Study finds that, developmentally speaking, 18-year-olds are not quite adults.

You’re allowed to vote, to buy cigarettes, to marry, to fight in a war, to download porn on the Internet and, in some states, to be executed. But at the age of 18, is your brain really all grown up? Psychologists at Dartmouth say, “No.”

Abigail Baird, assistant professor of psychological and brain sciences published a study in an online issue of Human Brain Mapping that provides evidence that there’s ongoing structural development in the brains of 18-year-old college freshmen.

The research could have a profound effect on our conceptions of maturity, says Daniel Ansari, assistant professor of education at Dartmouth.

“[The study] shows how much change still goes on after what we define culturally as adulthood.”

While it has always been intuitively clear that people go through behavioral changes after age 18, the anatomical picture is fuzzier, said Craig Bennett, a graduate student who coauthored the paper. Recent studies by researchers like Jeffrey Arnett, author of the book Emerging Adulthood: The Winding Road from the Late Teens through the Twenties, have confirmed early adulthood as a continuing period of development.

“We sought to investigate whether there were any changes in the brain that supported the work of these other researchers,” said Bennett. “Was there a brain-based explanation for the changes occurring in emerging adulthood?”

Baird and Bennett scanned 17 brains belonging to 18-year-old Dartmouth students, picking the subjects randomly from a list of incoming freshmen. Each participant was scanned twice, the second scan taking place six months after the first.

The researchers also scanned 17 older subjects—ranging in age from 25 to 35—for a control group. To make sure the controls accurately reflected the experimental subjects, all of them had to be Dartmouth students or researchers, and they all had to have moved away from home after high school.

The results showed significant development in the parts of the brain relating to self-perception—both the physical self and the emotional self—and inhibitory control, areas responsible for integrating cognitive and emotional processes. The authors suggest that the maturation comes in response to environmental changes common to 18-year-old college students: the cognitive demands of leaving home, associating with new kinds of people and figuring out the rules to beer pong.

“For many, the freshman year in college is one of the biggest changes to occur in their lives,” Bennett said. “They are separated from their homes and the support structures that were familiar. They are in a new environment filled with new social challenges that must be addressed. All this is happening during a period where the brain is still developing and moving toward maturity.”

While the study blurs the line where a person progresses from child to adult, Bennett doesn’t think 18-year-olds should be considered adult-sized children.

“It isn’t so much that an 18-year-old brain is incapable of performing certain adult-like functions,” he said. “Rather, it is more correct to state that they are getting more efficient and consistent at conducting themselves as an adult.”

Originally published February 10, 2006


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