The gist of Taleb’s book can be explained, at the risk of oversimplification, by using a few examples rooted in basic probability of the kind that relies on a simple coin toss experiment. Suppose one tosses a fair coin 5 times, with a reward associated with getting 5 consecutive heads. The probability associated with this outcome is 1/32. Now suppose that there are 32 people similarly tossing a coin each 5 times. There exists a high probability of one of them obtaining the desired 5 heads, and getting the reward. The other participants, assuming they are ignorant of the underlying probability, may attribute this victory to a certain talent possessed by the winner. Similarly, the winner may be led to believe that his winnings are due to his own talents. This is what Taleb refers to when he talks about being fooled by randomness.
Another interesting concept in the book is that of alternate histories. In the earlier example, instead of 32 people, consider just one person tossing the coin 5 times each on 32 different occasions. In this case, each of these 32 occasions can be considered as being an alternate history. In obtaining a certain outcome of the 5 tosses, one has essentially chose one of 32 alternate histories, of which one may lead to a success and the others end up in failures.
Taleb also talks about the black swan – the occurrence of a rare event. The significance of the rare event is best explained using the example in the first paragraph. Suppose that instead of a reward associated with getting 5 heads, there is now a large penalty associated with getting 5 heads (say $95), and a small reward associated with each of the other outcomes (say $1). In this case, the expected payoff will be – $2, and hence it is not worth accepting such a proposition. However, the tendency to focus more on frequency of outcomes while ignoring their outcomes, often leads people to take up such risky propositions with potentially damaging outcomes.
Some of the other concepts invoked in this book that I found interesting include the biases: survivorship bias (ignorance of failed outcomes), hindsight bias (overestimation of what one knew at the time of a past event due to subsequent information) and attribution bias (attributing personal success to talent and failure to randomness).
The above are just a sampling of the many ideas that Taleb draws on, in his book. The examples used are far more interesting than the simple one that I have used above. Taleb begins by explaining the rational basis for what is often random but perceived otherwise, and then he goes on to discuss the behavioral aspects that lead to such mistaken perceptions. At the end of the book, he brings up the key question of whether it is possible to be completely rational, and the repercussions, both positive and negative, of such an outlook.
An eminent financial mathematician in his own right, Taleb is evidently well read, drawing from a range of subjects that includes philosophy and mythology, to economics, behavioral finance, and mathematics. My only criticism about this book is that one often finds more of the author writing about himself than the ideas he expounds. That apart, the book remains an enlightening and engrossing read.
Filed under: books, finance | Tagged: cognitive bias, fooled by randomness, nassim taleb, probability | 1 Comment »