THERE WAS A TIME when soldiers went into battle in columns and rows. They would line up and march in orderly formation toward the enemy, armed with spears, bayonets or some other weapon of close combat. The enemy would do the same thing. One of these well-oiled formations would kill more soldiers than the otherand win the battle.

Advances in firearms long ago made the marching formation obsolete. It just does not work with machine guns and guerilla warfare. Yet armies all over the world still train for this archaic kind of warfare. Indeed, militaries continue to place a high value on precision and synchrony that will never be used on a battlefield.

Why is that? Why do high schools have marching bands? Why do churches have choirs? And perhaps most perplexing of all, why do we have synchronized swimming? What is it about moving and chanting and singing in unison that appears to have universal appeal?

Bonding and Effervescence
Anthropologists and cultural historians have offered up a variety of theories about synchrony over the years, mostly having to do with group coherence. One theory, for example, holds that various communities benefit from the actual physical synchronyor muscular bondingwhich builds group cohesiveness. Another idea is that synchronous activities lead to collective effervescencepositive emotions that break down the boundaries between self and group.

But neither of these theories has been proved, and what is more, neither is complete. Muscular bonding may explain the coherence of the 14th Infantry Regiment, but those guys do not seem very effervescentnot in the way that, say, carnival revelers are. And gross motor coordination does not explain the almost motionless chanting of Tibetan monks. Psychologists are looking for a unifying theory for the appeal of synchrony.

One idea, put forth by Stanford University psychologist Chip Heath and graduate student Scott S. Wiltermuth, is that all synchronymovement and sound, and both togetheris an ancient ritual that evolved for the economic benefit of the group. The primary goal of rhythmic dancing, marching and chanting is to solve the problem of the freeloaderthe community member who hurts the collective good by taking but not contributing. Muscular bonding and collective joy are mere by-products of this more fundamental economic ritual.

Heath and Wiltermuth ran a series of experiments to test this idea. In the simplest version, the researchers took groups of Stanford students on walks around campus; some walked in stepmarching, basicallywhereas others just strolled the way people usually do. Later, after the subjects thought the experiment was over, the psychologists gave them all the Weak Link test, in which each volunteer chooses to act either self-interestedly or cooperatively, depending on what he or she anticipates others will do. The test measures the expectation that others will value the group over themselves.

The marchers acted more cooperatively than the strollers did. They also said that they felt more connected than the strollers did. Notably, they did not report feeling any happier, suggesting that positive emotions were not necessary for achieving the boost in group cohesiveness.

The psychologists wanted to do a more fine-grained test of their idea. It is well known that a sense of common identity and shared fate strengthens group cohesiveness, but the researchers wanted to see if synchrony contributes above and beyond this feeling. They did a rather elaborate test to find out. They had students perform tasksmoving plastic cupsthat required differing degrees of coordination with others. While doing this, the subjects listened to O Canada through headphones. Remember that these participants were from Stanford (and thus typically U.S. citizens), so the Canadian national anthem presumably had no emotional resonance for them; it was merely a synchronous act.

All the students had copies of the lyrics. Some sang the anthem and moved the cups in rhythm, whereas others just sang in unison or read the lyrics silently. Still others sang nd moved to different temposkind of like a really bad dancer moving at odds with the music.

Then the researchers gave them the same Weak Link test, only this time there was real money involved. As before, those who had experienced synchrony were more economically cooperative than those who had not. The bad dancers were bad citizens, but the physical movement otherwise made no difference; choral singers were selfless with or without the swaying, suggesting that muscular bonding is (like joy) unnecessary to get the desired group coherence. The swaying might have been enjoyable, but the group singing was sufficient.

Tokens of Esteem
The Stanford team did this O Canada experiment again with a different but similar test called the public goods game. Using tokens, participants choose whether to contribute to a public kitty or to their own private savings account. Self-interest has a higher payoff in the game, although the group benefits more if everyone acts unselfishly. The researchers got the same results as before, but the interesting finding was that, over the games several rounds, the choral singers increased their contribution to the group, keeping less money for themselves. They gave much more to the community fund in the last round than they did in the first, suggesting that the synchrony has persistent and growing effects.

The choral singers also said they felt as if they were more part of the team. They felt they had more in common with the others, and they trusted them somewhat more. Interestingly, as reported in the January issue of the journal Psychological Science, they also made more money in the end because they shared in the group bounty.

Synchrony rituals are powerfulso much so that they may have endowed certain groups with a competitive advantage over the eons, perhaps even causing some cultures to flourish while others perished. It is no wonder, then, that such potent impulses remain entrenched in todays churches and armiesand, yes, could even explain synchronized swimming.

Note: This article was originally printed with the title, "All Together Now".