If people are so self-interested, why do they give their money away to charities? One possibility is that people care about the level of the public good their donations provide. But this is not a good explanation: free-riding typically dominates donating even for people who care a great deal about the good in question, and even in groups that are substantially smaller than those in which people contribute. An alternative explanation for giving is that the benefit comes from the donation itself, not from the good it buys. This idea is ancient. In the Old Testament, God promises those giving to the temple that he will

We use a within-subjects experiment with math and word tasks to show that relative performance feedback moves high-ability females toward more competitive forms of compensation, moves low-ability men toward less competitive forms, and eliminates gender differences in choices. We also examine females across the menstrual cycle and find that women in the high-hormone phase are more willing to compete than women in the low-hormone phase. There are no significant differences between choices after subjects receive feedback. Thus, biological differences lead to economically significant differences, but the impact of those differences can be lowered through relative performance information.

This paper uses an updated and revised panel data set on ambient air pollution in cities worldwide to examine the robustness of the evidence for the existence of an inverted U-shaped relationship between national income and pollution. We test the sensitivity of the pollution-income relationship to functional forms, to additional covariates, and to changes in the nations, cities, and years sampled. We find that the results are highly sensitive to these changes, and conclude that there is little empirical support for an inverted U-shaped relationship between several important air pollutants and national income in these data.

GARP for Kids: On the Development of Rational Choice Behavior by William T. Harbaugh, Kate Krause and Timothy R. Berry. Published in volume 91, issue 5, pages 1539-1545 of American Economic Review, December 2001