When You Don't Know...

Remember that trick about invisible ink from your school days? If you wrote a message with lime juice on a piece of paper, and let it dry, it would be invisible. And then if you held a candle up to it, the heat would reveal the secret message. Remember that?

Well, it was a trick that fascinated McArthur Wheeler. A man you’ve probably never heard of. But there’s a lesson he can teach us all. About ourselves.

McArthur had an idea. Since lime juice had the property of making things invisible, he reckoned he could put it to good use. He decided to rob a bank. And to make sure he would remain invisible; he smeared a lot of lime juice on his face. He even took a polaroid ‘selfie’ – which apparently threw up a blank image. Emboldened by his genius idea, he stepped out one fine morning in Pittsburgh and robbed not one but two banks. Of course, he was fully prepared. A Gun in one hand. And lots of lime juice on his face.

As the police looked at the bank’s CCTV camera footage, they could clearly see the face of the robber. He even seemed to be smiling into the camera. The cops put the footage out on the evening news on television, asking for leads if anyone could recognize the robber. And soon enough the cops were led to McArthur’s home.

When they told him he was being arrested for the bank robberies, he could hardly believe it. “But I wore the juice!” is what he apparently told the police. Medical tests confirmed he was not on drugs. He wasn’t delusional. He was just super-confident he had a fail-safe plan.

When David Dunning – a professor of Psychology at Cornell University and Justin Kruger (then a Ph D student at Cornell) heard Wheeler’s story, it led them to an underlying human trait. What’s now known as the Dunning – Kruger effect. It’s a cognitive bias: people of low ability or knowledge in a particular area tend to over-estimate their skill and ability in that area. When you don’t know, you tend to not know that you don’t know.

And what about the blank polaroid image? Well, he probably just got that wrong too. But since it confirmed his beliefs, he quickly concluded all was well. Like we all do.

Ah, the Dunning-Kruger effect. It’s all around us. And it’s good to know that it affects us all.

And if you are looking for examples, you can probably think of bad drivers (who all they think they are very good!). Or that poor performer at work (who is convinced he is a star – but it’s just that the boss doesn’t like him).

But here’s what Dunning and Kruger have to say: if you are looking for an example of the Dunning-Kruger effect, the first place you must look at is a mirror.