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Can You Tell How Mature Your Kid's Brain Is by Looking Into It?

How much have we learned about development from neuroimaging?

Key points

  • fMRI imaging records brain activity and measures blood flow. It's easier to do it than analyze or interpret the results.
  • The assumption that the 25-year-old brain is fully mature is widespread, but not necessarily true. We don't know what a mature brain looks like.
  • How we talk about maturity and adulthood has broad implications for social policy.
  • Neuroplasticity explains the brain's capacity to create new neurons and build new networks at any age.

Lately, several of my coaching clients have reflected on the shortcomings of their young adult kids. They question whether their inability to plan for the future, lack of consideration for others, poor decision-making, difficulties in handling negative emotions, or lack of impulse control are because their brains aren't yet capable of successfully carrying out those functions. Often parents who are frustrated by their offspring’s slow and sometimes painful path to maturity cling to the widely accepted belief that brain development is not complete until age 25 and take some comfort from the hope that as soon as that birthday is reached, their kids will automatically grow up; or at least, their brains will, and their behavior will reflect it.

Blame it on neuroscience, particularly the use of fMRI imaging to capture detailed images of the brain’s structure by recording brain activity and measuring changes in blood flow in real-time as people respond to various stimuli like sound and pictures. As children grow older, their prefrontal cortex, which is the source of cognitive control, undergoes physical changes in the bundles of nerve fibers responsible for communication across the brain area. Well into the 20s, this white matter, as neuroscientists call it, continues to increase the capacity for learning. Additionally, brain function, as well as size, can be observed across developmental periods by fMRI; in a recent study of late adolescents ages 18 to 21, when faced with negative emotions, activity in the prefrontal cortices was more similar to that of younger teenagers than it was in people over 21. Yet, as Patricia Cohen, a researcher at Emory University who authored that study reported, “There’s nothing magical about age 25; people’s brains continue to develop well into their third decade.” As Kate Mills, a developmental neuroscientist at the University of Oregon said, “We’re still not there with research to say when the brain matures because we still don’t have a good indication of what maturity even looks like.” There’s no single metric to define when changes in the brain level off, though most researchers believe development continues well into the 20s.

The interpretation of neuroimaging is the most difficult task of brain scientists; the same data can lead to very different conclusions, and how we talk about maturity and adulthood is a narrative of which science is only one element. The widespread acceptance of the assumptions that the 25-year-old brain is fully mature, regardless of emotional as well as cognitive development, has many implications for social policy, especially in the criminal justice system, gun ownership, reproductive rights, gender-affirming surgery, and other medical procedures, including the right to die or even sign a DNR.

Parents who’ve hoped that reaching the age of 25 will magically transform their young adult children into fully functioning adults who are able to curb their impulses, make wiser and more informed decisions, plan for the future, keep their commitments, and take their rightful place in society may be disappointed when all or none of these happy events occur on schedule. It’s more helpful to suggest that because the brain is malleable not just until that milestone but beyond, maturity and regression are lifelong processes. It’s not only teenagers and emerging adults who keep learning and growing; neural plasticity doesn’t solidify at age 25, or any other age. The capacity to learn new things isn’t a spigot that’s automatically turned off at maturity; the brain continues developing and evolving in response to life experiences. While it may be harder to learn a new language or gain fluency and skill in any other activity that requires cognitive neuroplasticity, it’s far from impossible. Every new experience and the bit of learning that results from it rearranges the brain’s synapses, creates new neurons, builds new networks, and demonstrates the brain's capacity to be shaped, molded, or altered to adapt or change over time, even when the organ itself stops developing.

“I’m too old to learn new things,” my mother used to say when I tried to share my enthusiasm or knowledge about everything from computers to pastry-making. Yet she continued to attempt many new activities that surprised and even daunted me. She learned Braille and sign language in her 60s because one of her friends had lost her sight and another her hearing. She took a class in CPR after my father had his first heart attack. And when I use the same excuse to remain ignorant about other things I really should know, my kids roll their eyes and tell me I’m channeling their grandmother. Most of the time that’s enough to make me at least try, even though, as I invariably tell my son, I don‘t want to live in a world where I have to change my own tire.

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