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Brain Maturity Extends Well Beyond Teen Years


I'm Tony Cox and this is TELL ME MORE from NPR News. Michel Martin is away. We'd like to spend this part of the program talking about the passage from childhood to adulthood and how that may be tougher for one distinct group of young people.

Most of the privileges and responsibilities of adulthood are legally granted by the age of 18. That's when you can vote, enlist in the military, move out on your own, but is that the true age of maturity? A growing body of science says, no. That critical parts of the brain involved in decision-making are not fully developed until years later at age 25 or so.

In a moment, we'll hear about how child advocates are hoping to use this research to change the laws about their foster care. But first, to learn more about adolescent brain development and maturity, we are joined now by neuroscientist, Sandra Aamodt. She is the coauthor of the book, "Welcome to Your Child's Brain: How the Mind Grows from Conception to College."

Sandra, welcome to the program. It's nice to have you.

DR. SANDRA AAMODT: It's nice to be here.

COX: Is this idea that the brains of 18 year olds aren't fully developed a matter of settled science?

AAMODT: Yes. The car rental companies got to it first, but neuroscientists have caught up and brain scans show clearly that the brain is not fully finished developing until about age 25.

COX: To not be too clinical in the spin that we put on this, what parts of the brain are we talking about and what changes happen between the ages of 18 and, let's say, 25?

AAMODT: So the changes that happen between 18 and 25 are a continuation of the process that starts around puberty, and 18 year olds are about halfway through that process. Their prefrontal cortex is not yet fully developed. That's the part of the brain that helps you to inhibit impulses and to plan and organize your behavior to reach a goal.

And the other part of the brain that is different in adolescence is that the brain's reward system becomes highly active right around the time of puberty and then gradually goes back to an adult level, which it reaches around age 25 and that makes adolescents and young adults more interested in entering uncertain situations to seek out and try to find whether there might be a possibility of gaining something from those situations.

COX: So this is important. Are the physiological changes in the brain, in terms of the development of young people, as significant and impactful as the cultural changes and environmental changes that they go through vis-a-vis peer pressure things of that sort?

AAMODT: Well, actually, one of the side effects of these changes in the reward system is that adolescents and young adults become much more sensitive to peer pressure than they were earlier or will be as adults.

So, for instance, a 20 year old is 50 percent more likely to do something risky if two friends are watching than if he's alone.

COX: Is there a difference between males and females with regard to their brain development, particularly in this age category?

AAMODT: Females' brains develop about on average two years earlier than male brains, so you're more likely to have a late developing male brain than female.

COX: So when females say they're smarter than guys, it really is true?

AAMODT: Especially around about the age of 15 or so. Yes.

COX: What does this mean? In a minute, we're going to be hearing from some advocates who think that the foster care system needs to be changed, in that in some states, when you reach the age of 18, you are booted out of foster care and their argument is based on some of the research that you are now citing that these young people are not really ready for the adult world.

What is the impact for someone who lives in a foster care kind of setting as far as their brain development is concerned?

AAMODT: One of the things that deprived childhood causes is problems with prefrontal cortex function, so somebody who has had an unstable home life is more likely to have trouble with planning and organizing behavior and with inhabiting impulses than somebody who has had a stable life.

COX: Would you say, based on the research that you are now citing, that it would make more sense to have the legal age become 25 instead of 18 or 21 in some cases?

AAMODT: I think it makes sense to have different ages for different functions. Obviously some 18 year olds are competent to go out into the world and handle things by themselves and some of them aren't. It would be nice if we had a little more flexibility to distinguish the two in the legal system.

COX: Final thing is, if these age limits are not adjusted to take into account the effect that the research has shown, what is the price - if I can put it that way - that society will end up paying down the road? I know that's a pretty large question. But another way of saying it is how important is it for us to address this and do something about it now?

AAMODT: Many of the costs of adolescents are actually - what we think of as the costs of adolescence, the risks of crime and car accidents and all the crazy things that adolescents do are actually more issues with young adults, people in the 18 to 25 age range, largely because they have more opportunities to get into these kinds of trouble because they have less parental supervision than the younger adolescents do.

COX: Sandra Aamodt is a neuroscientist and the co-author of "Welcome to Your Child's Brain: How the Mind Grows from Conception to College." She joined us from Capital Public Radio in Sacramento, California.

Sandra, thank you very much.

AAMODT: Thank you. Transcript provided by NPR, Copyright NPR.