Publisher Description

NATIONAL BESTSELLER • From the classroom to the courtroom and from financial markets to supermarkets, an intriguing and illuminating look at how randomness, chance, and probability affect our daily lives that will intrigue, awe, and inspire.

"Mlodinow writes in a breezy style, interspersing probabilistic mind-benders with portraits of theorists.... The result is a readable crash course in randomness." —The New York Times Book Review

With the born storyteller's command of narrative and imaginative approach, Leonard Mlodinow vividly demonstrates how our lives are profoundly informed by chance and randomness and how everything from wine ratings and corporate success to school grades and political polls are less reliable than we believe.

By showing us the true nature of chance and revealing the psychological illusions that cause us to misjudge the world around us, Mlodinow gives us the tools we need to make more informed decisions. From the classroom to the courtroom and from financial markets to supermarkets, Mlodinow's intriguing and illuminating look at how randomness, chance, and probability affect our daily lives will intrigue, awe, and inspire.

Author Biography

Leonard Mlodinow received his doctorate in physics from the University of California, Berkeley, was an Alexander von Humboldt fellow at the Max Planck Institute, and now teaches about randomness to future scientists at Caltech. Along the way he also wrote for the television series MacGyver and Star Trek: The Next Generation. His previous books include Euclid's Window: The Story of Geometry from Parallel Lines to Hyperspace, Feynman's Rainbow: A Search for Beauty in Physics and in Life, and, with Stephen Hawking, A Briefer History of Time. He lives in South Pasadena, California.

Table of Contents

Prologue

Chapter 1: Peering through the Eyepiece of Randomness
The hidden role of chance . . . when human beings can be outperformed by a rat.

Chapter 2: The Laws of Truths and Half-Truths
The basic principles of probability and how they are abused . . . why a good story is often less likely to be true than a flimsy explanation.

Chapter 3: Finding Your Way through a Space of Possibilities
A framework for thinking about random situations . . . from a gambler in plague-ridden Italy to Let's Make a Deal.

Chapter 4: Tracking the Pathways to Success
How to count the number of ways in which events can happen, and why it matters . . . the mathematical meaning of expectation.

Chapter 5: The Dueling Laws of Large and Small Numbers
The extent to which probabilities are reflected in the results we observe . . . Zeno's paradox, the concept of limits, and beating the casino at roulette.

Chapter 6: False Positives and Positive Fallacies
How to adjust expectations in light of past events or new knowledge . . . mistakes in conditional probability from medical screening to the O. J. Simpson trial and the prosecutor's fallacy.

Chapter 7: Measurement and the Law of Errors
The meaning and lack of meaning in measurements . . . the bell curve and wine ratings, political polls, grades, and the position of planets.

Chapter 8: The Order in Chaos
How large numbers can wash out the disorder of randomness . . . or why 200,000,000 drivers form a creature of habit.

Chapter 9: Illusions of Patterns and Patterns of Illusion
Why we are often fooled by the regularities in chance events . . . can a million consecutive zeroes or the success of Wall Street gurus be random?

Chapter 10: The Drunkard's Walk
Why chance is a more fundamental conception than causality . . . Bruce Willis, Bill Gates, and the normal accident theory of life.

Acknowledgments
Notes
Index

Review

"Mlodinow writes in a breezy style, interspersing probabilistic mind-benders with portraits of theorists.... The result is a readable crash course in randomness." —The New York Times Book Review

"A wonderfully readable guide to how the mathematical laws of randomness affect our lives." —Stephen Hawking, author of A Brief History of Time

"[Mlodinow] thinks in equations but explains in anecdote, simile, and occasional bursts of neon. . . . The results are mind-bending." —Fortune

"Even if you begin The Drunkard's Walk as a skeptic, by the time you reach the final pages, you will gain an understanding-if not acceptance-of the intuitively improbable ways that probability biases the outcomes of life's uncertainties." —Barron's

"Delightfully entertaining." —Scientific American 

"A magnificent exploration of the role that chance plays in our lives. The probability is high that you will be entertained and enlightened by this intelligent charmer." —Daniel Gilbert, author of Stumbling on Happiness

"Mlodinow is the perfect guy to reveal the ways unrelated elements can relate and connect." —The Miami Herald

"A primer on the science of probability." —The Washington Post Book World

"Challenges our intuitions about probability and explores how, by understanding randomness, we can better grasp our world." —Seed Magazine

"Mlodinow has an intimate perspective on randomness." —The Austin Chronicle

Review Quote

"Mlodinow writes in a breezy style, interspersing probabilistic mind-benders with portraits of theorists.... The result is a readable crash course in randomness."- The New York Times Book Review "A wonderfully readable guide to how the mathematical laws of randomness affect our lives."-Stephen Hawking, author of A Brief History of Time "[Mlodinow] thinks in equations but explains in anecdote, simile, and occasional bursts of neon. . . . The results are mind-bending."- Fortune "Even if you begin The Drunkard's Walk as a skeptic, by the time you reach the final pages, you will gain an understanding-if not acceptance-of the intuitively improbable ways that probability biases the outcomes of life's uncertainties."- Barron's "Delightfully entertaining."- Scientific American "A magnificent exploration of the role that chance plays in our lives. The probability is high that you will be entertained and enlightened by this intelligent charmer." -Daniel Gilbert, author of Stumbling on Happiness "Mlodinow is the perfect guy to reveal the ways unrelated elements can relate and connect."- The Miami Herald "A primer on the science of probability."- The Washington Post Book World "Challenges our intuitions about probability and explores how, by understanding randomness, we can better grasp our world." - Seed Magazine "Mlodinow has an intimate perspective on randomness."- The Austin Chronicle

Excerpt from Book

Peering through the Eyepiece of Randomness I remember, as a teenager, watching the yellow flame of the Sabbath candles dancing randomly above the white paraffin cylinders that fueled them. I was too young to think candlelight romantic, but still I found it magical-because of the flickering images created by the fire. They shifted and morphed, grew and waned, all without apparent cause or plan. Surely, I believed, there must be rhyme and reason underlying the flame, some pattern that scientists could predict and explain with their mathematical equations. "Life isn''t like that," my father told me. "Sometimes things happen that cannot be foreseen." He told me of the time when, in Buchenwald, the Nazi concentration camp in which he was imprisoned and starving, he stole a loaf of bread from the bakery. The baker had the Gestapo gather everyone who might have committed the crime and line the suspects up. "Who stole the bread?" the baker asked. When no one answered, he told the guards to shoot the suspects one by one until either they were all dead or someone confessed. My father stepped forward to spare the others. He did not try to paint himself in a heroic light but told me that he did it because he expected to be shot either way. Instead of having him killed, though, the baker gave my father a plum job, as his assistant. "A chance event," my father said. "It had nothing to do with you, but had it happened differently, you would never have been born." It struck me then that I have Hitler to thank for my existence, for the Germans had killed my father''s wife and two young children, erasing his prior life. And so were it not for the war, my father would never have emigrated to New York, never have met my mother, also a refugee, and never have produced me and my two brothers. My father rarely spoke of the war. I didn''t realize it then, but years later it dawned on me that whenever he shared his ordeals, it was not so much because he wanted me to know of his experiences but rather because he wanted to impart a larger lesson about life. War is an extreme circumstance, but the role of chance in our lives is not predicated on extremes. The outline of our lives, like the candle''s flame, is continuously coaxed in new directions by a variety of random events that, along with our responses to them, determine our fate. As a result, life is both hard to predict and hard to interpret. Just as, looking at a Rorschach blot, you might see Madonna and I, a duck-billed platypus, the data we encounter in business, law, medicine, sports, the media, or your child''s third-grade report card can be read in many ways. Yet interpreting the role of chance in an event is not like intepreting a Rorschach blot; there are right ways and wrong ways to do it. We often employ intuitive processes when we make assessments and choices in uncertain situations. Those processes no doubt carried an evolutionary advantage when we had to decide whether a saber-toothed tiger was smiling because it was fat and happy or because it was famished and saw us as its next meal. But the modern world has a different balance, and today those intuitive processes come with drawbacks. When we use our habitual ways of thinking to deal with today''s tigers, we can be led to decisions that are less than optimal or even incongruous. That conclusion comes as no surprise to those who study how the brain processes uncertainty: many studies point to a close connection between the parts of our brain that make assessments of chance situations and those that handle the human characteristic that is often considered our prime source of irrationality-our emotions. Functional magnetic resonance imaging, for example, shows that risk and reward are assessed by parts of the dopaminergic system, a brain-reward circuit important for motivational and emotional processes. The images show, too, that the amygdala, which is also linked to our emotional state, especially fear, is activated when we make decisions couched in uncertainty. The mechanisms by which people analyze situations involving chance are an intricate product of evolutionary factors, brain structure, personal experience, knowledge, and emotion. In fact, the human response to uncertainty is so complex that sometimes different structures within the brain come to different conclusions and apparently fight it out to determine which one will dominate. For example, if your face swells to five times its normal size three out of every four times you eat shrimp, the "logical" left hemisphere of your brain will attempt to find a pattern. The "intuitive" right hemisphere of your brain, on the other hand, will simply say "avoid shrimp." At least that''s what researchers found in less painful experimental setups. The game is called probability guessing. In lieu of toying with shrimp and histamine, subjects are shown a series of cards or lights, which can have two colors, say green and red. Things are arranged so that the colors will appear with different probabilities but otherwise without a pattern. For example, red might appear twice as often as green in a sequence like red-red-green-red-green-red-red-green-green-red-red-red, and so on. The task of the subject, after watching for a while, is to predict whether each new member of the sequence will be red or green. The game has two basic strategies. One is to always guess the color that you notice occurs more frequently. That is the route favored by rats and other nonhuman animals. If you employ this strategy, you are guaranteed a certain degree of success but you are also conceding that you will do no better. For instance, if green shows up 75 percent of the time and you decide to always guess green, you will be correct 75 percent of the time. The other strategy is to "match" your proportion of green and red guesses to the proportion of green and red you observed in the past. If the greens and reds appear in a pattern and you can figure out the pattern, this strategy enables you to guess right every time. But if the colors appear at random, you would be better off sticking with the first strategy. In the case where green randomly appears 75 percent of the time, the second strategy will lead to the correct guess only about 6 times in 10. Humans usually try to guess the pattern, and in the process we allow ourselves to be outperformed by a rat. But there are people with certain types of post-surgical brain impairment-called a split brain-that precludes the right and left hemispheres of the brain from communicating with each other. If the probability experiment is performed on these patients such that they see the colored light or card with only their left eye and employ only their left hand to signal their predictions, it amounts to an experiment on the right side of the brain. But if the experiment is performed so as to involve only their right eye and right hand, it is an experiment on the left brain. When researchers performed those experiments, they found that-in the same patients-the right hemisphere always chose to guess the more frequent color and the left hemisphere always tried to guess the pattern. Making wise assessments and choices in the face of uncertainty is a rare skill. But like any skill, it can be improved with experience. In the pages that follow, I will examine the role of chance in the world around us, the ideas that have been developed over the centuries to help us understand that role, and the factors that often lead us astray. The British philosopher and mathematician Bertrand Russell wrote, We all start from "naive realism," i.e., the doctrine that things are what they seem. We think that grass is green, that stones are hard, and that snow is cold. But physics assures us that the greenness of grass, the hardness of stones, and the coldness of snow are not the greenness of grass, the hardness of stones, and the coldness of snow that we know in our own experience, but something very different. In what follows we will peer at life through the eyepiece of randomness and see that many of the events of our lives, too, are not quite what they seem but rather something very different. In 2002 the Nobel committee awarded the Nobel Prize in Economics to a scientist named Daniel Kahneman. Economists do all sorts of things these days-they explain why teachers are paid so little, why football teams are worth so much, and why bodily functions help set a limit on the size of hog farms (a hog excretes three to five times as much as a human, so a farm with thousands of hogs on it often produces more waste than the neighboring cities). Despite all the great research generated by economists, the 2002 Nobel Prize was notable because Kahneman is not an economist. He is a psychologist, and for decades, with the late Amos Tversky, Kahneman studied and clarified the kinds of misperceptions of randomness that fuel many of the common fallacies I will talk about in this book. The greatest challenge in understanding the role of randomness in life is that although the basic principles of randomness arise from everyday logic, many of the consequences that follow from those principles prove counterintuitive. Kahneman and Tversky''s studies were themselves spurred by a random event. In the mid-1960s, Kahneman, then a junior psychology professor at Hebrew University, agreed to perform a rather unexciting chore: lecturing to a group of Israeli air force flight instructors on the conventional wisdom of behavior modification and its application to the psychology of flight training. Kahneman drove home the point that rewarding positive behavior works but punishing mistakes does not. One of his students interrupted, voicing an opinion that would lead Kahneman to an epiphany and guide his research fo

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