If you've ever watched the TV show Survivor, you've no doubt noticed how crucial alliances are and how they constantly change and shift as players jockey for position and try to keep themselves from getting voted out of the game. Part of the reason an alliance of more than two people is so hard to keep together is that there's always a hierarchy of allegiance; loyalty, support, and protection do not apply equally among all. This is usually the argument one alliance uses to lure over a player from the bottom of another, bigger alliance: Being fourth from the top in our alliance, they say, is better than being fifth from the top in theirs. It's an argument that works with varying success.
So I was interested to read about a new theory called the "Alliance Hypothesis for Human Friendship," based on a study by Peter DeScioli and Robert Kurzban, psychologists at the University of Pennsylvania. The psychologists say that how you rank your best friends is closely related to how you think these friends rank you.
As Kurzban notes:

Friendships are about alliances. We live in a world where conflict can arise and allies must be in position beforehand. This new hypothesis takes into account how we value those alliances. In a way, one of the main predictors of friendship is the value of the alliance. The value of an ally, or friend, drops with every additional alliance they must make, so the best alliance is one in which your ally ranks you above everyone else as well.

Traditionally, friends have been thought of as "exchange partners" based on the "theory of reciprocal altruism." But research has shown that we don't regularly keep track of the benefits we give and receive in our close friendships, and we help close friends even when the likelihood of them repaying us is slim. The "alliance" theory of friendship is more optimistic since “it’s not what you can do for me, it’s how much you like me," says Kurzban. "In this manner even the weakest nations, for example, or the least popular kid at the party with nary an alliance in the room is set up to be paired with someone looking for a friend.”
Assuming he's right, can we use this to our advantage? Yup, the psychologists say, by 1) ranking our friends, 2) ranking them according to our position in their rankings (preferring friends who rank us higher—our more reliable allies), and 3) hiding our friend-ranking. —Heather Wax

Those who set an example of cooperative, collective behavior make groups they’re in more successful, according to a recent study. “Groups and organizations face a fundamental problem: They need cooperation but their members have incentives to free ride,” J. Mark Weber, a professor of organizational behavior at the University of Toronto, and J. Keith Murnighan, a professor of management and organization at Northwestern University, write in the study, published in the Journal of Personality and Social Psychology. Weber and Murnighan looked at data from experiments in which participants could either keep small amounts of money or contribute them to the group. The “consistent contributors”—those who offered up their money regardless of what others did—set a tone of cooperation that made their groups more efficient and productive. In the end, everyone in the consistent contributors’ groups came out ahead, challenging the common wisdom that consistent contributors were suckers who always finished last. — Kimberly Roots

A new study out of Stanford University suggests that when people participate in synchronized activities—like the singing and chanting involved in many religious rituals—they become more likely to cooperate with one another. In one experiment, psychologists Scott Wiltermuth and Chip Heath had two groups of people walk around campus, one group walking normally and the other in-step. In another experiment, they had two groups listen to music on headphones and move cups back and forth in time to the beat. The members of one group all listened to the same music (so their movements were synchronous), while members of the other group listened to music with different tempos. After both experiments, members of the synchronized groups had a stronger sense that they were part of the same team, and they were more cooperative when they played economic games set up by the researchers—even making personal sacrifices, such as giving up their own money, to benefit the group. According to the researchers, who publish their results in the journal Psychological Science, "synchrony rituals may have therefore endowed some cultural groups with an advantage in societal evolution, leading some groups to survive where others have failed." —Heather Wax

Costly punishment—in which one person punishes another at a cost to himself—rarely pays off, according to a new study by Harvard University mathematician and biologist Martin Nowak and his colleagues Hisashi Ohtsuki and Yoh Iwasa that appears in last week's edition of the journal Nature. In fact, Nowak says, "efficient cooperation cannot be based on punishment. This is a very positive result."
To study cooperation and punishment, the scientists created a computer simulation of a population in which each interaction leads to either a good or bad reputation; cooperation leads to a good reputation, while not cooperating leads to a bad one. Players could then choose whether to cooperate, punish, or opt out of interactions with another player—based on their observations of the other person and information about the person's past decisions with other players. "Our behavior toward other people depends not only on what they have done to us but also on what they have done to others. Indirect reciprocity works through reputation," the researchers write.
When asked if they want to donate money to another person, for example, the "experiment shows that people base their decisions on what the recipient has done before. Generous people are more likely to receive donations," writes Nowak in an essay that appeared in an earlier edition of Nature. Because we spend most of our lives in a relatively small population in which we interact with the same people over and over again, we continually monitor and interpret how others act toward us and others. "When deciding how to act, we take into account—often subconsciously—the possible consequences for our own reputation," Nowak says. "Moreover, our own observations are often not enough; we want to learn from the experiences of others."
Punishment, the researchers found, is only a successful strategy when our assessment of other people's reputations—and what others say about them—is reliable; in real life, however, perception and gossip can often lead to errors. In most cases, then, a population does better by not using punishment; instead, the best strategy is to withhold help from someone you think has a poor reputation or has made unfavorable decisions in the past. —Heather Wax

People who believe in God tend to be more honest, helpful, and generous than those who aren't believers—but only when they think such acts will enhance their personal reputation or when religious thoughts are freshly activated (even subconsciously) in their minds, according to a new study published in the journal Science. In other words, religious people are on their best behavior when they think God or others are watching.
To reach this conclusion, University of British Columbia social psychologists Ara Norenzayan and Azim Shariff looked at anthropology, sociology, psychology, and economics research from the last 30 years. They found that across the disciplines, religion and belief in a morally concerned God are shown to foster cooperation and trust, and make people more likely to engage in prosocial behavior (acts that benefit others at a personal cost). "One reason we now have large, cooperative societies may be that some aspects of religion—such as outsourcing costly social policing duties to all-powerful Gods—made societies work more cooperatively in the past," says Shariff. These large, stable societies, the researchers explain, were then able to successfully pass on their cultural beliefs.
But the study also finds that in many cases, those who don't believe in God act as prosocially as religious believers do, and there are certainly nonreligious institutions that involve effective policing and social surveillance. "Some of the most cooperative modern societies are also the most secular," Norenzayan says. "People have found other ways to be cooperative—without God." —Heather Wax

Martin Nowak, a mathematician and biologist at Harvard University and director of its Program for Evolutionary Dynamics, has long studied cooperation among genes, cells, and humans, and recently, he's been working on mathematically modeling the origin of life. Now, he's started another new research project with Sarah Coakley, formerly at the Harvard Divinity School and now at the University of Cambridge. Together, they're studying the way religious people and nonbelievers think about and view cooperation, and early results show, says Coakley, that those who are religious have a stronger belief in cooperation's power. According to their previous research, which also combined evolutionary theory and theology, cooperation is the centerpiece of a winning game plan for life; the math demonstrates that it pays to be generous, forgiving, and hopeful. —Heather Wax

A group of researchers led by Martin Nowak, a professor of biology and mathematics and director of the Program for Evolutionary Dynamics at Harvard University, wrote in to tell us about their new paper, in this week's edition of Nature:

We show that individuals who engage in costly punishment in a cooperation game do not benefit from their behavior. The study found that the use of punitive behavior correlates strongly with reduced individual payoff, and bestows no benefit on the group as a whole.
These results demonstrate that costly punishment is not an effective force for promoting cooperation. The unfortunate tendency of humans to engage in acts of spiteful punishment must have evolved for other reasons such as establishing dominance hierarchy and defending ownership, but not to promote cooperation. In cooperation games, costly punishment is a detrimental and self-destructive behavior.
Our finding has a very positive message: In an extremely competitive setting, the winners are those who resist the temptation to escalate conflicts, while the losers punish and perish.
—Anna Dreber, department of economics, Stockholm School of Economics, Harvard's Program for Evolutionary Dynamics
David Rand, Harvard's Program for Evolutionary Dynamics and department of systems biology
Drew Fudenberg, Harvard's department of economics
Martin Nowak, Harvard's Program for Evolutionary Dynamics, department of mathematics, and department of organismic and evolutionary biology