Brain development: The myth the brain "matures" when you're 25.
"When Leonardo DiCaprio’s relationship with model/actress Camila Morrone ended three months after she celebrated her 25th birthday, the lifestyle site YourTango turned to neuroscience...
YourTango was parroting a factoid that’s gained a chokehold over pop science in the past decade: that 25 marks the age at which our brains become “fully developed” or “mature.” This assertion has been used as an explanation for a vast range of phenomena. After 25, it’s harder to learn, a Fast Company piece claimed. Because “the risk management and long-term planning abilities of the human brain do not kick into high gear” until 25, an op-ed in Mint argued, people shouldn’t get married before then. In early 2020, Slate’s sex columnists Jessica Stoya and Rich Juzwiak fielded a reader question about the ethics of having sex with people under 25. “I am told, at least once every couple weeks, that if you’re under 25, you’re incapable of consent because your ‘frontal lobes are still developing,’ ” the distressed reader wrote.
Even some young people now regard age 25 as a turning point with seemingly magical properties. In one Reddit thread, a 24-year-old asks whether older, presumably wiser Redditors noticed changes after 25. (“I suddenly stopped finding Leonardo DiCaprio attractive,” one commenter quipped.) Others use the factoid to justify a range of bad decisions, from why college kids continued hosting keggers at the height of COVID to why some men are terrible at texting.
But this notion has taken on more urgent stakes, too. After the school massacre in Uvalde, Texas, a Washington Post article noted that the shooter had just turned 18 and been allowed to purchase guns legally, following a long line of men under 25 who’d committed similar atrocities. (The Post notes that the Parkland school shooter was 19, the Newtown shooter 20, and the Virginia Tech shooter 23.) Shouldn’t gun laws, experts argued, reflect that these young men don’t yet have fully developed brains?
So, what does happen to your brain at 25? And how did so many people get the idea that something profound happens at that specific age? The past two decades of neuroscience research provide some clues. A huge breakthrough in how we study brains and a few intriguing kernels from studies seem to have become the basis for a powerful idea that reaches far beyond the facts. The real answer to these questions may lie in a culture that’s uneasily grappling with what science can (and can’t) tell us about ourselves...
A 2016 study found that when faced with negative emotion, 18- to 21-year-olds had brain activity in the prefrontal cortices that looked more like that of younger teenagers than that of people over 21. Alexandra Cohen, the lead author of that study and now a neuroscientist at Emory University, said the scientific consensus is that brain development continues into people’s 20s.
But, she wrote in an email, “I don’t think there’s anything magical about the age of 25.”
Yet we’ve seen that many people do believe something special happens at 25. That’s the result of pop culture telephone...
There’s consensus among neuroscientists that brain development continues into the 20s, but there’s far from any consensus about any specific age that defines the boundary between adolescence and adulthood. “I honestly don’t know why people picked 25,” he said. “It’s a nice-sounding number? It’s divisible by five?”
Kate Mills, a developmental neuroscientist at the University of Oregon, was equally puzzled. “This is funny to me—I don’t know why 25,” Mills said. “We’re still not there with research to really say the brain is mature at 25, because we still don’t have a good indication of what maturity even looks like.”
Maturity is a slippery concept, especially in neuroscience. A banana can be ripe or not, but there’s no single metric to examine to determine a brain’s maturity. In many studies, though, neuroscientists define maturity as the point at which changes in the brain level off. This is the metric researchers considered in determining that the prefrontal cortex continues developing into people’s mid-20s.
That means that for some people, changes in the prefrontal cortex really might plateau around 25—but not for everyone. And the prefrontal cortex is just one area of the brain; researchers homed in on it because it’s a major player in coordinating “higher thought,” but other parts of the brain are also required for a behavior as complex as decision making... structural changes in the brain continue far past people’s 20s. “One especially large study showed that for several brain regions, structural growth curves had not plateaued even by the age of 30, the oldest age in their sample,” she wrote. “Other work focused on structural brain measures through adulthood show progressive volumetric changes from ages 15–90 that never ‘level off’ and instead changed constantly throughout the adult phase of life.”
To complicate things further, there’s a huge amount of variability between individual brains... “Some 8-year-old brains exhibited a greater ‘maturation index’ than some 25 year old brains”...
The concept of adulthood has been around much longer than neuroscience has been able to weigh in on it. Ultimately, we are the ones who must define the shift from adolescence to adulthood.
It’s no coincidence that the “mature brains at 25” factoid’s popularity has grown during a period of massive cultural change...
Believing that neuroscience reveals all is a trap many people fall into. In the 2005 Supreme Court case Roper v. Simmons, attorney Seth Waxman exemplified this bias toward neuro research while arguing that people younger than 18 should not face the death penalty. “The very fact that science—and I’m not just talking about social science here, but the important neurobiological science that has shown that these adolescents are—their character is not hard-wired,” Waxman argued. He contrasted social science with “neurobiological science,” implying that the latter is more important—irrefutable.
But the takeaways from neuroscience are rarely ironclad, which complicates the question of what role these studies should have in shaping policy around the rights and responsibilities of young people. Contrary to what Waxman and many others might believe, neuroscience can be just as squishy as psychology, a field some snobs argue isn’t even a science. Just like psychologists, neuroscientists must make judgment calls about how to collect and interpret data, and there are no right answers for how best to do that. Studying people is messy. “Despite being popularly viewed as revealing the ‘objective truth,’ neuroimaging techniques involve an element of subjectivity,” three health researchers who study adolescents wrote in a 2009 paper...
Researchers might be able to take a picture or video of the brain, but it’s not always clear what this really shows. The interpretation of neuroimaging is the most difficult and contentious part; in a 2020 study, 70 different research teams analyzed the same data set and came away with wildly different conclusions. Now that tens of thousands of fMRI studies have been published, researchers are identifying flaws in common neuroscience methods and questioning the reliability of their measures.
That’s not to say we should disregard the neuroscience—we just need to acknowledge its limitations. “We are giving neuroscience a starring role where it should have a supporting role,” Steinberg said.
The hard work of defining what maturity or adulthood really is falls on us as a society...
“Children and adolescents are not broken adults, but rather, they’re
functioning perfectly well for their developmental period,” Mills said.
They’re exactly where they need to be; the extra malleability in youth
prepares us to figure out our surroundings. “This is the time we’re
learning about our identity, other people, how we fit into the world—we
need the brain to be malleable,” she said. And while adolescence is
typically a time of big changes, reaching adulthood doesn’t mean the end
of that growth. You can make good or bad decisions at any age; you’ll
mature and regress throughout your life. You, like your brain, are
endlessly complex, and we’re so much more than brain scans will ever reveal."
