The Dunning-Kruger Effect: When incompetence begets confidence

Why dumb people are too dumb to understand exactly how dumb they are

By Anjana Nair

Artwork by William Hornbrook

27th July 2022

Meet Bob.

After a year of creating campaigns for an advertising company, Bob is convinced that his advertising skills are the best in the department. In his mind, his extraordinary and unique content guarantees a promotion. But when his manager releases the annual review, his face falls. “This is unbelievable”, Bob mutters. He bashes himself too hard, but still attests to the fact that he is the best in the department. 

What can you learn from his behaviour? First, don’t be Bob. Second, Bob’s case illustrates a psychological phenomenon called the ‘Dunning-Kruger effect’.

The Dunning-Kruger effect, a term coined by famous psychologists David Dunning and Justin Kruger in 1999, is a cognitive bias in which poor performers greatly overestimate their abilities. 

Dunning and Kruger’s research shows that underperforming individuals “reach erroneous conclusions and make unfortunate choices, but their incompetence robs them of the ability to realise it”. This incompetence, in turn, leads them to “hold inflated views of their performance and ability.” 

One of the reasons that the ignorant tend to be blissfully self-assured, as the researchers explain, is that the skills required for competence often are the same skills necessary to recognise competence. That is the biggest irony of all! The incompetent, therefore, suffer greatly. Put simply, Bob’s creative skills do need a lot of improvement. If Bob saw his deficiencies, he would be able to fix them, he wouldn’t fight constructive criticism of his campaign ideas, and frankly, he wouldn’t be so frustrating to deal with! Bob simply lacks this knowledge and intelligence and hence continues to remain ignorant of his skills. 

In a series of studies, Dunning and Kruger asked 65 participants to rate how funny different jokes were. Some of the participants were exceptionally poor at determining what other people would find funny, yet these same subjects described themselves as excellent judges of humour. 

Unlike their unskilled counterparts, the ablest subjects in the study were more likely to underestimate their own competence. The researchers attributed this to the fact that, in the absence of information about how others were doing, highly competent subjects assumed that others were performing as well as they were – a phenomenon psychologists term the “false consensus effect”. 

In another test, when high-scoring subjects were asked to grade the grammar tests of their peers, they quickly revised evaluations of their own performance. In contrast, the self-assessments of those who scored badly themselves were unaffected by the experience of grading others; some subjects even further inflated estimates of their own abilities.

This effect can have a profound impact on what people believe, the decisions they make, and the actions that they take. In another study, Dunning also found that women performed equally to men on a science quiz, and yet they underestimated their performance because they believed they had less scientific reasoning ability than men. The researchers found that, because of this belief, these women were more likely to refuse to enter a science competition. Researchers concluded that competent individuals often fail to recognise their capabilities.

So, what explains this psychological effect? Are some people simply ‘too dense’ to realise how dim-witted they really are? Dunning and Kruger suggest that this phenomenon stems from what they refer to as a “dual burden”. 

First, these deficits cause people to perform poorly in the domain in which they are incompetent. Secondly, their erroneous and deficient knowledge makes them unable to recognise their mistakes. Another contributing factor is that sometimes even a tiny bit of knowledge can lead people to mistakenly believe that they know all there is to know about it. As the old saying goes, a little knowledge is a dangerous thing.

Charles Darwin wrote in his book, The Descent of Man, “ignorance more frequently begets confidence than does knowledge.” This statement is completely contrary to what we believe or assume to be true – that the more knowledgeable we are, the more confident we will be. So, the real question here is simple – are you standing on the heights of stupidity, confidently and loudly declaring your knowledge and opinions as a rehab therapist? Because if you are, you are putting peoples’ lives and outcomes at risk. 

The other option is surely better. It is worth learning to recognise our own shortcomings, just as we are so frequently exhorted to recognise our strengths. After all, even Dr Dunning and Kruger presented their research with a degree of nervousness, and modesty when they said: 

“This article may contain faulty logic, methodological errors, or poor communication. Let us assure our readers that to the extent this article is imperfect, it is not a sin we have committed knowingly.”

Anjana Nair is Reviews Editor at I, Science and studies on the MSc Science Communication course here at Imperial. With her background in biotechnology, Anjana worked as a researcher and then pursued science journalism. In her free time, she loves to read science fiction and watch documentaries.