January 18, 2010
Bonnie Rochman

Last Spring, as Arthur Marquis started brushing up on the French he’d learned in junior high, the 61-year-old retired lawyer and Long Beach, Calif., resident had trouble discerning where one mellifluous word ended and the next began. So he decided to exercise his auditory skills in much the same way a bodybuilder might zero in on a particular muscle group. His weapon of choice: Posit Science’s Brain Fitness software, which promised to hone his hearing, as well as his memory, for $395. (Yes, you heard that right: $395.) After completing the program’s 40 hour-long sessions, he’s a believer. “Now I can distinguish the words and hear better,” says Marquis. “It’s not cheap, but I never felt, Oh, man, I wasted my money.” (See the top 10 video games of 2009.)

When it comes to mental acuity, there is plenty of research to support changing your diet (fish, for example, is fab for your noggin), reducing stress and staying both socially engaged and physically fit. Scientists also know that it’s good to give the brain a workout. Studies show that software can improve targeted brain operations like focusing, attention and peripheral vision. But what researchers don’t know is whether pricey computer programs work better than an old-fashioned crossword puzzle.

That lack of conclusive data hasn’t deterred the nascent neurobics market. Sales are expected to jump from $265 million to up to $5 billion by 2015, according to a May report from market-research firm SharpBrains, which will sponsor the industry’s first conference, set to begin Jan. 18. (Watch TIME’s video about exercising with a hula hoop.)

Memory-enhancing offerings range from Dakim’s $2,300 touchscreen cognitive-fitness machine, used in more than 300 senior-living facilities in the U.S., to Nintendo’s $20 Brain Age, whose two versions have been purchased by millions of gamers looking to do such things as play sudoku or simultaneously count people entering and leaving a house. Allstate launched a pilot program in 2008 that gave 100,000 customers software designed to improve their reaction time behind the wheel. And American Airlines offered a free memory game in an online promo in December.

With a host of companies trying to tap into baby boomers’ fear of senior moments, the growth in cognitive-fitness products has as much to do with aging consumers as it does with the discovery that adult brains can generate new cells. At least six weeks of sustained, intense learning generally results in increased brain thickness. This finding has fueled a hot theory in Alzheimer’s research: the more you work out your brain, the more you accumulate what is referred to as cognitive reserve. (See more about the brain.)

This extra brainpower can help an aging mind compensate and, in essence, delay the onset of dementia. “The longer you put it off, the less time people will suffer from it,” says Yaakov Stern, a Columbia University cognitive psychologist, who has found that people with more education and more stimulating jobs are at a lower risk for developing Alzheimer’s.

But will a few minutes of solving brainteasers each day add up to much of anything? In a study published in April in the Journal of the American Geriatrics Society, scientists at the Mayo Clinic and the University of Southern California used standardized memory tests to assess 487 healthy adults over the age of 65, half of whom were asked to complete Posit’s two-month brain-fitness program. The results of the Posit-funded study show that the software users improved their mental speed by about 60% compared with 7% in the control group.

Afterward, nearly half of the Posit users noted improvements in everyday situations like remembering names or following conversations in a noisy restaurant, but so did 40% of the control group—and all they had to do during the study was watch the History Channel and get quizzed on it.

So what should we make of this? For starters, self-reporting is not a reliable way to assess how well our brains are working. And slick marketing makes it hard to tell what’s good from what’s gimmicky. “There is not enough evidence that paying for a $100 fitness program gets you better results than a free game of chess or learning a new card game or bridge strategy, when it comes to improving your memory,” says P. Murali Doraiswamy, a professor of psychiatry and geriatrics at Duke University and head of the school’s new mental-fitness lab. (See 10 myths about dieting.)

Doraiswamy is intrigued by many of the new brain-training products but dismayed by the lack of research on their effectiveness. “Manufacturers are putting the cart before the horse,” he says. Ultimately, he wants his lab to be a testing ground for claims of enhanced cognition, a kind of Consumer Reports for brain-fitness products.

One well-documented way to slow memory decline is through plain old aerobic exercise, says Art Kramer, a cognitive neuroscientist at the University of Illinois, who found that six months of walking for about an hour three times a week improved memory, attention and decision making among study participants, whose average age was 72. “Physical activity appears to be neuroprotective,” Kramer says. (See TIME’s video about fitness gadgets.)

That helps explain why some consumers are hedging their bets by hopping on a NeuroActive Brain Bike. The $4,000 machine debuted a year ago at Lady of America fitness centers, where members—who tend to be older than the average gym rat—quickly fell for the cardio-cognitive combo. “Instead of mindlessly watching TV” while pedaling, says Gerry Weber, CEO of Lady of America, which has 300 women’s-fitness franchises worldwide, “they’re able to exercise their brain at the same time.”

Perhaps what’s most important to remember amid the thicket of memory games, iPhone apps and other newfangled gadgetry is to just do something—preferably something novel—that engages your brain. Oh, and make sure you enjoy it too. “If you hate going to the gym,” notes Bill Thies, chief medical officer for the Alzheimer’s Association, “you’re not going to go there on a regular basis.”

Neurobic Activity: What’s good and what’s gimmicky

NeuroActive bike
It’s well documented that exercise slows memory decline, so users will benefit from pedaling on this $4,000 bike. What’s less clear is the effectiveness of the memory games, which riders play via wireless mouse

InSight Software
Posit Science’s $395 program is designed to aid memory and speed up thinking. But only one InSight exercise has undergone extensive independent testing, which showed it improves driving safety

Brain Age Games
Patients at Duke’s mental-fitness lab give high marks to these $20 game sets for Nintendo DS but find their improvement quickly plateaus in such activities as unscrambling letters or counting currency

Sudoku Puzzles
All you need to solve these number games is logic and a pencil. But since brain training requires both persistence and novelty, be sure to keep at it and also vary your regimen