http://www.cell.com/current-biology/abstract/S0960-9822%2815%2901167-7 (you'll have to pay for the full text)
Prosocial behaviors are ubiquitous across societies. They emerge early in ontogeny [ 1 ] and are shaped by interactions between genes and culture [ 2, 3 ]. Over the course of middle childhood, sharing approaches equality in distribution [ 4 ]. Since 5.8 billion humans, representing 84% of the worldwide population, identify as religious [ 5 ], religion is arguably one prevalent facet of culture that influences the development and expression of prosociality. While it is generally accepted that religion contours people’s moral judgments and prosocial behavior, the relation between religiosity and morality is a contentious one. Here, we assessed altruism and third-party evaluation of scenarios depicting interpersonal harm in 1,170 children aged between 5 and 12 years in six countries (Canada, China, Jordan, Turkey, USA, and South Africa), the religiousness of their household, and parent-reported child empathy and sensitivity to justice. Across all countries, parents in religious households reported that their children expressed more empathy and sensitivity for justice in everyday life than non-religious parents. However, religiousness was inversely predictive of children’s altruism and positively correlated with their punitive tendencies. Together these results reveal the similarity across countries in how religion negatively influences children’s altruism, challenging the view that religiosity facilitates prosocial behavior.
We know how in human sciences the perspective of the observer can affect the result of the investigation and I bet all the authors of this study are atheist.
However, even if the results might be controversial, this study gives a powerful blow against all religions. When believers give up on trying to prove that their god exists (not other people's god or gods, of course), the next argument is on the social benefits of religion (nothing like putting the fear of god in the bones of the oppressed to put them in order). Well, even the most basic ones are rejected by this study, on the contrary.
Of course, the study has to be attacked by religious people. It could threat the job of many priests of hundred of religions that sell (directly or indirectly, all religious institutions are paid by societies) tickets to "heaven".
It would be important to have more studies like this, to confirm the results and determine what are the exact causes beyond them. I have no doubt that atheist are much more tolerant, they don't assume they have the truth in their pocket. And since they think there is no life but this one, they completely reject the idea of punishing or killing others for any religious moral code, for any religious idea or to receive any after life "payment". That removes the "fun" of many aggressive attitudes and, especially, wars.
Actually, saying to someone "do this and god will pay you", is like attributing debts to god. "I can't pay you, but god will, believe me". Not even the scammers on this forum would dare to try this line.