Some of [Gary] Becker's most compelling early research concerned altruism. He argued, for instance, that the same person who might be purely selfish in business could be exceedingly altruistic among people he knew -- although, importantly (Becker is an economist, after all), he predicted that altruism even within a family would have a strategic element.
Summers empirically demonstrated Becker's point. Using data from a U.S. government longitudinal study, they showed that an elderly parent in a retirement home is more likely to be visited by his grown children if they are expecting a sizable inheritance.
But wait, you say: maybe the offspring of wealthy families are simply more caring toward their elderly parents?
A reasonable conjecture -- in which case you'd expect an only child of wealthy parents to be especially dutiful. But the data show no increase in retirement- home visits if a wealthy family has only one grown child; there need to be at least two. This suggests that the visits increase because of competition between siblings for the parent's estate.
This illustrates an interesting problem in defining altruism not just as good acts, but good acts done selflessly:
How can we know whether an act is altruistic or self- serving? If you help rebuild a neighbor's barn, is it because you're a moral person or because you know your own barn might burn down someday? When a donor gives millions to his alma mater, is it because he cares about the pursuit of knowledge or because he gets his name plastered on the football stadium?
Sorting out such things in the real world is extremely hard. While it is easy to observe actions, it is much harder to understand the intentions behind an action.
After an interesting discussion of several lab experiments, researchers conclude that true altruism (if it exists as all) is elusive as a unicorn or Nessie:
If John List's research proves anything, it's that a question like "Are people innately altruistic?" is the wrong kind of question to ask. People aren't "good" or "bad." People are people, and they respond to incentives. They can nearly always be manipulated -- for good or ill -- if only you find the right levers.