Altruism in Experiments

We call an act altruistic when it is a sacrifice that benefits others. We discuss how experiments have demonstrated that altruistic choices appear to follow the same regularity conditions as those assumed for private goods. In particular they vary rationally in response to changes in prices and circumstances. We show how experiments have distinguished between different economic models of how concern for others enters utility functions, and have explored the implications of those models for charitable giving, labor markets, and trust. We also discuss the experimental evidence for differences in altruism by gender, and work on altruism’s cultural, developmental, and neural foundations. Unlike experiments on markets or mechanisms, experiments on altruism are about an individual motive or intention. This raises serious obstacles for research. How do we define an altruistic act, and how do we know altruism when we see it? The philosopher Thomas Nagel provides this definition of altruism: ‘By altruism I mean not abject self-sacrifice, but merely a willingness to act in the consideration of the interests of other persons, without the need of ulterior motives’ (1970, p. 79). Notice that there are two parts to this definition. First, the act must be in the consideration of others. It may or may not imply sacrifice on one’s own part, but it does require that the consequences for someone else affect one’s own choice. The second aspect is that one does not need ‘ulterior motives’ rooted in selfishness to explain altruistic behaviours. Of course, ulterior motives may exist alongside altruism, but they cannot be the only