No one denies that age has costs. A healthy adult’s brain contains approximately 100 billion neurons (nerve cells), some of which die off with age. “For all of us, there’s undoubtedly a very slow degeneration,” says neurologist Arnold Scheibel, turning 82 on Jan. 18 and still hard at work at UCLA. The loss is drastic in people with Alzheimer’s, but no big deal in health individuals. And other parts of the brain actually keep developing as we get older – particularly if we give them plenty of exercise. “Over time, and especially with challenge, brain cells sprout new projections called dendrites,” says Dr. Gene Cohen, author of “The Creative Age” and director of the Center on Aging, Health and Humanities at George Washington University. Dendrites flourish in the brain’s critical information-processing sector throughout our 50s, 60s and 70s.

　　Despite the gain in dendrites, mental processes tend to lag. “Your reaction time slows down with age,” says Dean Keith Simonton, a psychology professor at the University of California, Davis. “Forget it if you want to take up tennis in your 50s and become a world-class player. But creating things is not a speed test.” Still, some mental pursuits do make it easier than others for young minds to excel. “Different fields require different amounts of expertise,” says Simonton. “In fields that are very abstract and very finite, like higher mathematics, you can make a contribution earlier.”

　　For those who like scientific definitions, creativity is an exasperatingly slippery concept. Scheibel explains the process as “the putting together of familiar information in an unusual way.” Nevertheless, the seemingly simple idea covers a range of mental tasks, all of them valuable. Researchers sometimes measure creativity by seeing how many different ways a subject can devise to use a paper clip, say, or a toothpick. “If you look at people’s performance on those tests, it tends to increase until around 40 years old, and then it starts to decline,” says Simonton. “But if you look at something called practical creativity – solving everyday problems you have in life – that peaks later.” Sometimes much later, as in the case of Ben Franklin, who at 78 invented the world’s first bifocals for himself.