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Neuroticism — the personality trait that makes people both more anxious and more sensitive — can manifest itself in some less-than-obvious ways. More neurotic people often have trouble staying focused at work, for example. They’re more likely to choose friends who look like them, and to see faces in objects. They also get the biggest mood boost from being nice.

And, according to a study recently published in the journal Social Cognitive and Affective Neuroscience, they have brains that look distinctly different from those of their less neurotic counterparts. The study design was simple: Volunteers filled out a questionnaire measuring their levels of each of the Big Five personality traits — neuroticism, agreeableness, openness, extraversion, and conscientiousness — and then let the researchers scan their brains, with a focus on the appearance of the the outermost layer, called the cortex.

When the study authors analyzed the results, they found a few key links: People who scored higher on openness tended to have thinner and smoother cortices, while those who scored high on neuroticism had cortices that were thicker and more wrinkled.

As New Scientist explained, the study results make sense when you consider how and why our personalities develop as we grow up:

Folds and wrinkles are thought to increase the surface area of the brain, but make the cortex thinner. The cortex continues to stretch and fold throughout childhood and adolescence, and into adulthood. As we grow up, people generally become less neurotic, and more conscientious and agreeable.

“Our work supports the notion that personality is, to some degree, associated with brain maturation,” study author Roberta Riccelli, a cognitive scientist at Italy’s Magna Graecia University, told the magazine. In other words, maturity — a state we often associate with both conscientiousness (which makes people forward-thinking and organized) and agreeableness (which makes them sympathetic and kind) — may be partly the result of lived experience, but it may also be a side effect of the way your brain physically ages over the years. If working to change your personality seems like too much effort, there’s some comfort in knowing that time is on your side.