At five foot six and 270 pounds, the bank robber was impossible to miss. On April 19, 1995, he hit two Pittsburgh banks in broad daylight. Security cameras picked up good images of his face — he wore no mask — and showed him holding a gun to the teller. Police made sure the footage was broadcast on the local eleven o’clock news. A tip came in within minutes, and just after midnight, the police were knocking on the suspect’s door in McKeesport. Identified as McArthur Wheeler, he was incredulous. “But I wore the juice,” he said.
Wheeler told police he rubbed lemon juice on his face to make it invisible to security cameras. Detectives concluded he was not delusional, not on drugs — just incredibly mistaken.
Wheeler knew that lemon juice is used as an invisible ink. Logically, then, lemon juice would make his face invisible to cameras. He tested this out before the heists, putting juice on his face and snapping a selfie with a Polaroid camera. There was no face in the photo! (Police never figured that out. Most likely Wheeler was no more competent as a photographer than he was as a bank robber.) Wheeler reported one problem with his scheme. The lemon juice stung his eyes so badly that he could barely see.
Wheeler went to jail and into the annals of the world’s dumb- est criminals. It was such a feature, in the 1996 World Almanac, that brought Wheeler’s story to the attention of David Dunning, a Cornell psychology professor. He saw in this tale of dim-witted woe something universal. Those most lacking in knowledge and skills are least able to appreciate that lack. This observation would eventually become known as the Dunning-Kruger effect.
Dunning and a graduate student, Justin Kruger, embarked on a series of experiments testing this premise. They quizzed undergraduate psychology students on grammar, logic, and jokes, then asked the students to estimate their scores and also estimate how well they did relative to others (on a percentile basis). The students who scored lowest had greatly exaggerated notions of how well they did. Dunning had expected that, but not the magnitude of the effect. His first reaction to the results was “Wow.” Those who scored near the bottom estimated that their skills were superior to two-thirds of the other students.
Those who scored higher had, as might be expected, more accurate perceptions of their abilities. But (are you ready for this?) the group that scored highest slightly underestimated their performance relative to others.
As the researchers observed, the only way to know how well you did on a grammar quiz is to know grammar. Those lacking that knowledge were also least able to gauge their knowledge. They were oblivious to their own ignorance.
Everyone thinks he or she knows what’s funny. The joke test included these two examples:
- Question: What is as big as a man but weighs nothing? Answer: His shadow.
- If a kid asks where rain comes from, I think a cute thing to tell him is, “God is crying.” And if he asks why God is crying, another cute thing to tell him is, “Probably because of something you did.”
The goal was to rate the funniness of each joke. Dunning and Kruger had a panel of professional comedians rate the jokes, and their averaged opinions were then considered “correct.” The comedians judged the first joke as not funny at all, while the second (written by Saturday Night Live writer Jack Handey) was rated very funny. Some quiz takers struggled to make that kind of distinction — yet were confident of their ability to determine what’s funny.
Later research went far beyond the university. For one experiment Dunning and Kruger recruited gun hobbyists at a trapshooting and skeet-shooting competition. Volunteers took a ten-question gun safety and knowledge quiz adapted from one published by the National Rifle Association. Again, the gun owners who knew the least about firearm safety wildly overestimated their knowledge.
Like most rules, this one has exceptions. “One need not look far,” Dunning and Kruger wrote, “to find individuals with an impressive understanding of the strategies and techniques of basketball, for instance, yet who could not ‘dunk’ to save their lives. (These people are called coaches.)” But of course coaches understand their own physical limitations. Similarly, “most people have no trouble identifying their inability to translate Slovenian proverbs, reconstruct a V-8 engine, or diag- nose acute disseminated encephalomyelitis.”
The Dunning-Kruger effect requires a minimal degree of knowledge and experience in the area about which you are ignorant (and ignorant of your ignorance). Drivers, as a group, are subject to the effect—bad drivers usually think they’re good drivers — but those who have never learned how to drive are exempt.
Since Dunning and Kruger first published their results in the 1999 paper “Unskilled and Unaware of It: How Difficulties in Recognizing One’s Own Incompetence Lead to Inflated Self-Assessments,” the effect named for them has become a meme. It strikes a universal chord: as Dunning put it, the over- confident airhead “is someone we’ve all met.” The Ig Nobel Prize committee awarded the duo one of its satirical prizes in 2000. Actor John Cleese concisely explains the Dunning-Kruger effect in a much-shared YouTube video: “If you’re very, very stupid, how can you possibly realize that you’re very, very stupid? You’d have to be relatively intelligent to realize how stupid you are....And this explains not just Hollywood but almost the entirety of Fox News.” The Dunning-Kruger effect is now part of the vocabulary of Internet snark (and some who think they know what it means don’t quite get it). But the 1999 paper makes clear the authors’ opinion that the first place to look for a Dunning-Kruger ignoramus is in the mirror.
Excerpted from Head in the Cloud by William Poundstone.
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