For example, conscientious people tend to have a bigger lateral prefrontal cortex, a region of the brain involved in planning and controlling behavior.
Although personalities are often complex, psychologists broadly classify personality traits into five factors: conscientiousness, extraversion, neuroticism, agreeableness, and openness/intellect.
In the study, Colin DeYoung at the University of Minnesota and colleagues wanted to know if these personality factors correlated with the size of structures in the brain.
Investigators asked 116 volunteers to answer a questionnaire to describe their personality. This was followed by a brain imaging test that measured the relative size of different parts of the brain.
A computer program was used to warp each brain image so that the relative sizes of different structures could be compared. Several links were found between the size of certain brain regions and personality.
The research appears in Psychological Science, a journal of the Association for Psychological Science.
For example, “Everybody, I think, has a common sense of what extraversion is – someone who is talkative, outgoing, brash,” says DeYoung.
“They get more pleasure out of things like social interaction, amusement parks, or really just about anything, and they’re also more motivated to seek reward, which is part of why they’re more assertive.”
That quest for reward is thought to be a leading factor in extraversion. Earlier studies had found parts of the brain that are active in considering rewards. So DeYoung and his colleagues reasoned that those regions should be bigger in people who are more extraverted.
Indeed, they found that one of those regions, the medial orbitofrontal cortex – located just above and behind the eyes – was significantly larger in study subjects with a lot of extraversion.
The study found similar associations for conscientiousness, which is associated with planning; neuroticism, a tendency to experience negative emotions that is associated with sensitivity to threat and punishment; and agreeableness, which relates to parts of the brain that allow us to understand each other’s emotions, intentions, and mental states. Only openness/intellect didn’t associate clearly with any of the predicted brain structures.
“This starts to indicate that we can actually find the biological systems that are responsible for these patterns of complex behavior and experience that make people individuals,” says DeYoung.
He points out, though, that this doesn’t mean that your personality is fixed from birth; the brain grows and changes as it grows. Experiences change the brain as it develops, and those changes in the brain can change personality.