Ever wonder why some people sound so confident—yet are completely wrong?
David Dunning got an idea in the late 1990s after reading about a man named McArthur Wheeler.
- Wheeler robbed two banks in Pittsburgh in 1995. He rubbed lemon juice on his face, thinking it would make him invisible to security cameras (since lemon juice can be used as invisible ink). Of course, he was caught almost immediately.
Dunning was fascinated. He wondered: How could someone could be so wrong and yet so confident? That led him (and graduate student Justin Kruger) to run a series of experiments where people took tests in grammar, logic, and humor, then estimated how well they had done.
- The people who scored the lowest consistently overestimated their performance.
- The people who scored the highest tended to underestimate themselves.
That was the birth of the Dunning–Kruger effect (published in 1999).
Why do some people sound so sure, even when they’re wrong?
- People who know a little often think they know a lot.
- People who know a lot often think they don’t know enough.
That’s why someone like RFK Jr. can speak with such confidence about vaccines and science—yet be dangerously misinformed.
Next time someone seems over-confident, it might just be this bias at work!
Progressive Teachers Network 
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