The Overconfidence Bias

I would like to introduce the most common and dangerous thinking error: The Overconfidence Bias.

On August 29, 2011, the renowned National Taiwan University Hospital announced HIV-infected organs were mistakenly transplanted into five patients. How can this happen? The organs were not double-checked as required by standard procedures, all because of staffers’ overconfidence. Meanwhile, five patients must now take anti-AIDS drugs, and live in fear of an early death.

The severity of the consequences of the above mistake pale into insignificance when compared to the death toll, human suffering, and wasted government resources that resulted from the Vietnam War. America’s overconfidence in its ability to defeat a small Asian nation led to untold suffering in both countries.

What has the U.S. government learned about the dangers of overconfidence? Apparently not much. Here is Donald Rumsfeld commenting on the Iraq War, “The war… will last… six days, six weeks… I doubt six months.”

But this article is not about the U.S. It is about US and how overconfidence can lead US astray, create havoc, and ruin our lives. It does its dirty work in many ways. Consider the large number of divorces, broken homes, children torn apart from their parents. A spouse, who was once madly in love, may become complacent as time passes. Overconfident, they stop working on the relationship, and neglect or abuse their spouse until their marriage eventually explodes in their face.

In the workplace, because of their overconfidence, employees overestimate their ability to do a project and underestimate the time required to complete it. The result? Procrastination, sloppy work, stress and fatigue. And if these bad habits aren’t corrected, the employee may lose his or her job.

In everyday life we find people destroying their lives with drugs, alcohol, and gambling. Overconfidence in their ability to control themselves destroys them. For example, staggering out of a bar, and before driving away, a man tells his friends, “Oh, I’m okay. I can handle booze; I’ll get home safely.” But he never arrives home. Instead, his name is added to the list of highway fatalities.

People die in swimming, boating, and mountain climbing accidents because they overestimate their abilities and take irrational risks. Even the Bible cautions against overconfidence: “Let him that standeth take heed lest he fall.” (Corinthians 10:12) Overconfidence is a killer. Here’s another example. The last words of General John Sedgwick as he looked out over the parapet at enemy lines during the Battle of Spotsylvania Court House in 1864 were, “They couldn’t hit an elephant at this distance…”

I recently walked on the edge of an outdoor path that was 116 stories high. It is called Edge Walk and is one of the attractions of Toronto’s CN Tower. It was perfectly safe as I was strapped in a harness. However, a friend asked, “Isn’t it possible for the straps to come apart, causing you to fall to your death?”

I answered, “Well, in the sense that anything is possible, I suppose an accident could happen. But our decisions should be based on what’s probable, not on what’s remotely possible.” My confidence was rational because engineers worked very hard to create the exciting, but safe experience called Edge Walk.

Don’t confuse high confidence with overconfidence. High confidence is helpful; overconfidence is harmful. I had high confidence in the Edge Walk because I completely trusted the equipment and our guide. If I were overconfident, I might have said, “I don’t need the harness; I can do the Edge Walk without it.” Although we don’t want to be overconfident, we shouldn’t stop living courageously. After all, we need confidence, for without it, nothing will be accomplished. In a word, confidence moves us forward, but overconfidence leads to getting stuck in a rut, moving backward, or crashing!

If even experts can suffer from overconfidence, we have all the more reason to be careful. Here are examples of comments made by experts. What do you think; do they sound overconfident?

Lord Kelvin, mathematician and physicist, former president of the British Royal Society:

“X-rays will prove to be a hoax.” (1883)
“Heavier-than-air flying machines are impossible.” (1895)
“Radio has no future.” (1897)
And when speaking to the British Association for the Advancement of Science, he said, “There is nothing new to be discovered in physics now; all that remains is more and more precise measurement.” (1900)

Michigan Savings Bank president advising Henry Ford’s lawyer not to invest in the Ford Motor Co.:

“The horse is here to stay but the automobile is only a novelty, a fad.” (1903)

Scientific American, January 2, 1909

“That the automobile has practically reached the limit of its development is suggested by the fact that during the past year no improvements of a radical nature have been introduced.”

Lee DeForest, American radio innovator and inventor of the vacuum tube

“To place a man in a multi-stage rocket and project him into the controlling gravitational field of the moon where the passengers can make scientific observations, perhaps land alive, and then return to earth − all that constitutes a wild dream worthy of Jules Verne. I am bold enough to say that such a man-made voyage will never occur regardless of all future advances.” (1926)

Admiral William Leahy, U.S. Atomic Bomb Project, advising President Truman on atomic weaponry

“That is the biggest fool thing we have ever done [research on]… The bomb will never go off, and I speak as an expert in explosives.” (1944)

Yale University management professor commenting on a college assignment by Fred Smith who suggested a dependable overnight delivery service. (Smith later established Federal Express Corp.)

“The concept is interesting and well-formed, but in order to earn better than a ‘C’, the idea must be feasible.” (1966)

Business Week, August 2, 1968

“With over fifteen types of foreign cars already on sale here, the Japanese auto industry isn’t likely to carve out a big share of the market for itself.”
If experts can be so terribly wrong, so can we. But if we remain aware of the problem and question our beliefs, we can improve our chances for success.


1. As we grow older and more experienced, we overrate the accuracy of our judgments. Just because we’re older, it doesn’t mean we’re more knowledgeable or wiser. Or as Oscar Wilde (1854~1900) said,

“Experience is the name everyone gives to their mistakes.”

2. The more we know, the more we realize how little we know, and the less we know, the more we think we know.

3. We question the statements of others, but not our own. Get in the habit of challenging your own beliefs. Are they based on facts or just hunches or hearsay?

4. Ironically, we are more likely to get overconfident in areas outside of our expertise. So, think twice before commenting on matters you are unfamiliar with.

5. In your discussions with others, if you find that you’re always right, you’re wrong! In other words, you’re overconfident. So, beware because it will prevent you from learning new things. Remember, we don’t know what we don’t know. Generally, we are unaware of our ignorance until we ask ourselves questions out of curiosity and find that can’t answer them. The way to become more aware of what you do not know is to stop and think every time you disagree with someone. Because if you disagree with what was said, it may be because the person you disagree with knows more about the issue than you do. So, disagreements may be signals of learning opportunities.

6. Overconfident people can easily get stuck in a rut because whenever they fail at something, rather than ask themselves what they are doing wrong, they just keep repeating what they think is right.

7. Don’t try to predict the present or future by the past. Example: “We have always overcome problems in the past, so don’t worry about global warming; when the time comes, I’m sure we will have the technology or knowhow to solve the problem.” This type of thinking doesn’t solve problems; it merely postpones them to a time when it may be too late to correct the problem.

8. Part of the problem is that we all think we are above average. What is the truth? Well, we are better in some areas, but not in areas outside our expertise. Here is an example of how we can be led astray. People who want to lose weight may see an ad in which their favorite celebrities claim to have lost 30+ pounds. The ad may also have a disclaimer “Results not typical.” But overconfident people believe that they are not typical, so the disclaimer does not apply to them. So, overconfident people make excellent targets for sales people. Here’s another example. An office worker joins a gym and signs up for the year to save money. But instead of going to gym two or three times a week, he ends up hardly going at all. Rather than saving money, he winds up losing money. That’s because the overconfident office worker overestimated his self-discipline and willingness to work out. He also confused what he should do with what he will do.

9. To avoid the above problems, know your limitations. You can learn them by monitoring your decisions and their consequences.

10. The more information we are exposed to the more we think we know. In today’s information society we are inundated with facts that come from everywhere: newspapers, magazines, mobile devices, computers, cable TV. As they swirl around us we come to believe we know a great deal more than we really do. There is a big difference between being aware of information and knowing it. It is like the difference between hearing and listening.

Helpful Books to Clear the Cobwebs from Your Mind

The Psychology of Judgment and Decision Making by Scott Plous

Judgment and Decision Making: Psychological Perspectives by David Hardman