The Dunning-Kruger Effect

What links an inept bank robber, Charles Darwin and two Cornell University psychologists? Read on to find out!

David Dunning and Justin Kruger describe the Dunning-Kruger effect as a cognitive bias of both unskilled and highly skilled individuals. What I find most interesting is the differentiation between how the bias affects the skilled versus the unskilled.

  • Those that are relatively unskilled are biased towards thinking that they are better at a task than they actually are.
  • Whereas highly skilled individuals underestimate their competencies, instead thinking that a task that they find easy will be easy for everyone, regardless of how objectively difficult it might be.

This is aptly summed up in the statement below:

“The miscalibration of the incompetent stems from an error about the self, whereas the miscalibration of the highly competent stems from an error about others”

(Kruger and Dunning, 1999)

This topic is such a huge source of fascination to me. One reason in particular is that it is by no means a new phenomenon. Although given its Dunning-Kruger moniker in only 1999, scientists have been aware of it well before. For example the extraordinarily talented Charles Darwin commented in the Descent of Man that

“Ignorance more frequently begets confidence than does knowledge”

(Darwin, 1871)

This covers precisely the bias of unskilled individuals; they think they know something exactly because they do not know it well enough (feel free to swap know for understand  or vice versa at any point in this post, depending on what side of that particular precipice you stand). Darwin goes on to say

“It is those who know little…who positively assert that this or that problem will never be solved”

(Darwin, 1871)

Or, less eloquently put, individuals without the skills to understand an issue will often by the first to say it is intractable. Even more interestingly we are all prone to some degree of agnosognia, or deficit of self-awareness, about ourselves. If you are not very good at something then often it can be impossible to know you are not very good at it!

“The skills you need to produce a right answer are exactly the skills you need to recognize what a right answer is”

(Morris, 2010)

From a personal perspective there are obvious exceptions that come to my mind; I know I am not very good at singing or speaking Russian. There is no false sense of expertise in these fields! But my concern is the things that I think I am good at… Perhaps my confidence in thinking I am good at explaining the semi-conservative replication of DNA is totally misplaced? Perhaps it is a combination of the Dunning-Kruger effect twinned with “The Curse of Knowledge” (another closely linked cognitive bias, this time held by people who know a great deal on a subject and assume others know as much causing issues when they try to explain concepts)?

At times in my teaching career I have had the immodesty to think that I am good at helping students learn in general. Reverse Imposter Syndrome* might be the culprit?! I am an impostor thinking that I understand a topic, simply because I do not have the capability to realise I do not understand it. Or as Dunning put it perfectly:

“We are all just confident idiots”

(Dunning, 2014)

There have certainly been watershed moments in my time as a teacher. When looking back I have realised that certain techniques or strategies didn’t really work. Certainly reading literature on learning has allowed me to see how I can refine and improve my practice. With each epiphany helping to shed a little more of my Dunning-Kruger outlook with the realisation that I did not know enough or understand what I was trying to do to actually evaluate it properly. I might venture to suggest most teachers are subject to a little of the Dunning-Kruger effect at one time or another. We are all, and this is by no means a criticism, “confident idiots” some of the time. Conversely we also fit the bill as unconfident geniuses* at times too. 

What of the inept bank robber mentioned at the start? This is perhaps the reason I find the Dunning-Kruger effect so interesting! The story goes that a man named McArthur Wheeler inspired the eponymous psychologists. Perhaps recalling the childhood activity of using lemon juice as invisible ink, he rubbed it into his face then set off to rob two banks. To his astonishment he was arrested shortly afterwards, police simply watched the CCTV footage from each bank. The height of stupidity one might argue? Yet this was not a spur of the moment decision; Wheeler had planned this novel approach, testing the lemon juice’s effectiveness by taking a photograph. The fact that the Polaroid picture in question was empty should not surprise us, it is thought that the camera had not been set up to face him. Wheeler fitted the bill of an unskilled individual so well that he could not even take his own photograph correctly! Or in more blunt terms:

“Wheeler was too stupid to be a bank robber [so] perhaps he was also too stupid to know that he was too stupid to be a bank robber”

(Morris, 2010)

*Recently there have been suggestions that the Dunning-Kruger effect leads to Imposter Syndrome, suggesting that feelings of inadequacy are due to the skilled thinking what they do is easy, thus devaluing the skill. This is exactly the reverse of the “confident idiot”, e.g. the unconfident genius.


Darwin, Charles, 1871, “The Descent of Man, and Selection in Relation to Sex”, John Murray, Introduction, p3.

Dunning, David, 2014, “We Are All Confident Idiots”, Pacific Standard, Tuesday 27th October 2014.

Kruger, Justin; Dunning, David, 1999, “Unskilled and Unaware of It: How Difficulties in Recognizing One’s Own Incompetence Lead to Inflated Self-Assessments”, Journal of Personality and Social Psychology, vol. 77 (6), p1121–34

Morris, Errol, 2010, “The Anosognosic’s Dilemma: Something’s Wrong but You’ll Never Know What It Is (Part 1)”, New York Times, Sunday 20th June, 2010.


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