When the great author and playwright J. M. Barrie was 6 years old, his brother David died in an accident. Barrie's mother, making no attempt to hide the fact that David had been her favorite child, collapsed into a crippling depression, often refusing to leave her bed. Once, as Barrie entered his mother's room, he heard her ask hopefully, "Is that you?" He knew she meant David. "No, it's not him," he answered; "it's just me."
His mother's only consolation, Barrie later said, was her insistence that he remain a little boy forever, never to grow up and leave her. She held onto this obsession until the day she died, and Barrie never forgot it, either. Nearly 40 years later, he created his most enduring character: Peter Pan.
In the book by that name, Barrie tells a story about the character Wendy Darling: When Wendy was 2 years old, she picked a flower from the garden and ran to show it to her mother, who put her hand to her heart and cried, "Oh, why can't you remain like this for ever!"
"This was all that passed between them on the subject," Barrie writes, "but henceforth Wendy knew that she must grow up. You always know after you are two. Two is the beginning of the end."
Even for those of us with more optimistic views on adulthood, there's no denying that our bodies and minds change as we grow up. Often that's a good thing: We learn patience and self-control; we develop an appreciation for books and drinks we hated as teenagers; we grow more adept at our favorite hobbies. And our brains are gaining skills, too: As the birth of new neurons slows down, those cells are learning to communicate more efficiently.
Take connectivity, for example. When you were born, your brain was wired for maximum adaptability: Many hubs of fairly random brain activity interacted closely with one another, chiming in to help you make sense of the strange new world you were exploring. But by your late 20s your brain had rewired itself into a team of specialists, each of them still in communication with the others but honed by experience to handle its own business: keeping your attention on a task, searching your memories and so on.
As you continue to age, those networks and hubs will specialize even further, until, as a recent study in the journal PLOS ONE discovered, many of them will have learned multiple ways to attack a problem -- by working with their close neighbors, or by reaching out to other areas of your brain. So it makes sense that learning a second language and staying physically fit help keep your mind young: Both of them challenge your brain to stay adaptable, to tackle tricky situations head-on.
Meanwhile, another recent study found that as you age, your brain's functional networks will become less random, more predictable, in their connectivity (until very advanced age, when they fall into randomness again). This doesn't mean you can't teach an old dog new tricks, but it does mean the old tricks keep getting easier to perform, while burning less and less mental energy. With age comes wisdom, even for neural networks.
Wendy Darling's mother might've been dismayed that her daughter couldn't stay the same forever, but then nothing really does. I've learned and changed since I started writing this artlcle; you're a different person now than you were when you started reading it. Even the act of resisting change causes changes in your body and mind; every second, they're learning to get better at resisting. Or, if you'd rather, you can teach them to get better at adapting. Whichever you prefer, your brain is all yours -- and so's the choice of how to train it.