The fear that a punitive god is watching may have helped drive humanity’s global expansion, a team of international researchers argues in a new paper.

Their research, conducted in communities around the world and summarized in a peer-reviewed paper published by the journal Nature, finds that people who hold such beliefs about god tend to act less selfishly.

When people are inclined to behave impartially toward others – even if that’s because they fear retribution – they are more likely to adopt behaviors that can create and support large-scale cooperative institutions, such as trade and markets.

“They’re playing by the rules towards people they never interact with,” said lead author Benjamin Purzycki, a postdoctoral research fellow at the University of British Columbia’s Centre for Human Evolution, Cognition, and Culture.

That magnanimous behavior, Purzycki and his colleagues argue, may be what helped foster the trust needed for humanity’s growth.

To understand how religious belief affects individual behavior, the researchers set up experiments in eight communities of varying size in Brazil, Fiji, Mauritius, Siberia, Tanzania and Vanuatu.

Nearly 600 people participated, representing a wide range of faiths from Christianity and Hinduism to Buddhism, animism and ancestor worship.

The researchers asked each participant to play a pair of economic games. In each game, participants received 30 coins, two cups and a dice with half of its six sides one color and the other half another color. They were told to mentally pick a cup and roll the dice; then they were instructed, based on the dice color, to put the coin either into the cup they were imagining or the one they weren’t.

In both experiments, one cup was assigned to a distant and anonymous adherent of the participant’s religion. The second cup was either assigned to the participant or to an anonymous local adherent of the same religion.

Participants were told that each cup’s contents at the end of the game would go to whomever it was assigned. After the games, they were also asked a series of questions related to their religious beliefs.

In theory, the game would end with an average of 15 coins evenly split in either cup, because of random chance.

But the experimenters designed the game to make it easy to cheat: because participants chose the cup in their head, they could easily override the rules. And they did.

As might be expected, participants were most likely to cheat in their own favor; they were least likely to cheat in favor of their “distant co-religionists.”

But the higher a participant rated their god as moralistic, knowledgeable and punishing, the fairer they were to the distant stranger of the same faith.

Participants who believed in a moralistic and punishing god were about five times fairer to their distant “co-religionists” than participants who didn’t know whether their god was moralistic, the researchers found.

The effect of fear remained even after they accounted for other variables – for example, belief in divine rewards for good behavior.

Fear, it seems, encourages selflessness, an act that promotes trust.

“When people are more inclined to behave impartially towards others, they are more likely to share beliefs and behaviors that foster the development of larger-scale cooperative institutions, trade, markets and alliances with strangers,” the researchers argue.

Dominic Johnson, a politics professor at the University of Oxford, found the team’s findings particularly compelling.

“Purzycki and colleagues’ study offers the most explicit evidence yet that belief in supernatural punishment has been instrumental in boosting cooperation in human societies,” Johnson wrote in a commentary accompanying their research.

In an audio interview posted to Nature’s website, Johnson described the study as “quite remarkable.”

Purzycki cautioned against drawing too strong a conclusion about the kindness of people of faith, however.

“It’s easy to talk about these results as effectively (suggesting that) religious people are nicer, but I think that’s misleading,” he said.

The findings do suggest cooperation, he said; but that doesn’t necessarily translate to kindness.

“Any sort of terrorist network – they’re really hyper-cooperative,” he said. “We don’t have to like their ends at all, but it’s remarkable how cooperative they are.”

The findings are also limited to individual behavior to their religious peers. People who believe in a punitive god may not be so cooperative with strangers of a different – or no – faith.