Your personality says a lot about you. To categorize people by their disposition, psychologists have long relied on questionnaires. Now, however, researchers may be closing in on a tangible view of character in the brain. According to a recent study in PLoS One, resting brain activity varies with a person’s scores on a well-established personality test. When awake but not engaged in a task, each subject displayed activity patterns distinct from those found in someone with different traits.

Even at rest, the brain hums with neural activity. Re­search­ers think these resting-state patterns reflect how the brain typically operates when we interact with the world. “You can think of it as showing which connections in the brain are on speed dial and which ones aren’t,” says Michael Milham, a psychiatrist at the Child Mind Institute in New York City, who led the study.

Using functional MRI, the researchers monitored the resting state of 39 healthy participants and looked for regions that tended to activate together. How tightly coord­inated the activity was between a pair of regions—completely in sync or only somewhat the same—correl­ated with scores from one of five personality domains: neuroticism, extroversion, openness to experience, agree­ableness and conscientiousness. For example, neuroti­cism was associated with areas related to self-evaluation and fear. Other results were more surprising, suggesting an unexpected role in personality for the visual cortex and cerebellum—areas better known for visual processing and movement, respectively.

Because the brain activity only correlated with the traits, Milham says it is too soon to tell whether the patterns reflect the neural embodiment of personality. The findings, however, add to mounting evidence that studying the brain at rest may be a way to quickly approximate how an individual brain works and to zero in on circuits disrupted in disease.

This article was published in print as "Personality Circuits."