Across history and cultures, religion increases trust within groups but also may increase mistrust and conflict with other groups, according to studies by our research team and others analyzed in a special issue of Science magazine on human conflict.
Over the last few millennia, moralizing gods emerged, enabling large-scale cooperation, and sociopolitical conquest even without war. 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 our claim that religion increases trust within groups but may increase conflict with other groups, Jeremy Ginges and I 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 groups solidarity in common defense and blind group members to exit strategies. Secular social contracts are more prone to defection, we argue. The research also indicates that participation in collective religious ritual increases parochial altruism and, in relevant contexts, support for suicide attacks.
In what may be called the "backfire effect," which dooms many efforts to broker peace, we carried out studies with colleagues in Palestine, Israel, Iran, India, Indonesia and Afghanistan demonstrating that offers of money or other material incentives to compromise sacred values increases anger and violence toward a deal, the authors note. For example, 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.
In a 2008 experiment with Indonesian students in four madrassas (Muslim religious schools), those who regarded rule by Sharia (Muslim religious law) as a sacred value were more violently opposed to compromising Sharia rule in return for Western recognition of the Muslim Brotherhood plus significant economic aid than without aid. In a 2008 experiment with Indian Hindus, those for whom rebuilding a Hindu temple over the destroyed Babri Mosque was a sacred value more angrily opposed including a monument to the Mosque on the site when offered economic incentives to do so. 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. And in a 2005 study among Jewish settlers in the West Bank and Gaza, those who regarded Eretz Israel (God-given "Land of Israel") as a sacred value more violently opposed withdrawing from settlements for peace plus significant economic aid than for peace 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 we also also offer evidence 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.
Religion and sacred values inspire achievement of great virtue and great vice, in spiriting folk to glory or bending will to power. They arouse strong attitudes among believers and non-believers, and that can hinder deeper, nuanced appreciation of human conflict. In an age where religious and sacred causes are resurgent, there is urgent need for joint scientific effort to understand them, to help identify and isolate the moral imperatives for decisions on war or peace.