The so-called "warrior gene" may give its carriers better judgment when confronted with financial risk rather than make them prone to impulsive decisions.

Research published December 8 in the Proceedings of the Royal Society B is a step towards a more nuanced understanding of how variants of the gene MAOA--which specifies an enzyme, monoamine oxidase-A, that breaks down neurotransmitters such as serotonin--affect financial decisions.

The gene variant MAOA-L is associated with lower production of the enzyme and has been repeatedly linked to risky behavior. Previous studies suggested that carriers of MAOA-L are more likely to lash out when provoked, for example, or to be more prone to aggression when raised in high-stress environments. The new study, led by Cary Frydman at the California Institute of Technology in Pasadena, did more than just examine whether MAOA-L was associated with risky behavior. It also used computational probability models to assess the patterns of choices made by the individuals in the study and to distinguish between two ways in which genetics might be influencing such behavior--by affecting the value assigned to options ("value"), or by affecting the process by which the brain compares the values of two options ("choice").

The approach, Frydman says, was designed to "shed some light on the potential mechanisms in the brain which risk-taking passes through." To accomplish that, his team analyzed the genes of 83 men between the ages of 19 and 27 from different ethnic backgrounds, focusing on three gene variations -- two linked to risky behavior (MAOA-L and a variant of the gene DRD4, which encodes a receptor for the neuromodulator dopamine), and a third associated with anxiety and risk-avoidance (a variant of 5-HTT, which encodes a serotonin transporter). They also noted the presence of more common variations of those three genes, including the MAOA variant MAOA-H, which specifies higher levels of the enzyme.

The subjects did a financial decision-making exercise 140 times, choosing between a sure option (100 percent odds of ending up with $0, for example) or a gamble (a 50-50 chance of gaining $7 or losing $4, for example).

Frydman found that carriers of the 5-HTT variation linked to risk avoidance and the DRD4 polymorphism linked to risk-seeking showed no significant differences in judgment compared to peers with another variant of the same gene. But for carriers of the MAOA-L variant, there was a marked association. "At first blush, it looked like previous findings," Frydman says. MAOA-L carriers opted for the riskier choice in 41 percent of decisions, whereas carriers of MAOA-H did so 36 percent of the time.

Good choices

But when Frydman and his team analyzed their subjects' choices in the "value" model, they noted another trend: when faced with a potentially winning gamble, subjects carrying MAOA-L made the optimal choice more often than those with MAOA-H. In other words, those with the "warrior gene" weren't making risky financial decisions because they were rash, but because they were adept at rooting out the better choice.

"It shows that risky behavior is not always counterproductive and it's not always suboptimal," Frydman says.

The study does have limitations. Among these, the authors note that 19 participants were excluded from the computational modeling because, for some at least, the answers were too perfect, suggesting that they were following an "offline" rule instead of responding instinctively, making it difficult to model their decision-making accurately.

Benedetto De Martino, a neuroeconomist at University College London, is also concerned that the control for ethnicity might not have fully accounted for the fact that gene variations influence behavior differently in different ethnic groups, but nonetheless lauds the novel approach. "When you have a computational model in which you have very simple and clear parameters, you can tell if something is more than a generic association," he says.

John Coates, who studies the role of hormones in financial risk-taking at the University of Cambridge, UK, says the research marks a development for the still-nascent field of neuroeconomics: "It's really important to distinguish between returns and risk-adjusted returns, and this is the first study I've seen that really tried to get at the difference at the genetic level."