Test your confidence
Try to answer the following questions, not by giving the exact answer, but by giving a range for which you are 90% sure that contains the correct answer. For example:
- How many member states did United Nations have in 2010?
Suppose you think that the answer is somewhere around 150. Now, you just need to write a range within which you are 90% sure the correct number will be. For example, confident people would answer with "140 — 170". If you're not that sure, it would be better to answer "100 — 200". Answering "0 — 999 999" would be an exaggeration, because you need to aim for a 10-percent risk that you won't answer correctly. (By the way, the exact number is 193.)
These are not trick questions. No need for looking online or asking other people — if you are unsure about your answer, just write in a wider range. If you don't have any idea what would be the right answer, try to logically determine in what range it should be, but leave a 10% chance of getting it wrong. And take as much time as you wish.
Here are the questions:
- What is the greatest known ocean depth on Earth? 10911 m http://en.wikipedia.org/wiki/Challenger_Deep
- How many stone blocks were used to build the Great Pyramid of Giza? 2300000 blocks http://en.wikipedia.org/wiki/Great_Pyramid_of_Giza
- In how many of his movies does Alfred Hitchcock make a cameo appearance? 39 times http://en.wikipedia.org/wiki/List_of_Hitchcock_cameo_appearances
- How long is the Trans-Siberian Railway? 9260 km http://en.wikipedia.org/wiki/Trans-Siberian_Railway
- What year was Beethoven born? 1770 http://en.wikipedia.org/wiki/Ludwig_van_Beethoven
- What year did Michelangelo finished his statue of David? 1504 http://en.wikipedia.org/wiki/David_(Michelangelo)
- How long is the river Nile? 6650 km http://en.wikipedia.org/wiki/Nile
- What's the maximum takeoff weight of Boeing 747-400? 397 tons http://www.boeing.com/commercial/747family/pf/pf_400_prod.html
- How long is the gestation period (pregnancy) of an African elephant? 22 months http://en.wikipedia.org/wiki/Elephant
- What is the mean diameter of the Moon? 3475 km http://en.wikipedia.org/wiki/Moon
You had ? wrong and ? right answers, so your accuracy is ? percent. Realistic estimates would have the accuracy of about 90%.
OK, now what?
This test should show you that you are overconfident. Specifically, when we analyze how people respond to such questions, it turns out that the number of wrong answers is much higher than would be expected if they have realistically assessed how large should their safety margin be. Your individual test results may be the result of chance, but when we look at total numbers of lots of people, excessive self-confidence cannot be written off as coincidence.
Studies show that we as a species tend to overestimate their abilities. Here are some examples:
- The classic studies of this type, respondents estimated the statistics of things like egg production or the number of doctors working in the city. Although the ranges were adjusted to allow mistakes to occur only 2% of the time, actual frequency of errors was 46%.
- In the spelling test, of all words for which the respondents said they are 100% sure that they got right there were 20% of misspelled words.
- Medics who had diagnosed pneumonia in their patients were on average 88% sure they are right. In fact, only 20% of patients actually had pneumonia.
- 70 to 90% of drivers consider themselves above-average drivers.
Alpert, Marc; Howard Raiffa: A progress report on the training of probability assessors. U zborniku "Judgment under uncertainty: Heuristics and biases".
Iain A. McCormick, Frank H. Walkey, Dianne E. Green: Comparative perceptions of driver ability — A confirmation and expansion. Accident Analysis & Prevention
Adams, P. A., & Adams, J. K. Confidence in the recognition and reproduction of words difficult to spell. The American Journal of Psychology
Karen M. O'Keefe, Barbara M. Wildemuth, Charles P. Friedman: Medical students' confidence judgments using a factual database and personal memory: A comparison. Journal of the American Society for Information Science
Why are we overconfident? Does it help us in our lives? Such an unrealistic assessment of our abilities can easily get us in trouble: we will take on tasks that we cannot complete, engage in more risk than you are willing to accept, expect that our efforts will pay off more than we should. It is believed that without that irrational tendency, there would be far fewer lawsuits, strikes, financial crashes, and even wars — if both sides are able to realistically assess their options, the deal would be much more practical option than fighting.
Buehler, R., Griffin, D., & Ross, M.: Exploring the "planning fallacy": Why people underestimate their task completion times. Journal of Personality and Social Psychology PDF
And yet another indication of how our own mind is deceptive: The study states that the respondents were overconfident even after being alerted to this effect. This reminds me of Hofstadter's law
Everything always takes longer than you expect, even when you take into account Hofstadter's law.