The vast majority of people avoid taking risks because avoidance is an evolutionary trait that helps us survive. Without a healthy fear of danger, risks could put us in harm’s way. Yet, others seem to have a tendency to seek out what’s extreme, whether it’s a physical adventure like mountain climbing or something simpler, like constantly craving spicy foods.

There are many environmental factors that contribute to risk-taking behaviors, such as one’s economic status or how safe they perceive a situation to be, but new research suggests tendencies for risk-taking and sensation-seeking may be hardwired in our brains. Studies have linked a propensity for taking risks to the brain’s reward system, and now, a new study suggests those of us who are the most likely to be take part in these activities actually have different brain structures from the rest of the population.

For the study, researchers from Harvard University, Yale University, and Massachusetts General Hospital used magnetic resonance imaging (MRI) to visualize and measure the sizes of different brain regions in over 1,000 people. The study’s participants included men and women, all between the ages of 18 and 35, who had no history of psychiatric disorders or substance dependence — two factors that can contribute to observable differences in brain structure.

To assess their inclination for risky behavior, the participants also completed a questionnaire that evaluated their individual needs for sensation-seeking, tendency to be impulsive, willingness to take risks, and likelihood of making quick decisions. Additionally, they reported how often they consumed substances like alcohol, tobacco, and caffeine.

By comparing the participants' questionnaires with their MRIs, the researchers discovered that participants who were more likely to seek high levels of stimulation and excitement had less grey matter — tissue that processes information — in the regions of the brain associated with decision making and self-control, compared to the rest of the participants.

"The findings allow us to have a better understanding of how normal variation in brain anatomy in the general population might bias both temperamental characteristics and health behaviors, including substance abuse," said Avram Holmes, the study’s lead author and a psychologist at Yale.

The researchers noted that the most observable lack of grey matter was in the anterior cingulate and middle frontal gyrus, two brain regions associated with the ability to regulate emotions and behavior. Reduced grey matter in these brain areas also correlated with above-average use of alcohol, tobacco, or caffeine.

While it’s still debatable whether individual brain differences can establish general neurological trends, the study’s results are promising. "A strength of the study is that they identify this relationship within non-substance using participants, implying that these variations are not merely the consequence of individual history of substance use," said Kristine Beate Walhovd, a professor of neuropsychology at the University of Oslo in Norway who was not involved in the study.

Source: Holmes A, et al. Journal of Neuroscience. 2016.