In 1995, a man called McArthur Wheeler walked into two banks in Pittsburgh and robbed them in broad daylight

No mask. No disguise. Just lemon juice smeared across his face

Wheeler genuinely believed the lemon juice would make him invisible to security cameras, in the same way invisible ink works on paper

To reinforce his confidence, he even looked directly at the cameras and smiled

He was arrested within hours

When police showed him the footage, his response was one of total disbelief:
“But I wore the juice!”

That moment of stunned confusion didn’t just end a failed robbery

It sparked the research that would later become known as the Dunning–Kruger effect

Psychologists David Dunning and Justin Kruger weren’t interested in the crime itself

What fascinated them was Wheeler’s absolute certainty in something that was so clearly wrong

In 1999, they published their findings, describing a cognitive bias where people with limited knowledge or skill significantly overestimate their competence

At the same time, highly capable people often underestimate theirs

Wheeler’s lemon-juice logic has since become the textbook example

Not because it’s funny (although it is), but because it highlights something deeply human: ignorance doesn’t just leave gaps in knowledge, it fills those gaps with confidence

And this isn’t about bank robbers

We ran a workshop for a company the other week, and one attendee came up to me at the end and said:
“I thought I was really good on LinkedIn… until today. Now I need to think again.”

That comment comes up a lot

We regularly meet people who believe they’re social media experts

In reality, they haven’t even left the starting blocks

They’re posting, but not positioning

Active, but not effective

Busy, but not strategic

Conclusion

The real danger of the Dunning–Kruger effect isn’t that we don’t know enough

It’s that we don’t know what we don’t know

Growth starts the moment confidence is replaced with curiosity

When we stop assuming we’re invisible to the gaps in our own knowledge, and start learning how things actually work

Because lemon juice doesn’t make you invisible

And neither does confidence without competence