Sex Differences in Generosity.

Several behavioral economic games have been devised to study prosocial behavior. Two of the most famous ones are the two-person Ultimatum and Dictator games, hereafter referred to as UG and DG. In the UG, individual A is given a sum of money (e.g., $10) and asked to split this amount with individual B. Once a split is offered, individual B can either accept the split in which case they each receive their respective shares, or he/she can refuse it, and in this case neither receives any monetary amount. Classic economic theory posits that individual A should offer the smallest possible denomination. For example, if the ten dollars are available as 40 quarters then he/she should offer a quarter as from the perspective of individual B, the utility of receiving $0.25 is better than receiving nothing. The DG is similar to the UG with one key difference: individual B has no veto power. In this case, classic economic theory suggests that individual A should offer nothing!

Of course, the world inhabited by classical economists is different from the one that we live in. Hence, it is no surprise that countless studies have shown that people are much more generous than is expected by axioms of rational choice.
Several years ago, one of my former doctoral students (Tripat Gill) and I conducted experimental studies on both the UG and DG with the expressed intent of exploring whether the sex composition of the two players would have an effect on the amount offered by individual A. Of the four possible dyads, male-male, male-female, female-male, and female-female, which do you think yielded the highest and lowest offers? Whenever I ask this question to my students whilst lecturing, they come up with all sorts of interesting answers. Think about it for a moment prior to reading on.

Using an evolutionary psychological perspective, we theorized that in the context of a resource-based game (as is the case with both the UG and DG), men would be differentially generous to women (as a means of signaling generosity, altruism, etc.) whereas they would be maximally competitive when facing other men (as a form of intra-sexual rivalry). Women would be equally generous irrespective of the sex of the opposing individual B. Here is what we found (using $10 as the amount to be shared):

In the UG In the DG
Male-Male: $4.25 Male-Male: $1.23
Male-Female: $5.17 Male-Female: $2.15
Female-Male: $5.00 Female-Male: $1.87
Female-Female: $4.93 Female-Female: $2.55

In both instances, our hypothesis was confirmed, namely, only men display differential behavior (statistically significantly so) as a function of the sex of the person that they are facing. In both games, men gave more to women than they did to men. No such effect was found for women, as they did not differentiate on the basis of the sex of their opposing partner. This does not mean that women are not as competitive with their same-sex cohorts. Rather, they are less likely to express this rivalry using financial resources.

Did you predict these findings? If so, you might be a closeted evolutionary psychologist! ☺

Have a good Sunday. Ciao for now.

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