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Overconfidence: the Human Bias that’s Killing Your Investment Success

Overconfidence: the Human Bias that’s Killing Your Investment Success


Humans are astonishing creatures that are often astonishingly wrong about many things without even realizing it. Overconfidence is the human bias that causes investors a lot of losses, and we’re going to talk about it. Simply put: overconfidence the unfounded confidence one has in the abilities of themselves or that of others.

Johnny Bravo being overconfident

Overconfidence among investors is one of the major causes for investing failure

Thinking Fast and Slow

According to Daniel Kahneman, author of one of the best psychology books called ‘Thinking Fast and Slow’ and Nobel prize winner, overconfidence is particularly strong among investors. More than most other groups, investors tend to exaggerate their own skill and deny the role of chance. They overestimate their own knowledge, underestimate the risks involved

Daniel Kahneman Quote

Most people are confident, most of the time

Before you think ‘not me’..

Chances are that you read this and thought: ‘as if overconfidence affects me.. I’m a pretty down to earth man/woman’. However, Daniel Kahneman  showed a situation that was awkwardly recognisable.

Mr Kahneman conducted an experiment. In this experiemt he asked a large group of participants about their competence as automobile drivers in relation to the average driver. The results showed that 80 – 90% of the respondents invariably say that they are more skillful and safer drivers than others in the class. Almost all respondents consider themselves to be above average. That’s statistically impossible.

Illusory Superiority

A cartoon showing the concept of illusory superiority

Illusory superiority

Another way to describe overconfidence is illusory superiority. It’s one’s belief that they are better than average compared to other people in a given area of life. Be it looks, social skills or driving ability.

The phenomenon is very common and appears in all kinds of people. So common, in fact, that it comes up every time psychologists carry out experiments with it.

The Dunning-Kruger Effect

The Dunning-Kruger effect is what can be observed as a result of multiple people suffering from illusory superiority.

Dunning-Kruger graph

This graph shows that people with the least amount of experience tend to have extremely disproportionate levels of confidence in their ability. It is only when people become true experts in a certain field that they regain some of that confidence. The period in between is where people become painfully aware of how little they know and as a result their confidence drops.

Knowing Yourself

Many investors are convinced that they can beat the market because of overconfidence. It leads to them speculating more than they should and trading way too often. Knowing your human limits and acknowledging them as being REAL is how you begin overcoming overconfidence.

Acknowledging your weaknesses is a strength, whereas failing to do so makes for another weakness.

The Market is Rarely Beat

Studies have found that the more individual investors traded, the worse they did. It even turned out that male investors traded much more than women, with correspondingly poorer results. This is exactly the reason why I praise a ‘buy and hold’ strategy so much.

graph showing long-term growth

The Effects of Overconfidence

According to researchers, overconfidence in the ability to predict future growth leads to overvaluation. So called ‘growth stocks’ tend to be massively overvalued as a result of overconfidence in the ability to predict future growth. Additionally, exciting new technologies also affect the assessment abilities of investors. It leads them to expect nothing but success and project higher growth rates for the companies involved.

Therefore, the expectations regarding the earnings of these companies are extremely overestimated, with investors having more confidence than is justified. This leads to investors investing more and more money into stocks that they are overconfident about (The dotcom bubble of 2000 is a great example of this overconfidence).


Eventually, the financial laws of gravity will leave these investors with an empty wallet and a damaged ego.

Johnny Bravo suffering from overconfidence

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