Here is an interesting read from Paul Bloom, a professor of psychology at Yale University. It poses the question of whether being religious correlates with being nice, or conversely, does being an atheist make you mean? The results are one of those things that seem pretty obvious in retrospect. The correlation is not really about religiosity, but about degrees of connectedness to social groups. People who feel connected tend to be nicer than those who feel isolated. Well duh. The serial killer is always the silent loner.
Another interesting observation which can be extrapolated from this study is that the idea of God watching you, or paying for your sins in the afterlife would seem to not be nearly the motivating factor that the judgment of your social group is. This would explain why people who belong to fringe religious groups (e.g. Islamic Terrorists) are capable of being evil when motivated by their peers. It also explains why so many people who are model Christians on Sunday morning are capable of being complete PITAs when they think no one they care about is looking.
What’s not clear from this study is how you really quantify or define that social connection. I would speculate that it doesn’t relate to the size of the group or number of groups to which you belong, or your activity level within any of these groups. Rather it is the level to which your ego is tied up in the group. If the group is part of your identity. If belonging to the group and being accepted by the group defines a portion of your self worth. If the group is part of your raison d’etre. Then, it will regulate your behavior. Otherwise, the group is just padding your résumé. I would also contend that the “group” could be a single individual if the ego bond is strong enough. For some, being a model parent, partner, or friend may be sufficiently binding to moderate your behavior and make you be nice.
All of which I guess means that the old adage, “No man is an island” should be updated to say, “No nice man is an island.”