The Dunning-Kruger Effect

Say you’re walking around at a conference and someone stops you and asks,

“How good are you at what you do? How much do you know about your area of expertise? How confident are you in the decisions you take?”

How would you respond? Most people with only a slight hesitation will confidently rate themselves “above average,” in the 50th percentile or greater, relative to their mostly unfamiliar peers. Extended to a wider population this survey would produce an interesting result: a statistical impossibility, implying that many of us are uninformed about the limits of our knowledge and abilities. Why?

David Dunning and Justin Kruger, researchers at Cornell University, thought about this very same question and ran a series of experiments to determine how individuals assess their individual and relative levels of competence. Their experiments uncovered a couple of interesting findings. First, that most of us are terrible at self-evaluation; there’s always a difference between self-assessed and actual levels of competence. And second, more importantly, that those who were least skilled overestimated themselves the most, forming in their minds the “mistaken impression that they were doing fine” – what we now call the Dunning-Kruger effect, summarized in the original research paper as:

“People tend to hold overly favorable views of their abilities in many social and intellectual domains…[T]his overestimation occurs, in part, because people who are unskilled in these domains suffer a dual burden: Not only do these people reach erroneous conclusions and make unfortunate choices, but their incompetence robs them of the metacognitive ability to realize it.”

The heart of the issue lies in our inability to recognize the boundaries of our competence. The line between ignorance and knowledge is a fuzzy one, at best, and we move between these regions effortlessly and always unaware. While such lapses are more readily observed in those with less experience and competence, everyone, including experts, is susceptible to it. A brief survey of the history of mankind reveals numerous instances of highly regarded ideas, held by esteemed experts, that were later shown to be severely deficient, or outright falsehood: the flat earth theory, Ptolemy’s idea of the geocentric universe, Aristotle’s assertions on falling objects[1]. And there’s no reason to believe that this trend will stop – many of the ideas we hold dear will fall by the wayside in due time.

“The line between ignorance and knowledge is a fuzzy one, at best, and we move between these regions effortlessly and always unaware.

The challenge, then, is to develop mechanisms to spot and avoid or prevent these failings. This is easier in some areas of life more than others. Most workplaces, for example, have systems that allow employees to track their progress relative to their peers and responsibilities. But other, arguably more important areas of life – relationships, leadership, parenting – have no objective metrics and we resort to crude, flawed self-assessments when seeking improvement. This can have serious implications on how we go about our lives. Someone comfortable with their ignorance will not seek improvement, in the long run losing out on many things that life has to offer. At the other end of the spectrum, a competent person not realizing their true capacity could limit himself and avoid taking on greater challenges.

Dunning and Kruger’s experiments identified a couple of strategies that can help: training and feedback. Their experiment revealed that even modest levels of relevant training (in the paper it was 10 minutes) improved participants’ “metacognition” – the ability to understand one’s own thought processes – to a sufficient level that cured them of the delusions they had about their abilities and allowed  them to make more reasonable reassessments of their skill level – an essential first step for those seeking improvement.

Feedback, the honest kind, is another useful tool. Behind every home cook who enrolls to become a chef, “liked” photographer who goes pro, and not-so-funny comedian standing on stage is a white lie they received from a friend or family member when they sought feedback; well-intentioned, but ultimately counterproductive. To be of any use, you must seek feedback only from those with relevant expertise. And of course, be willing to consider the feedback you received.

Interested in learning more about the Dunning-Kruger effect? Check out the original research paper and listen to Professor David Dunning on the You’re Not So Smart Podcast.


 [1] In 340 BCE, Aristotle asserted that objects fall at a rate proportional to their weight. People accepted this for two reasons:
  1. it sounded reasonable
  2. Aristotle said it.
A combination of reasonableness and appeal to authority perpetuated this error for centuries. This was finally disproved in the 16th and 17th century by Galileo when people moved away from authority to evidence-based problems.