What economics misses

Over at the Evolutionary Psychology Blog, Robert Kurzban has posted a fairly harsh take-down of a paper by Roy Baumeister and Kathleen Vohs.

The paper proposes that as sex is a scarce resource offered by women, it can be subject to economic analysis. From this, they come to some predictions such as men offering women other resources for sex.

Kurzban notes that the paper is a rehashing of work that dates back to Robert Trivers in 1972 and Don Symons in 1979. While I tend to agree with Kurzban’s assessment of the novelty of the paper (although I need to give the paper some more time), he then makes a more interesting point. Kurzban notes that the paper is novel as it cannot explain the coarsest patterns of human sexuality:

Unlike Parental Investment Theory and Sexual Strategies Theory, the “new” “theory” can’t explain the origin of the preferences nor any of their texture. For instance, Baumeister and Vohs discuss the value of female virginity, but one needs Parental Investment Theory to explain this male preference. They assert that having sex for the first time “signifies the commencement of adult sexual activity and therefore may be an especially important step and choice,” a non-explanation for the value that men place on female virginity. The issue of paternity certainty, of course, makes this crystal clear.

They also claim that their theory can explain the data on infidelity because “Female sexual infidelity involves giving away a precious resource that the husband wants for himself, whereas male sexuality has no inherent value.” (p. 348). However, their theory doesn’t say anything about sexual exclusivity; nothing in the model says that female sexuality is something men want to monopolize, only something that men want to consume. Again, one requires Parental Investment Theory to explain the proximate psychology.

Their theory can’t explain the most basic aspects of mate preferences, such as why sex with women of a particular age is favored over sex with the elderly, or any of the other preferences that have been well documented. In short, the theory is unable to accommodate existing findings, and “predicts” – really, post-dicts –  empirical patterns well explained by other theories.

Without the evolutionary biology underpinning the analysis, the economic model is at best predictive. In contrast, an evolutionary analysis can be more successfully predictive and incorporate an understanding of what is occurring. This is not just an issue in this paper, but applies to many areas in economics - right down to the basic question of what a person is seeking to achieve. As evolutionary biology seeps into the practice of economics, we will fill some of those gaps.