Mark Twain once said, “Age is an issue of mind over matter. If you don’t mind, it doesn’t matter.” But researchers are finding that your gray matter certainly does mind. Research shows that your brain physically changes in specific ways with each passing year.

Findings reported in Current Biology demonstrate that despite the best efforts of our youth-obsessed society to conceal aging, there’s one part of the human body that always gives away your true age: the brain.

“We have uncovered a ‘developmental clock’ of sorts within the brain — a biological signature of maturation that captures age differences quite well, regardless of other kinds of differences that exist across individuals,” says Timothy Brown of the University of California, San Diego School of Medicine.

Researchers used magnetic resonance imaging to scan the brains of 885 people ranging in age from 3 to 20. Those brains scans helped identify 231 biomarkers of brain anatomy that can be used to assess an individual’s age with more than 92 percent accuracy; that’s within a year or two of actual age.

“The fact that we found a collection of brain measures that so accurately captures a person’s chronological age means that brain development, or at least certain anatomical aspects of it, is more tightly controlled than we knew previously,” Brown says. “The regularity in this maturity metric among typically developing children suggests that it might be sensitive to detecting abnormality as well.”