Across history and cultures, religion increases trust within groups but also may increase conflict with other groups, according to an article in a special issue of Science.

"Moralizing gods, emerging over the last few millennia, have enabled large-scale cooperation and sociopolitical conquest even without war," says University of Michigan anthropologist Scott Atran, lead author of the article with Jeremy Ginges of the New School for Social Research.

"Sacred values sustain intractable conflicts like those between the Israelis and the Palestinians that defy rational, business-like negotiation. But they also provide surprising opportunities for resolution."

As evidence for their claim that religion increases trust within groups but may increase conflict with other groups, Atran and Ginges cite a number of studies among different populations. These include cross-cultural surveys and experiments in dozens of societies showing that people who participate most in collective religious rituals are more likely to cooperate with others, and that groups most intensely involved in conflict have the costliest and most physically demanding rituals to galvanize group solidarity in common defense and blind group members to exit strategies. Secular social contracts are more prone to defection, they argue. Their research also indicates that participation in collective religious ritual increases parochial altruism and, in relevant contexts, support for suicide attacks.

They also identify what they call the "backfire effect," which dooms many efforts to broker peace. In many studies that Atran and Ginges carried out with colleagues in Palestine, Israel, Iran, India, Indonesia and Afghanistan, they found that offers of money or other material incentives to compromise sacred values increased anger and opposition to a deal.

"In a 2010 study, Iranians who regarded Iran's right to a nuclear program as a sacred value more violently opposed sacrificing Iran's nuclear program for conflict-resolution deals involving substantial economic aid, or relaxation of sanctions, than the same deals without aid or sanctions," they write. "In a 2005 study in the West Bank and Gaza, Palestinian refugees who held their 'right of return' to former homes in Israel as a sacred value more violently opposed abandoning this right for a Palestinian state plus substantial economic aid than the same peace deal without aid."



This dynamic is behind the paradoxical reality that the world finds itself in today: "Modern multiculturalism and global exposure to multifarious values is increasingly challenged by fundamentalist movements to revive primary group loyalties through greater ritual commitments to ideological purity."

But Atran and Ginges also offer some insights that could help to solve conflicts fueled by religious conviction. Casting these conflicts as sacred initially blocks standard business-like negotiation tactics. But making strong symbolic gestures such as sincere apologies and demonstrations of respect for the other's values generates surprising flexibility, even among militants and political leaders, and may enable subsequent material negotiations, they point out.

"In an age where religious and sacred causes are resurgent, there is urgent need for joint scientific effort to understand them," they conclude. "In-depth ethnography, combined with cognitive and behavioral experiments among diverse societies (including those lacking a world religion), can help identify and isolate the moral imperatives for decisions on war or peace."

Atran is also affiliated with Centre National de la Recherche Scientifique−Institut Jean Nicod, Paris, and with the John Jay College of Criminal Justice at the City University of New York.