The Drunkard’s Walk

The Drunkard’s Walk: How Randomness Rules Our Lives

Author: Leonard Mlodinow



This book makes the bold assertion that life’s outcomes are largely down to random chance. The author, a physicist, explores the pervasive influence of randomness and argues that success or failure in most of life’s endeavours is mainly arbitrarily determined. He maintains that ‘…a lot of what happens to us-success in our careers, in our investments, and in our life decisions…is as much the result of random factors as the result of skill, preparedness, and hard work’ (page 11).




The book discusses the wide variety of fallacies that account for the human tendency to seek explanations for random events and outcomes. Winning streaks for example are the product of the gambler’s fallacy (page 174), and disease clusters are explained by the Texas sharpshooter fallacy (page 184). The book maintains that these false explanations serve to give people a sense of control over their lives, this itself being a fallacy termed the illusion of control. The author however explains that this illusion is key to the maintenance of self-esteem and, citing the psychologist Ellen Langer’s mindfulness studies, shows that it helps to sustain good health (page 186).



Why don’t humans appreciate the effect of randomness? The author attributes our failure to notice the influence of chance to the human tendency to perceive non-existent associations and patterns. He says ‘…the human mind is built to identify, for each event, a definite cause and can therefore have a hard time accepting the influence of unrelated or random factors’ (page xi). Furthermore, a poor concept of probability blinds us to the pervasiveness of random events (page 119). The author says people are particularly prone to over-estimate the odds of well-described events; he supports this with the famous Linda problem posed by the psychologists Daniel Kahneman and Amos Tversky. The author also furnishes real-life examples such as doctors wrongly estimating the risk of pulmonary embolism (page 25).

Dice. Jayen Pancholi on Flikr.

Our misperception of arbitrary events is sustained by a variety of human biases. The author gives the example of confirmation bias; people look for evidence to support their pre-formed opinions and overlook evidence supporting the contrary view. The author quoted the philosopher Francis Bacon who observed that a man will fail to notice or will dismiss disconfirming evidence ‘…in order that his opinion will remain unshaken’ (page 189). The hindsight bias on the other hand creates an ‘illusion of inevitability’; referring to the historian Roberta Wohlstetter, the author shows that hindsight enables people to make wrong associations to explain away situations that are otherwise ‘…obscure and pregnant with conflicting meanings…’ (page 201)..

The Monty Hall problem. By The original uploader was Kuxu at French Wikipedia [GFDL ( or CC-BY-SA-3.0 (], via Wikimedia Commons
The Monty Hall problem. By The original uploader was Kuxu at French Wikipedia [GFDL ( or CC-BY-SA-3.0 (, via Wikimedia Commons

The author illustrates his arguments with several real-life examples. The Monty Hall problem and the-girl-named-Florida problem for example illustrate the human tendency to misjudge probabilities. He used the OJ Simpson murder trial and the Sally Clark miscarriage of justice case to explore the problem of ‘inversion’. Relevant to healthcare is his discussion of false positive test results, an issue many doctors fail to comprehend. The book addresses pertinent psychological concepts such regression to the mean (page 8) and Bayes theorem of conditional probabilities (page 106). He also reviewed relevant mathematical concepts with appropriate anecdotes; these are typically of interesting historical personalities such as Galileo, Gerolamo Cordano, Blaise Pascal, Pierre Fermat, and Jakob Bernoulli.” target=”_blank”>

The author speaking on his book at google


Other books, prominently Nassim Nicholas Taleb‘s Fooled by Randomness, have explored the issue of randomness and this is a great addition to the literature. The author highlights the fallacies and biases that blur our appreciation of randomness and he discusses this important concept in an interesting way. The degree to which randomness affects outcomes is probably a controversial issue, and the book just falls short of under-estimating the contribution of personal effort. I struggled to grasp some of the mathematical concepts which are, perhaps, not aimed at the casual reader; this nevertheless did not detract from understanding their implications. The author narrates very interesting anecdotes although at times, as with the story of Gerolamo Cordano, in too much detail.


The book highlights the wide-spread influence of arbitrary events on life’s outcomes. The author illustrates his arguments with interesting anecdotes and established facts. The concepts of randomness and probabilities are core to healthcare and this well-written book explains them clearly. I therefore recommend the book to all doctors.


  • Publisher, place, date: Penguin, London, 2009
  • Edition: 1st
  • Number of chapters: 10
  • Pages: 252
  • ISBN: 987-0-141-02647-3
  • Price: £7.49
  • Star rating: 5 stars




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