Many of us believe our folk theories about people are not just true, but scientifically backed.

We overestimate how well we understand minds—until we are asked to actually explain them.

Real expertise brings humility: the more we learn about the mind, the more we see what we don't know.

I have spent more than three decades studying, teaching, researching, mentoring, and practicing psychology. One phrase has followed me everywhere—dinner parties, clinics, classrooms, even the grocery store:

"You're a psychologist. You know..."

What comes next is always interesting. It is rarely psychology. Sometimes it is folk wisdom; sometimes a stereotype dressed as insight; sometimes—the part that fascinates me most—something scientific psychology rejected decades ago. It is said with complete confidence, as though my decades of study had merely been catching up to what everyone already knows. And the phrase contains a quiet trap: Because psychology itself has been enlisted as their witness, disagreeing with them doesn't sound like expertise but like disagreeing with science. There is a paradox folded inside it, too: The phrase recognizes expertise in the very act of erasing it. My colleagues report the same experience.

Now, before this sounds like a complaint, an admission: I do exactly the same thing. I have confidently explained inflation to economists and nutrition to physicians. This is not a story about annoying laypeople. It is a story about a cognitive illusion all of us share—one my field simply makes visible to me.

The Illusion of Knowing

The phrase troubles me not because people are wrong—being wrong is universal—but because of the claim hidden inside it. The speaker is asserting that their intuition is what the science says; that what they absorbed from culture, upbringing, social media, and movies is equivalent to knowledge developed through systematic observation, measurement,........

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