Why Do People Help Complete Strangers?

Would you help someone who was just hit by a car? Someone who you do not know, and will never see again? Of course you would (I hope). But why?

It's not because it's the "right thing to do" because that answer only changes the phrasing the question; i.e., Why is helping someone the right thing to do?

But here are some possible reasons:

A) Conscious reciprocity. Some people like the gratification of hearing a big "thank you"; it makes them feel good. This implies that the motivation to help was not altruism, but instead was a selfish desire for gratification. Or, more cynically, one might help a stranger for a monetary award, or even for an outside chance of having sex. (If that sounds a bit "harsh", then consider who would get more assistance: An attractive young woman or a fat middle-aged man.) Nevertheless, the desire for reciprocity "works" in that the helper and the victim both come out ahead compare to an identical situation where the helper would otherwise keep walking.

B) Irrational justifications. Many people are self-deluded into believing things that don't hold up well to logic. An example might be: "If I were hit by a car, I would want someone to help me!" Though that sentiment might be true, the logic doesn't work; i.e., helping a complete stranger has no bearing on whether a different complete stranger will help you someday. Similarly, some people might think, "That could be my parent/child!" But it isn't your parent or child -- and your helping them does not increase the chances that your relatives will be similarly helped someday. Still, the justifications, though not rational, help everyone.

C) Social or religious pressures. This works to the extent that your society or religion does not instruct you to instead kick the victim -- or worse, run your car over him to begin with.

D) No idea why; "I just did it". This does away with all reasoning and assumes an adaptive biological trait that somehow increases procreation among those who help others -- which in turn increases this trait's frequency in the population. That is: You help others because an ancestor with this trait, a long time ago, had lots of children. (The assistance-for-sex idea might seem a bit more plausible now...)

Two more things to note:

1. None of the above reasons are related to altruism -- or at least of the moral posturing variety. ("I am selflessly sacrificing so that someone else might have a better life etc., etc., etc.)

2. It was an easy example; the helper's cost was minimal, and the victim's benefit was great. There's a big difference between people who, on the scene, would be willing to punch "911" on their cell phones -- and people who make anonymous kidney donations. The real altruists are on that kidney donation line.