In addition to biophysical economics, from this paper it looks like there may also be biochemical economics: “The MAOA Gene Predicts Credit Card Debt”.

The study behind the article compared rates of credit card debt — i.e., having any credit card debt at all, not the amount of it — and found it to be associated with the presence of certain forms of MAOA. As far as the authors are aware, “this is the first article to show a specific gene variant is associated with real world economic behavior.”

MAOA is a gene that does something scientificky to brain chemistry. Variants of MAOA that are less efficient in the way they metabolize serotonin and other compounds have been associated with increased impulsiveness, aggression, and addiction. MAOA is basically one of the only genes I can actually name, because it crops up in pop science news articles every other month or so. (The only other gene I can name is sonic hedgehog, but that’s for more different reasons). Among many other attributes, MAOA’s been linked to increases in likelihood of joining a gang, or if in a gang using a weapon, rates of alcoholism, and suspecpability to sugar pills.

And now, possibly, it’s also been linked to rates of credit card debt. From the study:

Because credit card debt is a relatively expensive form of debt, our prior intuition is that, all other things being equal, it would be used more by those individuals seeking immediate gratification, displaying less consideration of future consequences, and reduced information processing. Hence, we hypothesize that people with less transcriptionally efficient alleles of the MAOA gene are more likely to accrue credit card debt.

The study concludes that “the results presented here refute the blank slate theory of economic behavior.” By ‘blank slate,’ the authors are not referring to the traditional blank slate theory, which holds that humans have more or less no natural imprinting, but rather to economic approaches that treat all humans as having the same natural imprint — the idea that we are all phenotypically Homo economicus.

While the idea sounds very tidy in theory — a gene that controls the rate of future discounting! I bet we can link this to the financial crisis somehow. Quick, someone check the DNA of Wall Street traders! — I’m not quite converted yet. It strikes me as being way too likely to result in the flourishing of the same just-so stories that evolutionary psych always falls prey too. Confirming that “impulsive people have more credit card debt” just isn’t particularly revolutionary. While linking it to a specific gene gives it an added dimension of coolness, it doesn’t actually add anything to economics on its own anymore than linking impulsive behavior to unstable childhoods does. So it’s neat, but economists don’t need to be rushing out to get their PhD’s in molecular biology any time soon.

-Susan