., 2013), or the performance of simple arm and leg movements in time with others or a metronome (Reddish et al., 2013). These studies demonstrate that synchronization of simple movements by pairs of people or small groups leads to increased social bonding, as measured by both self-report and behavioral measures. Nevertheless, dance is arguably more than scaled up finger tapping. Few studies have investigated the effect in groups larger than two with music, or with movement conditions representative of dance (e.g., instead using conditions of walking, singing, waving cups: Kirschner and Tomasello, 2010, Wiltermuth and Heath, 2009).
In the present study, groups of four individuals performed dance movements to popular music. We used a ‘silent disco’ paradigm in which participants dancing in a group heard music through individual headphones; thus, any social bonding that occurs can be attributed to behavioral synchrony of dance actions. The silent disco technology allowed us to compare the synchronous condition to two non-synchronous conditions: partial synchrony (counterbalanced movements, same music) and asynchrony (unique movements and different music). Previous studies report a group synchrony effect in comparison to no-movement conditions (e.g., Wiltermuth & Heath, 2009) or sequential (cannon) movements (e.g., Reddish et al., 2014, Reddish et al., 2013) and it is unclear whether the positive effects associated with synchrony are due to synchronization itself, or negative effects that arise in certain non-synchronous conditions. In addition to self-report questions and a behavioral measure of social closeness (the weak-link coordination game adapted from Wiltermuth and Heath (2009)), the present study includes pain threshold as a proxy measure of EOS activation.
Section snippets
Participants
After exclusions, a final sample of 94 participants (74 females; x̅ age = 24.29, SD = 5.29 years) was recruited in Oxford. To avoid biases in pain threshold measurements, the sample excluded pregnant, lactating or diabetic individuals (McKinney, Tims, Kumar, & Kumar, 1997), and participants who had smoked or drunk alcohol within the two hours prior to the experiment.
General study design
Test groups consisting of four strangers were randomly assigned to a movement condition (synchrony, partial synchrony or asynchrony;
Baseline differences
The movement conditions differed with respect to three baseline measures: conscientiousness (F(2) = 3.232, n = 94, p = 0.044), extraversion (F(2) = 3.640, n = 94, p = 0.041) and self-reported confidence in ability to remember the dance moves (F(2) = 4.658, n = 94, p = 0.012; ESM1, Table S2, available on the journal's Web site at www.ehbonline.org). These three variables were included as covariates in all subsequent analyses, although omitting them did not change the overall results. There were no significant
Discussion
This study investigated whether synchrony influences social bonding and pain threshold during a group dancing activity; synchronizing full-body dance movements increased strangers’ self-reported feelings of social closeness to one another and elevated pain thresholds. These effects arose when participants synchronized with each other and the music, rather than merely with the music. Moving in asynchrony or a partially synchronized manner caused no change or a decrease in pain threshold
Conclusions
The ability to synchronize to rhythmic beats and/or with conspecifics exists in a variety of species, and its occurrence and role in human musicking is of ongoing scientific interest. Although the use of individual headphones was necessary to create the non-synchronized conditions, resulting in a fairly contrived dance experience, this study extends previous research on the link between synchrony and social bonding by having participants perform full-bodied movements to popular music in a group
Supplementary Materials
The following are the supplementary data related to this article.
Acknowledgments
This study was funded by an ERC Advanced Investigator grant to the senior author (295663). We thank the many research assistants who helped throughout data collection, including colleagues at our Research Lab, and Matei Cirstea for modeling the dance movements in the training videos.
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