The ideas in this book have created more controversy than they deserve, and it might have something to do with the title of the book. Given the number of people who equate "random" with "equiprobable", "Fooled by Probabilities" would have been a more appropriate title for the book, though not as provocative as "Fooled by Randomness". There is a finite chance that there is a black cat in every dark room, but when you switch the light on, there is no black cat in the room. Both are correct statements - mathematically and practically. This book must be read in the same light.
It seems to me that the transition from an average to good investor (probabilistically speaking) happens as soon as you internalize the concept of expected values and invest by it. My favorite story from the book is where Taleb is asked which way the market is expected to go next week, and he says slightly up with a high probability (70%). Then someone intervened that Taleb had just made a big bet on the S&P going down next week, and he said that indeed he did. The one lesson this book teaches is that the two statements are not inconsistent with each other. 70% chance of a +1% change and 30% chance of a -10% change sums upto -2.3, a strongly negative expected value. Good investors always shadow the expected value (trend and magnitude), although market sentiments are always driven by either the expected trend of upward or downward movement, or expected magnitude of upward and downward movement.
Four key insights that I received from the book about how we all get fooled by probabilities in our everyday lives are the firehouse effect, survivorship bias, endowment effect and Wittgenstein's ruler. Firehouse effect is characterized by a clique of people with much downtime (firemen) who end up strongly agreeing with each other about things that would seem incorrect to any rational observer - something that many investors suffer from. The survivorship bias talks about exclusion of failures from "objective" after-the-fact performance studies - something that many business books suffer from. Endowment effect suggests that people value something more after they own it or get familiar with it - something that many businesses suffer from. Wittgenstein's ruler says that when an unreliable ruler is used to measure a table, the table is measuring the ruler and not the other way around. Reliability of the ruler determines what is being measured - something that consumer reviews and stock recommendations suffer from. For these and many such, read Fooled by Randomness.
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