Referent power—. If a person admires the qualities of a person or a group, he tries to imitate them by copying the referent’s behaviors (for example, choice of clothing, cars, and leisure activities). Prominent people in all walks of life can affect our consumption behaviors by virtue of product endorsements (50 Cent for Reebok), distinctive fashion statements (Fergie’s displays of high-end designer clothing), or championing causes (Lance Armstrong’s work for cancer). Referent power is important to many marketing strategies because consumers voluntarily modify what they do and buy to identify with a referent.

Information power—. A person can have power simply because she knows something others would like to know. Editors of trade publications such as Women’s Wear Daily often possess tremendous power because of their ability to compile and disseminate information that can make or break individual designers or companies.

Legitimate power—. Sometimes we grant power by virtue of social agreements, such as the authority we give to police officers, soldiers, and yes, sometimes even professors. The legitimate power that a uniform confers wields authority in consumer contexts, including teaching hospitals where medical students don white coats to enhance their standing with patients. Marketers may “borrow” this form of power to influence consumers. For example, an ad featuring a model wearing a white doctor’s coat can add an aura of legitimacy or authority to the presentation of the product. (“I’m not a doctor, but I play one on TV.”)

Expert power—. To attract the casual Internet user, U.S. Robotics signed up British physicist Stephen Hawking to endorse its modems. A company executive commented, “We wanted to generate trust. So we found visionaries who use U.S. Robotics technology, and we let them tell the consumer how it makes their lives more productive.” Hawking, who has Lou Gehrig’s disease and speaks via a synthesizer, said in one TV spot, “My body may be stuck in this chair, but with the Internet, my mind can go to the end of the universe.” Hawking’s expert power derives from the knowledge he possesses about a content area. This helps to explain the weight many of us assign to professional critics’ reviews of restaurants, books, movies, and cars—even though, with the advent of blogs and open-source references such as Wikipedia, it’s getting a lot harder to tell just who is really an expert!

Reward power—. A person or group with the means to provide positive reinforcement has reward power. The reward may be the tangible kind, such as what the contestants on Survivor experience when they get to stay on the island. Or it can be more intangible, such as the approval that the judges on American Idol (except Simon) deliver to contestants.

Coercive power—. We exert coercive power when we influence someone because of social or physical intimidation. A threat is often effective in the short term, but it doesn’t tend to stick because we usually revert back to our original behavior as soon as the bully leaves the scene. Fortunately, marketers rarely try to use this type of power—unless you count those annoying calls from telemarketers! However, we can see elements of this power base in fear appeals that some companies use to scare us into buying life insurance (“who knows when you might walk into a bus?”) as well as in intimidating salespeople who try to succeed with a “hard sell.”