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The Eleventh Commandment: Punish Free Riders

Religion and the evolutionary origin of cooperation

Ronald Bailey
November 30, 2010

Two of the deep puzzles in human evolution are religion and cooperation between genetically unrelated strangers. In recent years, many researchers have come to believe the two phenomena are intimately linked. If people believe they are being watched and judged by an omnipresent supernatural entity, they may be more willing to perform emotionally binding and costly rituals to signal commitment to a group. The same sense of being watched may also encourage people to be helpful to others—even when there is no obvious reproductive payoff. In other words: Science suggests that God—and His followers—hate free riders.

A 2007 study by University of British Columbia psychologists Azim Shariff and Ara Norenzayan found that players in an anonymous economic game were more generous if they were primed with religious concepts before beginning play. In the case, the subjects participated in the dictator game in which they get to anonymously divvy up $10 between themselves and an unknown individual. The researchers assigned players into three groups. One group was primed with religious concepts by having them unscramble 10 five-word sentences, dropping an extraneous word from each to create a grammatical four-word sentence. For example, “dessert divine was fork the’’ would become ‘‘the dessert was divine.” The religious words were spirit, divine, God, sacred, and prophet. A second group was primed with words connoting secular moral institutions, e.g., civic, jury, court, police, and contract. The third group unscrambled sentences containing neutral words. So what did they find?

Earlier studies using the dictator game consistently found that subjects in general behaved selfishly by taking most of the money for themselves. In this case, players in the neutral game offered an average of $2.56 to other players. However, players who had been primed with religious concepts offered an average of $4.56. Interestingly, players primed with secular moral concepts offered $4.44, nearly as much as players exposed to religious primes. Self-reported belief in God was not a good predictor of generosity in the neutral prime version of the game; it seems believers needed reminders to be more generous.

But how do the invisible omnipresent gods encourage generosity to strangers? Of course, the gods can reward believers for good behavior, but they also punish them for bad behavior. It is how this aspect of religious belief affects cooperation that a team of researchers led by University of London psychologist Ryan McKay attempt to probe in a study released last week, “Wrath of God: Religious primes and punishment.”

One of the chief fears of people who want to cooperate is that they will be chumps who are taken advantage of by free riders. Earlier research using public goods economic games found that cooperation was considerably enhanced if players had an opportunity to punish free riders. In these games, players can invest in a common pool which then grows and is divvied up among all the players. Free riders, however, can make more money by refusing to invest and yet get a share of the growing pool. Research shows that cooperation breaks down completely when such free riders cannot be punished by other players. But when other players can pay to reduce the holdings of free riders, they begin to play fairly and cooperation dramatically increases.

In the new study, McKay and his colleagues sought to find out if religious priming promotes costly punishment of unfair behavior. In this experiment, one player could choose between splitting a pot of money evenly between herself and a second player or she could choose another option in which the split was about nine to one. If the second player believed the choice was unfair, she could punish the first player by spending a portion of her allocation to reduce the take of the first player at a rate of three to one, e.g., if she spent 50, the first player would lose 150. The players were subliminally primed by words flashing on a computer screen. Divided into four groups, one group was exposed to religious words, another to punishment words, the third to punishment and religious words, and the fourth to neutral words. Afterwards, players were asked about their religious beliefs and if they had donated to a religious organization in the past year.

The results? “Our study reveals that for those who financially support religious institutions, subliminal religious messages strongly increase the costly punishment of unfair behavior, even when such punishment is to their individual material disadvantage,” says McKay in a press release describing the research. Subliminal religious priming did not have a significant effect on other players. 

So why does religious priming induce committed believers to punish unfair behavior? The researchers suggest two possibilities. The first is that religious primes trigger the idea that one is being watched by the gods. “In this case primed participants punish unfair behaviors because they sense that not doing so will damage their standing in the eyes of a supernatural agent,” they speculate. The second hypothesis is that religious primes “activate cultural norms pertaining to fairness and its enforcement and occasion behavior consistent with those norms.” McKay and his colleagues acknowledge that religious primes might actually invoke both mechanisms. In either case, while the gods may punish uncooperative sinners, their work is considerably enhanced if believers go out of their way to punish sinners too.

These studies do bolster the idea that ancestral belief in supernatural entities enhanced group cooperation, enabling believers to out-compete other groups. As Shariff and Norenzayan observe, “If the cultural spread of supernatural moralizing agents expanded the circle of cooperation to unrelated strangers, it may well have allowed small groups to grow into large-scale societies, from the early towns of Jericho and Ur to the metropolises of today.”

Ronald Bailey is Reason's science correspondent. His book Liberation Biology: The Scientific and Moral Case for the Biotech Revolution is now available from Prometheus Books. This column first appeared at

Ronald Bailey is Science Correspondent

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