Everyone complains about "e-mail overload" – getting so much stupid corporate e-mail that you miss out on important messages. But Byron Reeves has figured out a way to solve the problem.

How? By turning corporate e-mail into a game.

Reeves, a communications professor at Stanford, had studied the spectacularly popular online game World of Warcraft, and he knew that people inside the game place enormous value on the game's artificial currency of gold pieces. They'll go on quests and spend hours doing boring tasks just to earn it. That gave him an idea: Why not create a system where users earn virtual currency by intelligently using e-mail?

So Reeves' firm, Seriosity, built a system – dubbed "Attent" – that does this. Every employee is given virtual tokens – say, 100 a week, – that they can attach to e-mail they write. If you really want someone to read a message now, you attach a lot of tokens, and the message pops up higher in your correspondent's Outlook inbox. Reeves figured this would encourage people to send less e-mail: Those who are parsimonious would wind up with lots of tokens, which means when they really have something to say, they can load it up with tokens and make sure it'll get through. Sure enough, that's what happened. When a work group at IBM tried out Attent, messages with 20 tokens attached were 52 percent more likely to be quickly opened than normal. E-mail overload ceased to be a problem.

"What we've proven is that games can change behavior," Reeves says.

We tend to think of videogames as frivolous activities – something we do to kill time, not to improve productivity. But a new generation of designers is taking a different tack: Like Reeves, they're using the principles of videogame design to transform everyday activities – helping people work more efficiently, use less energy, and get healthier. Turn the world into a game, they argue, and it works better. Give people a competition, and it can transform a dull-but-important task into something exciting.

"Games create drama and excitement," as Jane McGonigal, one of the leading thinkers in the field, told the crowd at this year's O'Reilly Emerging Technology Conference. "We've done that for years with videogames, and now we can apply that thinking to the rest of life."

Physical exercise is a leading example. One of Nike's latest successes has been the Nike Plus – a pedomoter that measures your footsteps as you walk and run, and reports them to your Apple iPod. Nike uses that information to build various game-like systems. If you break your distance record, for example, your iPod will play an audio clip of Lance Armstrong congratulating you – much as a videogame will offer a badge or "rare" reward for achieving a new personal best. Nike Plus users can also go online to a website where they can challenge friends – or even strangers around the world – to distance or speed competitions.

"It's exactly like a leaderboard in a game, where you want to have the bragging right of being on top, so you work harder at getting better," says Steffen Walz, a game theorist at the Swiss Federal Institute of Technology. Walz says governments worldwide are hiring designers to create games that encourage healthier behavior; he himself is creating one, where teenagers will run around their city with GPS-equipped mobile phones, unlocking prizes by visiting different locations.

"We're trying to get people to look at the whole city as a workout space," Walz says. "Obese kids are a big problem. They have unhappy lives, they have health problems, they cost a lot. So that's why you need a game to motivate them."

Games can change behavior by taking bad behaviors and making them visible, so we can no longer ignore them. For example, the onscreen dashboard in the Toyota Prius – a hybrid gas-electric car – shows drivers the gas mileage they're achieving, based on how wastefully or how efficiently they're driving. As many Prius owners have noted, this turns driving into a little competition, trying to achieve the highest mileage possible.

For his part, Reeves is working on a game to encourage people to use less electricity at home, by displaying their household's usage as an icon on a website, glowing green if it's using fairly low amounts of juice, and grey if it's wasting energy. Neighbors can sign up and see each other's usage, creating a competition to be the greenest household.

"Or imagine becoming the greenest house in your country," Reeves laughs.

In fact, games can be so addictive that it's like playing with fire: The trick is not to accidentally overmotivate users.

This spring, Dennis Crowley – a New York software entrepreneur – released "foursquare," a "location based" social-networking application that tracks any public place you visit (like a bar, restaurant or coffeehouse) and reports it to you friends. Crowley wanted to encourage people to go out a lot, so he added game-like elements: You get "points" for visiting multiple spots in one evening, for example, and badges for roaming far from home. Travel a lot and you'll be at the top of the weekly leaderboard, with hipster bragging rights. It worked – almost too well. Some people got so obsessed with racking up points that they began checking in dozens of times a day, frantically marking even a brief visit to Starbucks.

"We created a monster here," Crowley says ruefully, and he's reprogramming the game incentives to calm people down. Games are powerful; now it's up to designers to use them for good.