The Dunning-Kruger effect: Why does anyone state an opinion without knowing anything


Original Article: Efecto Dunning-Kruger, o por qué la gente opina de todo sin tener ni idea  Jennifer Delgado Suárez

The Dunning-Kruger effect can be summarize as follows: the less we know, the more we think we know. It is a cognitive bias by which those on the lower end of skills, abilities or knowledge tend to overestimate those very same skills, abilities or knowledge. As a result, these individuals become ultracrepidarians: People who have the habit of giving opinions and advice on matters outside their knowledge believing that they know more than the rest.

The essence of the problem is that the victims of the Dunning-Kruger effect do not only give an opinion or a suggestion, but they also try to impose their ideas as if they were absolute truths, passing others off as incompetent. Evidently, it can be very hard to establish a conversation with them, as they tend to have very rigid ideas and inflexible mindsets.

The offender who tried to become invisible with lemon juice

During the mid-90s, something surprising happened in Pittburgh. A 44 years old man robbed two banks during the day, in plain day light and without any type of face covering that could protect his identity. Logically, his career in crime was quite short as he was duly arrested.

Upon being taking by the police, this man, McArthur Wheeler, confessed that he had applied lemon juice on his face because it would make him invisible to the cameras. His answer was, “I don’t understand, I was wearing lemon juice!”

Later it was revealed that Wheeler got the suggestion of using lemon juice from a couple of friends. He put the idea to a test by spreading lemon juice all over his face and then taking a selfie picture on a mirror. For some reason his face did not appear in it. It is possible that the camera was out of focus, or out of frame, but Wheeler took the results of that test as a proof of invisibility.

When David Dunning, Professor of Social Psychology at Cornell University, read about this case, he could not believe his eyes. He asked himself the following question: Is it possible that my incompetence stops me from appreciating my own incompetence?

Quickly and with diligence, he started working on this idea together with Justin Kruger, a friend and collaborator. They conducted a series of experiments with astonishing results.

The study that originated the Dunning-Kruger effect

In a series of four experiments, these psychologists tested the abilities of a number of participants on different areas including grammar, logical reasoning and humour. Then they asked the same participants to rate themselves in each of these areas.

They found that the most incompetent ones were less aware of their level. Paradoxically, those with highest levels of competence used to underestimate their value. This is how the Dunning-Kruger effect was born.

They also concluded that people who display high levels of incompetence within a field:

  • Are incapable to detect and acknowledge their incompetence
  • Do not acknowledge other people’s competence

The good news is that this effect weakens as people increase their level of competence and become more aware of their own limitations.

Why the less we know the more we think we know

The problem with this distortion of reality is that, in order to perform well in a particular task, we need to have a minimum level of knowledge and skills to be able to accurately predict how we will perform on that task.

For example, a person may think that is very good at singing because has neither knowledge of music nor of all the skills you need to learn to adequately modulate the tone of your voice with good rhythm. The person may state in public that “sings like angels” when in fact the voice is horrendous.

The same situation may take place with orthographical skills. If we do not know where the mistake is then we cannot correct it, as we will not be aware of our limitations.

Actually, the Dunning-Kruger effect can be applied to all areas in life. A research conducted at the University of Wellington revealed that 80% of drivers believe their skills are above average, something that it is statistically impossible for obvious reasons.

You can also appreciate this cognitive bias within the field of Psychology. You can find many individuals affirming that they are their “best Psychology Counsellor”, simply because they ignore the range of tools and services that this profession offers.

In practical terms, we tend to believe that we know everything that we need to know. This transforms us in biased entities with a tendency to block the update of new information and to freely offer our opinions as if they were absolute truths.

How to minimise the Dunning-Kruger effect for our own good

We all make errors due to our lack of advanced planning, thought or knowledge. History has been riddled with epic mistakes, as for example the leaning tower of Pisa, which started to lean even before finished. Even recently, the French government spent thousands of millions of euros in a brand new train fleet only to discover that their width was too large to fit in about 1,300 station platforms across the country.

In everyday life we can also commit mistakes due to our lack of experience or because we overestimate our capabilities. Mistakes are not intrinsically negative and we should not try to avoid them at all cost. Instead, we should turn them into learning tools, given that nobody enjoys the frustrating feeling of tripping over the same stone repeatedly.

In fact, we need to keep vigilant to this cognitive bias because our incompetence and lack of self-evaluation will not only take your to an incorrect assumption, but it will also encourage you to make future wrong decisions that can hurt you.

This means that, in some cases, our failures and errors in life may not be due to other people or our bad luck, but the direct consequence of our deficient self-evaluation.

To minimise the Dunning-Kruger effect, and not become that person who gives opinions on everything without knowing, it is important to apply the following rules:

  • Be aware, at least, of the existence of this cognitive bias.
  • Always leave space for doubt, for different ways of thinking and go about things in life.
  • Always give opinions from a position of respect for others. Irrespective of how sure you are about what you say, never try to impose your opinion on others.

You need to keep in mind that nobody is expert in all aspects of knowledge. We all have weak areas and ignore many facts. Because of this, it is best to face life challenges with humility and a learning attitude.

How to deal with people who do not acknowledge their incompetence or lack of knowledge

People with very strong opinions about everything lacking knowledge and undervaluing others normally make us very uncomfortable. Our first reaction will be to get irritated and angry. This reaction is perfectly normal, but it does not solve anything. We should learn to keep calm instead. Remember that only what you give power can affect you, only what you consider meaningful. Without any doubt, you should not place too much relevance on the opinion of someone who is not an expert and does not know about the topic.

If you don’t want the conversation to continue, simply say something like “I hear what you say. Thanks”, and leave it there. If you care for them and you would like set them free from this cognitive bias, then all you can do is to help them develop skills within this area.

Try to avoid using phrases such as: “you have no idea of what you are saying” because this way you will only make them feel attacked, prompting them to react in a defensive way without accepting suggestions. Try a new approach instead. You can say: “I have already listened to you. Now imagine for a second that things were not exactly like this”. The goal is to try to encourage an open mind attitude and see the problem from different perspectives.

You can also highlight that none of us are experts on everything, and we can even be profound ignorants. This is not necessarily negative, but a wonderful opportunity to keep on learning and grow as human beings.


Kruger, J. & Dunning, D (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; 77(6): 1121-1134.

McCormick, A. et. Al. (1986) Comparative perceptions of driver ability— A confirmation and expansión. Accident Analysis & Prevention; 18(3): 205-208.

Translate: Dra. Paloma Mari-Beffa (Senior Lecturer at Bangor University, Wales, UK)


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