A new study examined the link between support for a religion and a willingness to inflict punishment.
Ernst Fehr at the University of Zurich in Switzerland and his team enrolled 304 people sorted into pairs. They played 20 rounds of a game in which the first player was shown a monetary reward and had to choose one of two ways to split it with their partner: they could either share it equally or take a greater share for themselves.
The second player then had the option of punishing the first one by deducting from their reward - but punishing meant the punisher lost a reward unit for each three units they deducted from their partner.
Before deciding on the punishment, the second player was subliminally shown a group of words. These either related to religion - like "divine", "holy", "pious" and "religious" - to secular punishment, or were neutral words like "tractor".
After the game, all players were asked if they had donated money to a religious organisation in the previous year. The team found that those who had donated - about 15 per cent of participants - exacted the most severe punishments, but only after they had been shown the subliminal religious cues.
"We think that the cues give them a reminder they are being watched. To please the supernatural agent they worship, they exact higher punishments. The other possibility is that the cued words awakened the concepts of appropriate punishment in their minds," New Scientist quoted psychologist Ryan McKay of Royal Holloway University of London, as saying.
McKay pointed out that being religious can be costly in various ways: donating money, suffering painful rites and avoiding pleasures, for example. So the team wondered how religion survived, despite these apparent costs.
"The answer may be that these sacrifices enable the group to secure more cooperation. The punishing may be unpleasant but it's in the service of the greater good for that particular group or religion, enabling them to thrive and spread the word," he said.
The study appears in Proceedings of the Royal Society B.