People lie. What we want isn’t always what we say we want. This poses a problem for marketers, who depend on market research before launching new or redesigned products. Researchers have learned that people in focus groups tend to tell the authority figures running the test what they think the tester wants to hear. They say that they’re interested in products without considering whether they would actually buy them. They say that something draws their eye when it really doesn’t. Fortunately, technology has caught up with our lies. Market researchers can now track subjects’ retinas to see what products really draw their eye, analyze barely perceptible involuntary facial expressions, and even monitor brain waves to see which choices elicit happy thoughts.