Exploring exploration

In the face of uncertainty about the outcomes of our decisions, how do we choose between sticking with what we've been doing and trying a new approach? In a study published online this week in Nature Neuroscience, Michael Frank and colleagues show that a gene regulating dopamine breakdown is predictive of how likely people are to explore alternative strategies when uncertain about current strategy.

Previous studies had found that the COMT gene in the prefrontal cortex, the region of the brain directly behind the forehead, regulates levels of the neurotransmitter dopamine. People with one form of this gene ― valine-encoding ― have a more efficient version of the COMT enzyme, resulting in lower dopamine levels, than those with another form of the gene ― methionine-encoding.

Frank and colleagues asked participants, genotyped for their COMT gene, to perform a simple task of deciding when to stop a clock. Subjects were given points based on the timing of their responses. However, they were not told whether an early or late response would be more rewarding, and had to discover the best response strategy by trial and error. When participants were uncertain about what the best strategy to garner points was, those carrying the methionine type gene were more likely to explore alternative strategies than those carrying the valine type gene.

The scientists created a mathematical model to quantify how much people with the different types of COMT are likely to explore alternate strategies with different levels of uncertainty. Their work reinforces the body of evidence that suggests that genes controlling dopamine function in the brain critically affect our decision-making.