When Susan Stevens’ young son went into anaphylactic shock in 2006, she rushed him to the emergency room as her thoughts raced: Was it something he ate? Something he touched? Turns out a cashew caused the severe reaction, but she learned he had other severe allergies, leading her to completely reevaluate her family’s lifestyle choices. Stevens became adept at reading labels and selecting chemical-free cleaning products, and adopted other practices, such as removing shoes at the door to improve indoor air quality. She began blogging about her eco-friendly lifestyle, had her home renovated green and started night school for sustainable design. What started as a personal epiphany was becoming a passion to encourage sustainable behaviors in others. But how could she make a bigger difference?

In 2010, Stevens launched Practically Green, a business that uses game techniques to encourage people to complete simple actions as a path to collective environmental change. She was at the forefront of the emerging strategy called “gamification,” rooted in decades of social psychology research. Gamification uses games and social media to motivate behavioral change by tapping people’s instincts to follow social norms and to compete.In fact, marketing and business executives have used tools from social psychology to influence behavior for decades. In the 1990s, BJ Fogg pioneered the study of how technology can be used to influence behavior. His once-controversial research now garners millions of dollars for companies. “Persuading people through technology is the next social revolution,” Fogg, now director of the Persuasive Technology Lab at Stanford University, said in Fortune Magazine.

But can it be used to save the planet? Stevens thinks so.

Players compete for points and earn badges by completing suggested environmentally friendly actions in four categories: energy, water, health and “stuff.”

Before she started her business, Stevens had noticed how much time people spent on social media and on games like FarmVille and wondered, “What if people were doing things that matter?” But it wasn’t until she took a class on the U.S. Green Building Council’s LEED program, where buildings receive one of four levels of certification by earning points for various actions, that her pondering solidified into something concrete.

“I kept thinking, ‘Why isn’t there something like this for people?’” Stevens recalls. So she developed a point-based program modeled after LEED, but for daily life. Players compete for points and earn badges by completing suggested environmentally friendly actions in four categories: energy, water, health and “stuff.” Every action includes links to additional information, such as a database that contains details about various cosmetic products.

Stevens launched Practically Green at the inaugural SXSW Eco conference in Texas in October 2011. Just a year later, her clients include Seventh Generation, which uses the program to encourage employee sustainability, and NBC Universal, whose Practically Green–based app, “One Small Act,” is available from iTunes. Anyone can play Practically Green online at no cost—and tens of thousands do.

Keeping up With the Joneses

Although people often insist they are not influenced by others’ behavior, social scientists know better. In a well-known 2008 study, Arizona State University professor emeritus of psychology Robert Cialdini found hotel visitors were most likely to reuse towels when a placard stated that most of the occupants of a guest’s room reused their towels—even though each guest in a room has nothing in common with previous or future guests of that room. Messages listing the hotel average for towel reuse, or appealing to a sense of environmental stewardship worked less well in promoting towel reuse. Cialdini’s principle of influence, called “social proof”—what some think of as peer pressure or following norms—is central to gamification.

“When two, three, four, 10 people start to do [something], it starts to get all the people around them to do it, and then it goes over the tipping point and becomes the norm.” — Susan Stevens

“People tend to change over sustainability when the social norms change,” Stevens said at the “Why Should I?” panel discussion at the 2012 SXSW Eco conference. “When two, three, four, 10 people start to do [something], it starts to get all the people around them to do it, and then it goes over the tipping point and becomes the norm.” For people to act in a particular way—to recycle or carry a water bottle—the norm does not have to be across society, but can be within a company, neighborhood, school or group of friends. It can even involve a “granfalloon”-type group, such as residents of the same hotel room.