For the How to Run a Successful Less Wrong Meetup booklet, I'm looking for information about how to better build a social group and foster a feeling of community. Since this bit is probably of general interest, I'm posting it here.

If you want to make the members of the group like each other more and feel more like a group, synchronized actions may be one of the easiest ways of achieving this goal. Anthropologists have long known the community-building effect of dancing:

As the dancer loses himself in the dance, as he becomes absorbed in the unified community, he reaches a state of elation in which he feels himself filled with an energy of force immensely beyond his ordinary state . . . finding himself in complete and ecstatic harmony with all the fellow-members of his community, experiences a great increase in his feelings of amity and attachment towards them. (Radcliffe-Brown 1933/1948, quoted in Kesebir 2011)

Armies around the world utilize the same effect to foster a feeling of unison through repeated drills:

Words are inadequate to describe the emotion aroused by the prolonged movement in unison that drilling involved. A sense of pervasive well-being is what I recall; more specifically, a strange sense of personal enlargement; a sort of swelling out, becoming bigger than life, thanks to participation in collective ritual. (McNeill 1995, quoted in Kesebir 2011)

Wiltermuth & Heath (2009) summarize some of the research on the topic:

The idea that synchronous movement improves group cohesion has old roots. As historian William H. McNeill suggests, armies, churches, and communities may have all benefited, intentionally or unintentionally, from cultural practices that draw on ‘‘muscular bonding,’’ or physical synchrony, to solidify ties between members (McNeill, 1995). This physical synchrony, which occurs when people move in time with one another, has been argued to produce positive emotions that weaken the boundaries between the self and the group (Ehrenreich, 2006; Hannah, 1977), leading to feelings of collective effervescence that enable groups to remain cohesive (Durkheim, 1915/1965; Haidt, Seder, & Kesebir, in press; Turner, 1969/1995). Andaman Islanders have been said to become ‘‘absorbed in the unified community’’ through dance (Radcliffe-Brown, 1922, p. 252). Similar observations have been made of Carnival revelers (Ehrenreich, 2006), and ravers dancing to beat-heavy music (Olaveson, 2004). Moreover, Haidt et al. (in press) have argued that people must occasionally lose themselves in a larger social organism to achieve the highest levels of individual well-being.

Some recent findings on the topic include:

Wiltermuth & Heath (2009): Synchronous activity in the form of walking around a campus in step causes people to be more likely to make decisions requiring trust and to self-report stronger feelings of trust and connectedness with others. Singing in synchrony, even if the song is an out-group anthem ("O Canada", when the subjects were USA residents), causes more trust and and greater feelings of being on the same team, as well as an increased willingness to cooperate in a public goods game.

Kirschner & Tomasello (2010): "Given that in traditional cultures music making and dancing are often integral parts of important group ceremonies such as initiation rites, weddings or preparations for battle, one hypothesis is that music evolved into a tool that fosters social bonding and group cohesion, ultimately increasing prosocial ingroup behavior and cooperation. Here we provide support for this hypothesis by showing that joint music making among 4-year-old children increases subsequent spontaneous cooperative and helpful behavior, relative to a carefully matched control condition with the same level of social and linguistic interaction but no music."

Valdesolo, Ouyang & DeSteno (2010): Synchronous rocking increases perceptions of similarity and connectedness. The subjects were given the task of holding the opposite ends of a 12 × 14 wooden labyrinth with both hands and guiding a steel ball through it together. The subjects in the synchronous rocking condition performed better than the subjects in the asynchronous rocking condition.

Valdesolo & DeSteno (2011): Subjects who are told to tap the beats they hear in an audio clip, and are paired with a confederate who has been instructed to synchronize his tapping with the participant’s, tend to find like the confederate more and consider him more similar to themselves. The confederate being assigned an unfair task then evokes more feelings of compassion, and the subjects are more likely to help him, even at a cost to themselves.

The implication for meetup groups, as well as any other groups that might want to make their members like each other more, seems clear: spend some time singing and dancing together, possibly in the form of drinking songs if people are too self-conscious to sing while sober. Just make sure that any non-drinkers don't feel excluded. If all else fails, you can always march around the city while chanting "doom doom DOOM DOOM". (If anybody asks, you can say that you're testing a scientific hypothesis about group bonding, and ask if they'd want to join in.)

References

Kesebir, S. (2011) The Superorganism Account of Human Sociality: How and When Human Groups Are Like Beehives (ungated version). Personality and Social Psychology Review.

Kirchner, S. & Tomasello, M. (2010) Joint music making promotes prosocial behavior in 4-year-old children. Evolution and Human Behavior 31, 354–364. 

McNeill, W.H. (1995) Keeping together in time: Dance and drill in human history. Cambridge, MA: Harvard University Press.

Radcliffe-Brown, A. R. (1948) The Andaman Islanders. Glencoe, IL: Free Press.

Valdesolo, P. & DeSteno, D. (2011) Synchrony and the Social Tuning of Compassion. Emotion, vol. 11, no. 2, 262–266. 

Valdesolo, P. & Ouyang, J. & DeSteno, D. (2010) The rhythm of joint action: Synchrony promotes cooperative ability. Journal of Experimental Social Psychology, vol. 46, no. 4, 693–695.

Wiltermuth, S.S. & Heath, C. (2009): Synchrony and Cooperation. Psychological Science, vol. 20, no. 1.