What does a failed bank robbery have to do with one of the most cited ideas in psychology?
More than you might expect.
In this episode of My Favorite Mistake, Mark Graban tells the true story of McArthur Wheeler, a man who believed that rubbing lemon juice on his face would make him invisible to security cameras. Confident in his reasoning—and even more confident in his ability to test it—Wheeler walked into two Pittsburgh banks in broad daylight, fully exposed, certain that his citrus-based logic would protect him.
It didn’t.
When police later showed him clear surveillance photos, Wheeler’s stunned response became legendary: “But I wore the juice.”
That moment caught the attention of psychologist David Dunning, who saw in Wheeler’s mistake something deeper than criminal incompetence. Along with Justin Kruger, Dunning went on to study how people with low skill often lack the awareness to recognize their own limitations—research that became known as the Dunning–Kruger Effect.
This episode explores the layered nature of mistakes: flawed assumptions, poorly designed tests, and the dangerous certainty that both are correct. It’s not a story about stupidity. It’s a story about human blind spots—and how easily confidence can outrun competence.
Whether in leadership, work, or everyday life, the lesson is universal: it’s not enough to test our ideas. We also have to test how we test them.
Because some of the most convincing mistakes are the ones that feel like proof.