Brain size matters, data suggest

LITTLE ROCK — Does the size of your brain - or, more specifically, different regions of it - say anything about your personality? According to a new study, there’s a chance it does.

Using magnetic resonance imaging and personality questionnaires, Colin DeYoung, a University of Minnesota psychology professor, and his colleagues investigated the biological basis of what psychologists know as the Big Five personality traits: extroversion, agreeableness, conscientiousness, neuroticism and openness/ intellect. Their three years of research showed that certain brain regions had significantly different sizes depending on the self-reported strength of a particular personality trait.

Researchers used MRIs to compare the brains of 116 healthy adults to the “reference brain” of a person whose personality traits seemed average, according to an article published in the June issue ofPsychological Science. Using computer software, DeYoung said researchers “stretched or squished” individual brain scans to match them with the reference image, and then noted the size of the different regions of each brain.

MRI scans of self-described extroverts revealed a significantly larger medial orbitofrontal cortex, the area just above and behind the eye sockets. This area is involved with keeping track of rewards, researchers said.

The posterior cingulate cortex and superior temporal sulcus were larger in people who identified themselves as having many characteristics associated with agreeableness. That area is associated with understanding the actions and mental states of others, researchers said. Above-average conscientiousness was associated with a larger region of the lateral prefrontal cortex, which is involved in planning and voluntary control of behavior.

Self-described neurotics,who tended to experience negative emotions, had smaller brain volumes in areas known to regulate emotion. Neurotics also had a significantly larger midcingulate gyrus, a region that detects pain and error.

The only trait without a significant neuroanatomical relationship, according to the report, was openness/intellect, which researchers said reflects imagination, curiosity, and artistic and intellectual interests.

Despite finding a correlation between brain structure and personality, DeYoung said that genes and the environment play important roles. “Personality doesn’t change easily, but it can change,” he said in an e-mail. “When it does, that change is accompanied by changes in the brain.”