Robert Cialdini, 64, until recently a psychology and marketing professor at Arizona State University, wrote Influence, the classic book on persuasion. Lately he’s been researching the best ways to persuade people to save energy. In 2007, he coauthored a study [PDF] that found that giving people info about neighborhood energy-use norms (combined with smiley faces) led to large home energy savings. His research inspired the creation of the company Opower, which sells software that utilities can use to make smarter bills and inspire energy efficiency. Cialdini now serves as chief scientist for Opower and is president of the Influence at Work consulting firm. Read a Grist interview with Cialdini and Grist article about Cialdini’s work and Opower.