Planning our activities and confidence in our knowledge, i.e. how we overestimate ourselves


Published: 07-11-2021

In my article on self-serving bias, I mentioned that we often unfoundedly consider ourselves superior to others, but even when we do not compare ourselves to anyone, we tend to overestimate ourselves.

Our tendency to overestimate ourselves can be seen very clearly in the example of planning our activities. Mostly we are convinced that we will finish our work sooner than we actually finish it. Psychology students in their final year were once asked how long it would take for them to write their diploma thesis. They were asked to estimate how long it was likely to take them and how much time they would have to spend “if everything goes as well as it can” and how much “if everything goes as bad as it can”. Only less than 50% fit in their estimate in case of problems. So more than 50 percent of the students did worse than they could have imagined before … On average, students estimated that they needed 33.9 more days, and in fact it took an average of 55.5 days, so their estimated time increased by 34% (Buehler, Griffin, Ross, 1994). The same researchers also asked about non-academic work, such as repairing a bicycle, cleaning an apartment, or writing a letter to a friend. The results were similar. People are notoriously falling short of the time they set themselves up. Interestingly, people don’t seem to have the ability to learn from mistakes. Since we are late so many times and we never do anything ahead of schedule, we should learn to allocate more time to get things done. But no. Still and still we overestimate ourselves.

This overestimation in planning is also visible in many construction projects. How many times have heard the promises about a motorway, subway, road repair or anything else, and then have the deadline been postponed many times? But those who think that it is only a Polish domain are wrong… other countries can also boast of their inability to plan. For example, the Sydney Opera House was expected to cost $ 7 million and was to be completed in 1963, and it was actually completed in 1973 at a cost of $ 102 million (Hall, 1980 from Buehler, Griffin, & Ross, 1994).

In addition to overestimating our ability to meet the scheduled date, we also often overestimate our knowledge. Russo and Schoemaker (1989 as cited in: Tyszka, 1999) constructed a test showing how well we can assess our own knowledge. The test consists of ten questions, e.g. what is the length of the river Nile, how many books of the Old Testament is, how many days is pregnancy in an Asian elephant, in which year Mozart was born. Hardly anyone knows the correct answers to all these types of questions, but the test is not about answering correctly every kilometer or day, but about correctly assessing the certainty of your answer. As an answer, the person has to enter the range of 90% certainty. So if you are 90% sure that the Nile River is between 1000 km and 10,000 km, these are the values ​​you should enter as your answer. If the correct answer is within this range, your answer is scored. There is no requirement whatsoever as to the width of the range that can be created, it is only the requirement that only 1 question out of 10 may be answered incorrectly. Nevertheless, almost everyone makes a few mistakes in the test, which proves that we think we know more than we actually know. We are more confident in our answers than we should be given our actual knowledge. (For those interested: the Nile is 7754 km long, there are 46 books of the Old Testament, the pregnancy of the Asian elephant lasts 645 days, and Mozart was born in 1756).

Much research has been done into the unreasonable certainty of one’s knowledge. Some used the Russo and Schoemaker test, while others were asked test questions with two or more choices, and then asked the respondent to what percentage is confident in the selected answer. Research unanimously shows that people are not able to correctly assess their knowledge and their certainty of answers often has little to do with the truthfulness of the answers. Even when the respondents declare that they are 100% sure of their answer, about 20-30% of their answer is incorrect (Lichtenstein, Fischhoff, 1977 as cited in: Tyszka, 1999). Overconfident in their knowledge are less intelligent and more intelligent, experts in the field and laymen… a common ailment.


  1. Buehler, R., Griffin, D., Ross, M. (1994). Exploring the „Planning fallacy”: Why people underestimate their task completion times. Journal of Personality and Social Psychology, 67(3), 366-381.
  2. Tyszka, T. (1999). Psychologiczne pułapki oceniania i podejmowania decyzji. Gdańsk: Gdańskie Wydawnictwo Psychologiczne.

Author: Maja Kochanowska

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