The Drunkard's Walk is a fascinating book, but it is so maddening at times that I wished I had the author, Leonard Mlodinow, on the phone to elaborate on his conclusions and convince me that what he says is logically sound. As it is, I was on my own, which is unfortunate considering the great number of insightful ideas explored in the book.
The ultimate objective of The Drunkard's Walk is to bring to light the great effect that random chance (or luck) has on our everyday lives. We so often ignore or misunderstand this effect that Mlodinow's effort is vital. The issue of randomness isn't the sole domain of statisticians, physicists, and gamblers; we all have to make decisions based on our understanding of randomness and probability, and these decisions could come in life-or-death situations. Mlodinow asks us not to panic and points out that recognizing our prejudices or erroneous thinking is the first step in correcting it.
The Drunkard's Walk goes to great lengths to define these mistakes and to explain them. The biggest mistake we make comes from our overdeveloped sense of pattern recognition. Obviously, a strong sense of pattern recognition serves a strong evolutionary purpose; by learning which actions do or do not achieve a desired result, we succeed - or at least we should.
The Drunkard's Walk describes an experiment in which subjects were shown two sets of cards: red and green. Red cards show up roughly twice as often as green. The observer is then asked to predict, based on the previous sequence, what color will come up next. Most humans will try to figure out the pattern, even if there isn't one evident. Some will try to guess which is next based on the last few cards: if four reds show up in a row, then a green must be "due." Other people will act according to their understanding of probability: they'll guess red two-thirds of the time since it occurs two-thirds of the time.
The most successful strategy is to keep guessing red because regardless of the previous sequence, red will always be the most likely card to appear next. Rats, when confronted with a similar experiment, get it right more often than we do. Humans, with our amazing brainpower, are thus thwarted by an elementary tenet of probability.