From Reason.com:

Does Religion Make People Nicer?
Only if they think Sky Big Brother is watching
Ronald Bailey | October 7, 2008

In his new movie Religulous, comedian Bill Maher makes wicked fun of the religiously credulous. But it turns out that the folks who believe in talking snakes and seventy-two virgins per martyr may be on to something. As whacky as some dogmas are, religions do appear to encourage generosity and honesty. At least that is the claim made in a fascinating review article, “The Origin and Evolution of Religious Prosociality” (subscription required) published in the current issue of Science.

Evolutionary biologists argue that there’s nothing surprising about genetically related individuals making sacrifices for their kin: They are helping some of their own genes get passed along to the next generation. But what might cause people to make sacrifices for the good of unrelated strangers? Here, according to University of British Columbia social psychologists Ara Norenzayan and Azim F. Shariff, religion plays a key role.

The authors have winnowed three decades of empirical evidence looking for examples of religious prosociality, which they define as “the idea that religions facilitate acts that benefit others at a personal cost.” Specifically, their hypothesis is that religion encourages people to sacrifice their individual fitness for the benefit of unrelated individuals or for their group. For example, young men may risk sacrificing themselves in war to protect their tribe. So how does religion encourage prosociality? The answer is that being watched by a Big-Brother-in-the-Sky tends to make believers nervous about being selfish.