Ever wish you could read your customer's mind? Gerald Zaltman, a marketing professor at the Harvard Business School, uses brain scans, psychotherapy-like interviews, and his patented Zaltman Metaphor Elicitation Technique (ZMET) to help the likes of Procter & Gamble, Pfizer, General Motors, and Coca-Cola get inside the consumer's head. Author of the forthcoming How Customers Think (Harvard Business School Press, January 2003), Zaltman spoke to us about metaphor, Vanilla Coke, and triggering disgust.

Q: What's wrong with focus groups?
A: At least 95% of the thinking that drives our behavior occurs unconsciously--much of what we think of as conscious will is an after-the-fact construction. So people are often buying products for reasons they're not fully aware of.

Q: So buying motor oil might actually be my way of saying, "I love you." How do you figure that out?
A: You need to engage other languages of the mind. Every metaphor reveals lots of hidden knowledge. So for a recent study we asked people to bring eight-by-ten pictures that represented their thoughts and feelings about snack foods. For example, one person showed up with a picture of someone covered with bees. Then a trained interviewer asks them to use the pictures to tell a story, while a specialist in digital imaging helps them form the images into a collage. You're able to get a very robust set of insights.

Q: What was the bee picture all about?
A: That person had a lot of confidence that she wouldn't get stung--that she could safely indulge in snack foods without running the risks of harm that everyone else talks about. So there was a bit of defiance to it.

Q: So what do the brain scans do?
A: We call it "interviewing the brain." By monitoring the blood flows in the brain and seeing cortices light up, you're able to draw certain inferences: whether a [new-product] stimulus is being experienced in a negative or positive way; whether people are able to visualize it; whether areas of the brain involved in memory retrieval are active. We're close to having some new technology. It's kind of like a cap you put on people.

Q: Did Coke try any of your techniques before it launched Vanilla Coke?
A: No.

Q: Because I have a very vivid association with that product.
A: What is your association?

Q: Puke.
A: Actually, you're addressing an interesting area. We study joy and happiness but never disgust--and yet it's the foundation for so many industries: cosmetics, personal appearance, the whole industry of being clean. If you want to know what attracts consumers, you have to know what repels them. Because you don't want to inadvertently trigger it.