According to the pioneering work of  Kahneman e Tverski, humans make choices by means of heuristic cognitive strategies rather than rational cognitive strategies. This approach is even more evident when we consider the so called “illusory superiority” or “above-average effect”, condition of cognitive bias  wherein people overestimates their own qualities and abilities, in relation to the same qualities and abilities of other people.  

A series of experiments have been performed over the years in order to analyze this bias.

Several groups of people in Sweden and USA have been surveyed, asking them to compare their driving skills and safety to other people’s. 80-90% of the interviewed people have scored themselves above the average.

In another experiment a group of students was interviewed about how they forecast their own future and the futures of their peers. Most of the students held optimistic views of their own future: successful job, happy marriage and health children. But they held frequently pessimistic views of the peer’s future: alcohol addiction, diseases, divorces, etc. 

In the best seller “In search of Excellence”, Peters and Waterman wrote to have interviewed a random sample  of adult males about their ability to get on well with others. 100% of the interviewed males claimed to be above the average, and 25% of them ranked themselves in the top 1%.

Khaneman e Tverski have shown that this illusory bias is a typical feature of the stock traders: they overvalue their own forecasting abilities and control of the future events, underestimating the role of luck.