Across history and cultures, religion increases trust within groups but also may increase conflict with other groups, a new analysis suggests. This could be why using monetary or material offers to deal with religious groups tends to backfire.

"Moralizing gods, emerging over the last few millennia, have enabled large-scale cooperation and sociopolitical conquest even without war," study researcher Scott Atran, of the University of Michigan, said in a statement. But these moralizing gods also come with sacred values, which "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."

The researchers analyzed data from previous studies, from all different populations, for their study which published today, May 17, in the journal Science.

The studies they analyzed include cross-cultural surveys and experiments in dozens of societies. They show that people who participate most in collective religious rituals are more likely to cooperate with others in their group, and that groups most intensely involved in conflict have the costliest and most physically demanding rituals to bring the group together and blind group members to exit strategies.

They also identify what they call the "backfire effect," which dooms many efforts to broker peace. In studies from Palestine, Israel, Iran, India, Indonesia and Afghanistan, they found that offers of money or goods 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," the researchers write in the paper. "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 push and pull between the conflict and cohesion that religion creates could be behind the seemingly backwards reality the world finds itself in today, they say. The modern world is seen as a challenge by fundamentalist movements, and pushes these groups together, making them stronger and more committed.

The researchers say that 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.

"In an age where religious and sacred causes are resurgent, there is urgent need for joint scientific effort to understand them," the researchers write. A better understanding of these cultures, "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."