Scientists have found that the size of different parts of people’s brains correspond to their personalities. For example, conscientious people tend to have a bigger lateral prefrontal cortex, a brain region involved in planning and controlling actions.
Psychologists commonly break down all personality traits into five factors: conscientiousness, extraversion, neuroticism, agreeableness, and openness/intellect. Researchers Colin DeYoung at the University of Minnesota and colleagues wanted to know if these factors correlated with the size of structures in the brain.
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The medial orbitofrontal cortex, whose activity is highlighted in the brain scan above, was found to be significantly larger in very extroverted people. (Image courtesy J. O'Doherty et al., Caltech)
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The scientists gave 116 volunteers a questionnaire to describe their personality, then gave them a brain imaging test that measured the relative size of different parts of the brain. Several links were found between the size of certain brain regions and personality. The research appears in the journal Psychological Science.
For example, “everybody, I think, has a common sense of what extroversion is – someone who is talkative, outgoing, brash,” said 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 extroversion.
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 extroverts. Indeed, they found that one of those regions, the medial orbitofrontal cortex – just above and behind the eyes – was significantly larger in very extroverted study subjects.
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, the researchers found.
“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,” said DeYoung. He points out, though, that this doesn’t mean 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.
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