You see them, too: Studies that report on what researchers learned from people about what they like, what they trust, and how they live.

Take a 2012 Nielsen study that reported on consumer trust in social and mobile advertising. Based on survey responses, Nielsen reported that people then trusted on-line ads more than they had previously—and that they trusted traditional (print and broadcast) ads less.

Every time I see these studies, I roll my eyes. You can’t ask people to self-report. And if you do, you can’t trust what they tell you.

People lie.

Unconsciously and accidentally, people won’t give honest answers when asked about their preferences and actions. In truth, they don’t know what they like. They don’t know how they act.

Time and again, research finds that people underestimate their number of daily calories. Per numerous studies, people fail to accurately assess their amount or intensity of physical activity. We cannot imagine a single cinnamon roll packs half a day’s caloric needs. We think ourselves more—or even less—active than our lives actually allow.

With ideas, people rarely like something they haven’t seen before. They need to warm up to new concepts. Asking people whether they like something and making decisions based on their responses may lead you astray.

In marketing, “psychographics” describes people’s self-concepts—and recognizes that they may not behave accordingly. That guy who just tossed a plastic water bottle into the trash? He pays more for products described as “eco-friendly” because he believes himself environmentally conscientious. That woman who said she doesn't trust magazine ads? She just purchased a box of granola bars promoted in her favorite fitness magazine.

Smart people observe their fellow humans’ behavior—as the adage goes, “actions speak louder than words”—to determine what they really believe and how they truly act. Trickier, more time intensive, and more expensive? Yes.

But observation provides the only route to truth.

How closely do your self-concept and reality align?