By your late 20s, you've already hit your mental peak and are giving up mental speed and efficiency, says Glenn Smith, a professor of psychology at the Mayo Clinic College of Medicine in Rochester, Minn.
That's not to say older brains don't have advantages. Experience, hard-won wisdom and guile can get a person far. But such reassurances aren't enough for millions of Americans in similar straits.
They've turned to "brain training" in an attempt to stop their mental decline. Such games and devices are specifically marketed as a way to keep brains sharp and youthful, working the gray matter with a variety of challenges -- word scrambles, timed math problems, memory games -- that take users beyond their usual thought processes.
Most users expect that working out the brain is a lot like working out the body: If they can get enough of the right kinds of exercise, they'll be mentally stronger and fitter as the years pass.
But the brain is much more complicated than muscle, and keeping it busy doesn't necessarily make it stronger, says Liz Zelinski, a professor of gerontology and psychology at USC.
According to Zelinski, a brain game or any other activity can't improve thinking or turn back the mental clock unless it's both challenging and novel enough to build new connections between brain cells. Crossword puzzles and sudoku can be fun, she says, but they mainly make use of old connections that people already have. The challenge for brain trainers is to go beyond typical games and brain teasers to give the brain the type of exercise it needs to really grow.
Brain-training products fall into three main categories: hand-held game devices, computer programs and Web-based exercises. The Healthy Skeptic checked out a prominent example of each type.
Brain Age 2, a game for the hand-held Nintendo DS, is one option for brain training on the go. (It's a popular option too. Nintendo says it has sold more than 17 million copies of the game and its predecessor, Brain Age, combined worldwide since 2005.) The game includes 15 activities that demand memory and fast thinking, including a challenging -- you could say flustering -- version of rock-paper-scissors that requires users to quickly choose the right weapon. The task is complicated by the fact that half the time the game asks users to lose.
Many tasks are completed by writing numbers or symbols on the screen with a stylus. A few others use voice recognition. (The next time you see someone shouting "paper" at a little gizmo, you'll know why.) Brain Age 2 costs about $25, and the DS itself costs about $130 to $170, depending on the model.
Then there's Lumosity, a subscription-based website developed by neuroscience researchers from Stanford University and UC San Francisco, offering dozens of activities that test problem solving, memory, speed, flexibility and attention. A "bird watching" game, for example, requires users to simultaneously track flashing letters and birds that can pop up anywhere on the screen, requiring quick attention to detail. (It's more fun than it sounds.)
Users can try a few games for free, but it takes a subscription to unlock the full site. A monthly subscription is $9.95. A year's access costs $79.95; lifetime access can be had for $339.
Brain Fitness, a computer program from Posit Science, is less like a game and more like a mental workout. The program offers six exercises that require users to listen carefully and think fast. In one exercise, users listen for a change of pitch in a short beep. In another, they have to notice and remember differences between very similar syllables. The exercises get progressively harder to keep up with a user's improving skills. The program, available in Mac and PC versions, is sold online for $395.
Brain-training games owe their existence to the premise "use it or lose it." In one way or another, they all claim to provide the kind of mental workouts needed to keep the brain sharp.
The Brain Age 2 tutorial claims that "you can train your brain just like you train your body." The game even includes pictures of brain scans showing the mind is much more active when doing math problems or word games than when thinking idly or watching TV. Nintendo doesn't come right out and say the game will make you smarter, but the website does claim the game will "stimulate the brain and give it the workout it needs."
The Lumosity website claims users can improve working memory and attention. It also says users have reported "increased alertness and energy, improved ability to remember names and numbers, better concentration and an elevated mood."
The website for Brain Fitness claims the program can help you "remember what you hear in any setting," "find words at the tip of your tongue" and "feel more alert and focused in conversations." It also says it can "improve memory by an average of 10 years."
Do brain games really work? Read more here: Brain-training games get mixed scores