Across the United States—and in developed nations around the world—twenty-somethings […] are taking longer to finish school, leave home, begin a career, get married and reach other milestones of adulthood. These trends are not just anecdotal; sociologists and psychologists have gathered supporting data. Robin Marantz Henig summarizes the patterns in her 2010 New York Times Magazine feature:
“One-third of people in their 20s move to a new residence every year. Forty percent move back home with their parents at least once. They go through an average of seven jobs in their 20s, more job changes than in any other stretch. Two-thirds spend at least some time living with a romantic partner without being married. And marriage occurs later than ever. The median age at first marriage in the early 1970s, when the baby boomers were young, was 21 for women and 23 for men; by 2009 it had climbed to 26 for women and 28 for men, five years in a little more than a generation.”
These demographic shifts have transformed the late teens through mid twenties into a distinct stage of life according to Jeffrey Arnett of Clark University, who calls the new phase “emerging adulthood.”
Henig writes that some researchers think a lengthy preamble to adulthood might be “better-suited to our neurological hard-wiring” and that the general ambivalence of twenty-somethings—feeling that they are sort of adults, but not really adults— “reflects what is going on in the brain, which is also both grown-up and not-quite-grown-up.” Most recently, The Wall Street Journal ran an article recommending that concerned parents of twenty-somethings “chill out” because “recent research into how the brain develops suggests that people are better equipped to make major life decisions in their late 20s than earlier in the decade. The brain, once thought to be fully grown after puberty, is still evolving into its adult shape well into a person’s third decade, pruning away unused connections and strengthening those that remain, scientists say.”
Although these developmental changes continue far longer than researchers initially thought, they are not as dramatic in the twenties as they are in the teens. “In the twenties, the brain is definitely still changing, but it’s not rampant biological change,” explains Beatriz Luna of the University of Pittsburgh. “Most of the brain’s systems are good to go in one’s twenties.”
To reflect the ongoing structural changes in the adolescent and twenty-something brain, many journalists and scientists use words and phrases like “unfinished,” “work in progress,” “under construction” and “half-baked.” Such language implies that the brain eventually reaches a kind of ideal state when it is “done.” But there is no final, optimal state. The human brain is not a soufflé that gradually expands over time and finally finishes baking at age 30. Yes, we can identify and label periods of dramatic development—or windows of heightened plasticity—but that should not eclipse the fact that brain changes throughout life.
[W]idening the window of heightened neuroplasticity to encompass one’s twenties may have helped Homo sapiens adapt to rapid shifts in the climate. Unfortunately, as with many hypotheses in evolutionary psychology, scientists do not have a way to objectively test these ideas. Still, if we want to fully understand the brain, we cannot ignore the fact that it evolved in circumstances very different from our own.
For now, let’s put the brains of ancient twenty-somethings out of our minds. What about the twenty-somethings of today? Even if the brain’s developmental changes are more dramatic in the teens than in the twenties, the best available evidence suggests that a twenty-something’s brain boasts a little more adaptability than an older brain. Our twenties might represent a final opportunity to begin mastering a particular skill with a kind of facility we cannot enjoy in later decades. Should people in their twenties buckle down and choose something, anything, to practice while their brains are still nimble? Does the neuroscience suggest that, for all their freedom and fun, gallivanting twenty-somethings neglect their last years of heightened plasticity? Should parents encourage their 20-year-olds to shirk adult responsibilities lest they hamper an advantageous period of self-discovery and wild experimentation?
Solid neuroscience that can directly answer these questions does not yet exist.
Emerging adulthood is real—it’s happening, albeit to a small percentage of the world’s population. Whether we can, at this moment in time, meaningfully link this life stage to neuroscience seems a tenuous proposition at best. By itself, brain biology does not dictate who we are. The members of any one age group are not reducible to a few distinguishing structural changes in the brain. Ultimately, the fact that a twenty-something has weaker bridges between various brain regions than someone in their thirties is not hugely important—it’s just one aspect of a far more complex identity.
Interesting stuff. It wasn’t that long ago (geologically speaking) that human lifespans were so short that people were likely to be grandparents by their late thirties, assuming they live that long. Nowadays, many people don’t think about becoming parents until their thirties (or even later).