The Dunning-Kruger Effect: How Does It Affect Us, And Does It Even Exist?


Dr. Katie Spalding

Katie has a PhD in maths, specializing in the intersection of dynamical systems and number theory.

Freelance Writer

shouting into megaphone

Everybody put down your vaccines and read this geocities website I found explaining how birds aren't real! Image Credit: ViDI Studio/Shutterstock

How good are you at spotting fake news?

What about politics – would you say you’re well-informed?


Have you “done your own research” on GM crops?

Well, we hate to break it to you (kidding! We love to break it to you) but you’re probably not as smart as you think. Don’t worry: it’s not just you. But what is it that so reliably blinds us to our weaknesses like this?

The answer may be something called the Dunning-Kruger effect.

What is the Dunning-Kruger effect?


On one day in 1995, a man by the name of McArthur Wheeler robbed two banks in Pittsburgh. Security camera footage hit the news that same day, and he was arrested just an hour later.

That surprised Wheeler. “But I wore the juice,” he complained when the police showed him the tapes.

Specifically, Wheeler had been “wearing” lemon juice. Reasoning that as the citrusy liquid can be used as invisible ink, he had figured that covering his face in lemon juice would render him invisible to the cameras.

To some, it was an amusing story of a foolish criminal getting his just desserts. But in the psychology department of Cornell University, David Dunning saw something else: a glimpse at a familiar and universal human foible. Together with his graduate student Justin Kruger, they conducted a set of experiments aimed at explaining the phenomenon. The resulting paper has since gone down in history – and so has the cognitive bias that now bears the pair’s names.


The Dunning-Kruger effect, simply put, is a cognitive bias that makes people think they’re good at a particular task – even though, in fact, they’re really bad at it.

“[P]eople who are unskilled in these domains suffer a dual burden,” explained the pair in the abstract of their 1999 paper, Unskilled and unaware of it: How difficulties in recognizing one's own incompetence lead to inflated self-assessments in the Journal of Personality and Social Psychology. “Not only do these people reach erroneous conclusions and make unfortunate choices, but their incompetence robs them of the metacognitive ability to realize it.”

So, for instance, that person online who keeps talking about how vaccines cause autism (they don’t, by the way) may honestly think they're better-informed than you – better informed than doctors and medical researchers, in fact. They honestly believe that – they just don’t have enough knowledge to realize how uninformed they truly are.

That’s the Dunning-Kruger effect.


What isn’t the Dunning-Kruger effect?

Ironically, many people who hold forth about the Dunning-Kruger effect (for instance, people on social media) have actually misunderstood it. It’s frequently used to call an online debate opponent “stupid” in a way that makes the insult sound somehow backed by science – but that’s not what the effect is about at all.

“The effect is about us, not them,” said Dunning in a conversation with Jonathan Jarry published by the McGill University Office for Science and Society. “The lesson of the effect was always about how we should be humble and cautious about ourselves.”

The Dunning-Kruger effect isn’t about being ignorant or having low intelligence, he explained: rather, it’s to do with being misinformed.


“If I am asked the boiling point of mercury, it is clear my brain does not hold the answer,” Jarry said to illustrate the point. “But if I am asked what is the capital of Scotland, I may think I know enough to say Glasgow, but it turns out it’s Edinburgh. That’s misinformation and it’s pushing down on that confidence button in my brain.”

Alternatively, consider the hundreds of people who got sick, went blind, or even died from taking bogus COVID-19 cures. They were, most likely, pretty normal people in many ways – but they had somehow been led to believe that salt water and methanol could treat their illness. Of course, it can’t – drinking even small amounts of methanol will kill you – but that simply wasn’t the information the hopeful patients were equipped with.

What are some real-world examples of the Dunning-Kruger effect?

The Dunning-Kruger effect has been demonstrated in a wide range of settings – and it seems nobody is immune.


“College students who hand in exams that will earn them Ds and Fs tend to think their efforts will be worthy of far higher grades; low-performing chess players, bridge players, and medical students, and elderly people applying for a renewed driver’s license, similarly overestimate their competence by a long shot,” Dunning wrote in Pacific Standard magazine in 2017.

Among the real-life consequences of his half-eponymous effect, he listed the 2008 financial meltdown – caused in part, he explained, by misled and ignorant consumers. One stark example he cited concerned financial literacy: research shows that while nearly three-quarters of Americans consider themselves financially savvy, in practice only seven percent can correctly answer questions on fundamental economic concepts such as mortgages and interest rates.

And the worse people are at managing their finances, the greater their belief in their own ability: “[Participants in a 2012 financial literacy study] who said they had filed bankruptcy within the previous two years performed fairly dismally on [a financial literacy] test – in the 37th percentile, on average,” he wrote. “But they rated their overall financial knowledge more, not less, positively than other respondents did [...] 23 percent of the recently bankrupted respondents gave themselves the highest possible self-rating; among the rest, only 13 percent did so.”

The reason? Pure Dunning-Kruger effect, he explained.


“Bankrupted respondents were particularly allergic to saying ‘I don’t know,’” he wrote. “Pointedly, when getting a question wrong, they were 67 percent more likely to endorse a falsehood than their peers were. Thus, with a head full of ‘knowledge,’ they considered their financial literacy to be just fine.”

The famous Dunning-Kruger "smirk" of experience vs confidence. Image source:AKLOKLOR/

But is the Dunning-Kruger effect real?

Despite its popularity in online flame wars, there’s a chance the Dunning-Kruger effect might all be in our heads. In the ultimate ironic twist, it turns out even Dunning and Kruger themselves may have been unaware of certain flaws in their thesis.

Two papers, published in 2016 and 2017 in the mathematics journal Numeracy, claimed to have reproduced the Dunning-Kruger effect using random data. And when writing for the McGill Office for Science and Society, Jonathan Jarry described yet another numerical experiment that confirmed the result.


What was going on? According to psychologist and statistics expert Patrick McKnight, the key lies in how the original data was presented. At first glance, Dunning and Kruger’s results look quite straightforward: their now-infamous graph plotted study participants’ perceived ability alongside their actual achievement. But look a little closer, and things aren’t quite as they seem – instead of measuring individual results, the participants have been split into quartiles. The graph actually plots the average actual score and average self-reported score in each quartile – and it looks strikingly similar to graphs obtained by plotting random data. What’s more, the supposed effect is amplified when less reliable data is used – which, McKnight explained, is a big statistical red flag.

“This graph, to my knowledge, is quite unusual for most areas of science,” he told Jarry. “We have no instance in the history of scientific discovery where a finding improves by increasing measurement error. None.”


So is the Dunning-Kruger effect really to blame for the downfall of modern society? Is it just a fancy name for foolishness? Or is it, paradoxically, simply a manifestation of the Dunning-Kruger effect? Statistical debunking notwithstanding, we don’t see the public love affair with Dunning and Kruger disappearing any time soon – so let’s just make sure we keep a sense of perspective.

“Because it’s so easy to judge the idiocy of others, it may be sorely tempting to think this doesn’t apply to you,” Dunning cautioned in 2017. “But the problem of unrecognized ignorance is one that visits us all.”




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