Brain-improving games have mostly been debunked. But there's still one that may be worth a try.

Can playing an online game make your brain work better? Earlier this year, the maker of the Lumosity app, which widely advertised cognitive and memory benefits from playing its games, was fined $2 million by the Federal Trade Commission for making deceptive claims. Does that mean you should abandon the idea that playing an online game could ever make you smarter? Not necessarily.

Although most online games only improve your ability to play the games themselves, there's one brain-straining type of game called "dual n-back" that may actually improve your cognitive ability. Dual n-back games are in widespread clinical use both for testing and for treatment of ADHD and traumatic brain injury. Research suggests that not only do they provide at least temporary improvement in these conditions, they also improve fluid intelligence--the ability to solve unfamiliar problems--in healthy brains, raising them the equivalent of 3 to 4 IQ points. And they may also improve working memory, which is the mental clipboard that stores information in the short term until it's needed, thus allowing you to construct complex ideas or solve multi-faceted problems.

So what exactly do these powerful games consist of? An n-back game asks you to press a button or otherwise respond when a letter, image, or other information is repeated within a sequence. "N-back" refers to how far back in the sequence it first occurred. For example, in the sequence A B B C, the repeated B is 1-back. In the sequence A B C B, the repeated B is 2-back. In A B C C B, it's 3-back, and so on. You have to identify when a letter is repeated first as a 1-back, then a 2-back, then a 3-back, and more, forcing you to keep more information in your short-term memory at each level.

In a dual n-back game, you have to play two n-back games at once. In one widely available version, you hear a sequence of letters and have to press one computer key when you hear one repeated in the correct n-number in the sequence. You have a second n-back task to perform simultaneously, pressing a different key when a blue block occupies a repeated square within a tic-tac-toe board.

Needless to say, this is really hard to do. (You can try it for yourself here.) It's considerably less fun than, say, Candy Crush. If you're someone like me who likes to thoroughly master one skill level before moving on to the next, it might be especially frustrating because the game encourages you to keep pushing to more difficult levels even if you didn't get the last level right. Not only that, the research seems to suggest that to continue reaping the benefits, you have to keep playing the game on a regular basis.

Even so, it's worth giving this ultra-challenging game a try. For one thing, it's available free. It's a small time commitment to try it out. And, in addition to at least some research that shows definite benefits, many people who play the game report cognitive improvement and even better performance on academic tests. Sure, that might be the placebo effect at work--but anything that makes you believe you're smarter will tend to actually make you smarter. And isn't that what you wanted all along?