Everything is Obvious E-Book

Duncan J. Watts

• Herausgeber: Atlantic Books
• Kategorie: Fachliteratur
• Sprache: Englisch

Veröffentlichungsjahr: 2011

Beschreibung

Why is the Mona Lisa the most famous painting in the world? Why did Facebook succeed when other social networking sites failed? Did the surge in Iraq really lead to less violence? And does higher pay incentivize people to work harder? If you think the answers to these questions are a matter of common sense, think again. As sociologist and network science pioneer Duncan Watts explains in this provocative book, the explanations that we give for the outcomes that we observe in life-explanations that seem obvious once we know the answer-are less useful than they seem. Watts shows how commonsense reasoning and history conspire to mislead us into thinking that we understand more about the world of human behavior than we do; and in turn, why attempts to predict, manage, or manipulate social and economic systems so often go awry. Only by understanding how and when common sense fails can we improve how we plan for the future, as well as understand the present-an argument that has important implications in politics, business, marketing, and even everyday life.

Leseprobe

Everything is Obvious

Duncan J. Watts is a principal research scientist at Yahoo! Research, and a former professor of sociology at Columbia University. His research on social networks and collective dynamics has appeared in a wide range of academic journals, including Nature, Science, and the American Journal of Sociology. He lives in New York.

Also by Duncan J. Watts:

Six Degrees: The Science of a Connected Age Small Worlds: The Dynamics of Networks between Order and Randomness

EVERYTHING IS OBVIOUS

How Common Sense Fails

Duncan J. Watts

First published in the United States of America in 2011 by Crown Business, a division of Random House Ltd.

First published in Great Britain in 2011 by Atlantic Books, an imprint of Atlantic Books Ltd.

Copyright © Duncan J. Watts, 2011

The moral right of Duncan J. Watts to be identified as the author of this work has been asserted by him in accordance with the Copyright, Designs and Patents Act of 1988.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of both the copyright owner and the above publisher of this book.

Every effort has been made to trace or contact all copyright holders. The publishers will be pleased to make good any omissions or rectify any mistakes brought to their attention at the earliest opportunity.

10 9 8 7 6 5 4 3 2 1

A CIP catalogue record for this book is available from the British Library.

Hardback ISBN: 978 1 84887 2141

Trade Paperback ISBN: 978 1 84887 2158 eBook ISBN: 978 0 85789 5066

Printed in Great Britain

Atlantic Books An imprint of Atlantic Books Ltd Ormond House 26–27 Boswell Street London WC1N 3JZwww.atlantic-books.co.uk

For Jack and Lily

CONTENTS

PREFACE A Sociologist’s Apology

PART I COMMON SENSE

CHAPTER 1 The Myth of Common Sense

CHAPTER 2 Thinking About Thinking

CHAPTER 3 The Wisdom (and Madness) of Crowds

CHAPTER 4 Special People

CHAPTER 5 History, The Fickle Teacher

CHAPTER 6 The Dream of Prediction

PART II UNCOMMON SENSE

CHAPTER 7 The Best-Laid Plans

CHAPTER 8 The Measure of All Things

CHAPTER 9 Fairness and Justice

CHAPTER 10 The Proper Study of Mankind

ACKNOWLEDGMENTS

BIBLIOGRAPHY

NOTES

INDEX

PREFACE

A Sociologist’s Apology

In January 1998, about halfway through my first year out of graduate school, my housemate at the time handed me a copy of New Scientist magazine containing a book review by the physicist and science writer John Gribbin. The book Gribbin was reviewing was called Tricks of the Trade, by the Chicago sociologist Howard Becker, and was mostly a collection of Becker’s musings on how to do productive social science research. Gribbin clearly hated it, judging Becker’s insights to be the kind of self-evident checks that “real scientists learn in the cradle.” But he didn’t stop there. He went on to note that the book had merely reinforced his opinion that all of social science was “something of an oxymoron” and that “any physicist threatened by cuts in funding ought to consider a career in the social sciences, where it ought to be possible to solve the problems the social scientists are worked up about in a trice.”1

There was a reason my roommate had given me this particular review to read and why that particular line stuck in my head. I had majored in physics at college, and at the time when I read Gribbin’s review I had just finished my PhD in engineering; I had written my dissertation on the mathematics of what are now called small-world networks.2 But although my training had been in physics and mathematics, my interests had turned increasingly toward the social sciences and I was just beginning what turned out to be a career in sociology. So I felt that in a sense I was embarking on a miniature version of Gribbin’s proposed experiment. And to be honest, I might have suspected that he was right.

Twelve years later, however, I think I can say that the problems sociologists, economists, and other social scientists are “worked up about” are not going to be solved in a trice, by me or even by a legion of physicists. I say this because since the late 1990s many hundreds, if not thousands of physicists, computer scientists, mathematicians, and other “hard” scientists have taken an increasing interest in questions that have traditionally been the province of the social sciences—questions about the structure of social networks, the dynamics of group formation, the spread of information and influence, or the evolution of cities and markets. Whole fields have arisen over the past decade with ambitious names like “network science” and “econophysics.” Datasets of immense proportions have been analyzed, countless new theoretical models have been proposed, and thousands of papers have been published, many of them in the world’s leading science journals, such as Science, Nature, and Physical Review Letters. Entire new funding programs have come into existence to support these new research directions. Conferences on topics such as “computational social science” increasingly provide forums for scientists to interact across old disciplinary boundaries. And yes, many new jobs have appeared that offer young physicists the chance to explore problems that once would have been deemed beneath them.

The sum total of this activity has far exceeded the level of effort that Gribbin’s offhand remark implied was required. So what have we learned about those problems that social scientists were so worked up about back in 1998? What do we really know about the nature of deviant behavior or the origins of social practices or the forces that shift cultural norms—the kinds of problems that Becker talks about in his book—that we didn’t know then? What new solutions has this new science provided to real-world problems, like helping relief agencies respond more effectively to humanitarian disasters in places like Haiti or New Orleans, or helping law enforcement agencies stop terrorist attacks, or helping financial regulatory agencies police Wall Street and reduce systemic risk? And for all the thousands of papers that have been published by physicists in the past decade, how much closer are we to answering the really big questions of social science, like the economic development of nations, the globalization of the economy, or the relationship between immigration, inequality, and intolerance? Pick up the newspaper and judge for yourself, but I would say not much.3

If there’s a lesson here, you might think it would be that the problems of social science are hard not just for social scientists, but for physicists as well. But this lesson, it seems, has not been learned. Quite to the contrary, in fact, in 2006 Senator Kay Bailey Hutchison, a Republican from Texas, proposed that Congress cut the entire social and behavioral sciences budget of the National Science Foundation. Bailey Hutchison, it should be noted, is not antiscience—in 2005 she proposed doubling funds for medical science. Rather, it was exclusively social science research that she felt “is not where we should be directing [NSF] resources at this time.” Ultimately the proposal was defeated, but one might still wonder what the good senator was thinking. Presumably she doesn’t think that social problems are unimportant—surely no one would argue that immigration, economic development, and inequality are problems that are somehow unworthy of attention. Rather it appears that, like Gribbin, she doesn’t consider social problems to be scientific problems, worthy of the prolonged attention of serious scientists. Or as Hutchinson’s colleague from Oklahoma, Senator Tom Coburn, put it three years later in a similar proposal, “Theories on political behavior are best left to CNN, pollsters, pundits, historians, candidates, political parties, and the voters.”4

Senators Hutchinson and Coburn are not alone in their skepticism of what social science has to offer. Since becoming a sociologist, I have frequently been asked by curious outsiders what sociology has to say about the world that an intelligent person couldn’t have figured out on their own. It’s a reasonable question, but as the sociologist Paul Lazarsfeld pointed out nearly sixty years ago, it also reveals a common misconception about the nature of social science. Lazarsfeld was writing about The American Soldier, a then-recently published study of more than 600,000 servicemen that had been conducted by the research branch of the war department during and immediately after the Second World War. To make his point, Lazarsfeld listed six findings from the study that he claimed were representative of the report. For example, number two was that “Men from rural backgrounds were usually in better spirits during their Army life than soldiers from city backgrounds.” “Aha,” says Lazarsfeld’s imagined reader, “that makes perfect sense. Rural men in the 1940s were accustomed to harsher living standards and more physical labor than city men, so naturally they had an easier time adjusting. Why did we need such a vast and expensive study to tell me what I could have figured out on my own?”

Why indeed. . . . But Lazarsfeld then reveals that all six of the “findings” were in fact the exact opposite of what the study actually found. It was city men, not rural men, who were happier during their Army life. Of course, had the reader been told the real answers in the first place she could just as easily have reconciled them with other things that she already thought she knew: “City men are more used to working in crowded conditions and in corporations, with chains of command, strict standards of clothing and social etiquette, and so on. That’s obvious!” But that’s exactly the point that Lazarsfeld was making. When every answer and its opposite appears equally obvious, then, as Lazarsfeld put it, “something is wrong with the entire argument of ‘obviousness.’ ”5

Lazarsfeld was talking about social science, but what I will argue in this book is that his point is equally relevant to any activity—whether politics, business, marketing, philanthropy—that involves understanding, predicting, changing, or responding to the behavior of people. Politicians trying to decide how to deal with urban poverty already feel that they have a pretty good idea why people are poor. Marketers planning an advertising campaign already feel that they have a decent sense of what consumers want and how to make them want more of it. And policy makers designing new schemes to drive down healthcare costs or to improve teaching quality in public schools or to reduce smoking or to improve energy conservation already feel that they can do a reasonable job of getting the incentives right. Typically people in these positions do not expect to get everything right all the time. But they also feel that the problems they are contemplating are mostly within their ability to solve—that “it’s not rocket science,” as it were.6 Well, I’m no rocket scientist, and I have immense respect for the people who can land a machine the size of a small car on another planet. But the sad fact is that we’re actually much better at planning the flight path of an interplanetary rocket than we are at managing the economy, merging two corporations, or even predicting how many copies of a book will sell. So why is it that rocket science seems hard, whereas problems having to do with people—which arguably are much harder—seem like they ought to be just a matter of common sense? In this book, I argue that the key to the paradox is common sense itself.

Criticizing common sense, it must be said, is a tricky business, if only because it’s almost universally regarded as a good thing—when was the last time you were told not to use it? Well, I’m going to tell you that a lot. As we’ll see, common sense is indeed exquisitely adapted to handling the kind of complexity that arises in everyday situations. And for those situations, it’s every bit as good as advertised. But “situations” involving corporations, cultures, markets, nation-states, and global institutions exhibit a very different kind of complexity from everyday situations. And under these circumstances, common sense turns out to suffer from a number of errors that systematically mislead us. Yet because of the way we learn from experience—even experiences that are never repeated, or that take place in other times and places—the failings of commonsense reasoning are rarely apparent to us. Rather, they manifest themselves to us simply as “things we didn’t know at the time” but which seem obvious in hindsight. The paradox of common sense, therefore, is that even as it helps us make sense of the world, it can actively undermine our ability to understand it. If you don’t quite understand what that last sentence means, that’s OK, because explaining it, along with its implications for policy, planning, forecasting, business strategy, marketing, and social science is what the rest of this book is about.

Before I start, though, I would like to make one related point: that in talking with friends and colleagues about this book, I’ve noticed an interesting pattern. When I describe the argument in the abstract—that the way we make sense of the world can actually prevent us from understanding it—they nod their heads in vigorous agreement. “Yes,” they say, “I’ve always thought that people believe all sorts of silly things in order to make themselves feel like they understand things that in fact they don’t understand at all.” Yet when the very same argument calls into question some particular belief of their own, they invariably change their tune. “Everything you are saying about the pitfalls of common sense and intuition may be right,” they are in effect saying, “but it doesn’t undermine my own confidence in the particular beliefs I happen to hold.” It’s as if the failure of commonsense reasoning is only the failure of other people’s reasoning, not their own.

People, of course, make this sort of error all the time. Around 90 percent of Americans believe they are better-than-average drivers, and a similarly impossible number of people claim that they are happier, more popular, or more likely to succeed than the average person. In one study, an incredible 25 percent of respondents rated themselves in the top 1 percent in terms of leadership ability.7 This “illusory superiority” effect is so common and so well known that it even has a colloquial catchphrase—the Lake Wobegone effect, named for Prairie Home Companion host Garrison Keillor’s fictitious town where “all the children are above average.” It’s probably not surprising, therefore, that people are much more willing to believe that others have misguided beliefs about the world than that their own beliefs are misguided. Nevertheless, the uncomfortable reality is that what applies to “everyone” necessarily applies to us, too. That is, the fallacies embedded in our everyday thinking and explanations, which I will be discussing in more detail later, must apply to many of our own, possibly deeply held, beliefs.

None of this is to say that we should abandon all our beliefs and start over from scratch—only that we should hold them up to a spotlight and regard them with suspicion. For example, I do think that I’m an above-average driver—even though I know that statistically speaking, nearly half the people who think the same thing as I do are wrong. I just can’t help it. Knowing this, however, I can at least consider the possibility that I might be deluding myself, and so try to pay attention to when I make mistakes as well as when others do. Possibly I can begin to accept that not every altercation is necessarily the other guy’s fault, even if I’m still inclined to think it is. And perhaps I can learn from these experiences to determine what I should do differently as well as what others should be doing differently. Even after doing all this, I can’t be sure that I’m a better-than-average driver. But I can at least become a better driver.

In the same way, when we challenge our assumptions about the world—or even more important, when we realize we’re making an assumption that we didn’t even know we were making—we may or may not change our views. But even if we don’t, the exercise of challenging them should at least force us to notice our own stubbornness, which in turn should give us pause. Questioning our own beliefs in this way isn’t easy, but it is the first step in forming new, hopefully more accurate, beliefs. Because the chances that we’re already correct in everything we believe are essentially zero. In fact, the argument that Howard Becker was really making in the book that I read about all those years ago—an argument that was obviously lost on his reviewer, and at the time would have been lost on me, too—was that learning to think like a sociologist means learning to question precisely your instincts about how things work, and possibly to unlearn them altogether. So if reading this book only confirms what you already thought you knew about the world, then I apologize. As a sociologist, I will not have done my job.

PART ONE

COMMON SENSE

CHAPTER 1

The Myth of Common Sense

Every day in New York City five million people ride the subways. Starting from their homes throughout the boroughs of Manhattan, Brooklyn, Queens, and the Bronx, they pour themselves in through hundreds of stations, pack themselves into thousands of cars that barrel though the dark labyrinth of the Metropolitan Transportation Authority’s tunnel system, and then once again flood the platforms and stairwells—a subterranean river of humanity urgently seeking the nearest exit and the open air beyond. As anyone who has ever participated in this daily ritual can attest, the New York subway system is something between a miracle and nightmare, a Rube Goldberg contraption of machines, concrete, and people that in spite of innumerable breakdowns, inexplicable delays, and indecipherable public announcements, more or less gets everyone where they’re going, but not without exacting a certain amount of wear and tear on their psyche. Rush hour in particular verges on a citywide mosh pit—of tired workers, frazzled mothers, and shouting, shoving teenagers, all scrabbling over finite increments of space, time, and oxygen. It’s not the kind of place you go in search of the milk of human kindness. It’s not the kind of place where you’d expect a perfectly healthy, physically able young man to walk up to you and ask you for your seat.

And yet that’s precisely what happened one day in the early 1970s when a group of psychology students went out into the subway system on the suggestion of their teacher, the social psychologist Stanley Milgram. Milgram was already famous for his controversial “obedience” studies, conducted some years earlier at Yale, in which he had shown that ordinary people brought into a lab would apply what they thought were deadly electrical shocks to a human subject (really an actor who was pretending to be shocked) simply because they were told to do so by a white-coated researcher who claimed to be running an experiment on learning. The finding that otherwise respectable citizens could, under relatively unexceptional circumstances, perform what seemed like morally incomprehensible acts was deeply disturbing to many people—and the phrase “obedience to authority” has carried a negative connotation ever since.1

What people appreciated less, however, is that following the instructions of authority figures is, as a general rule, indispensible to the proper functioning of society. Imagine if students argued with their teachers, workers challenged their bosses, and drivers ignored traffic cops anytime they asked them to do something they didn’t like. The world would descend into chaos in about five minutes. Clearly there are moments when it’s appropriate to resist authority, and most people would agree that the situation Milgram created in the lab would qualify as such a moment. But what the experiment also illustrated was that the social order that we take for granted in everyday life is maintained in part by hidden rules that we don’t even realize exist until we try to break them.

Based on this experience, and having subsequently moved to New York, Milgram had begun to wonder if there was a similar “rule” about asking people for seats on the subway. Like the rule about obeying authority figures, this rule is never really articulated, nor would a typical rider be likely to mention it if asked to describe the rules of subway riding. And yet it exists, as Milgram’s students quickly discovered when they went about their little field experiment. Although more than half of the riders asked eventually surrendered their seats, many of them reacted angrily or demanded some explanation for the request. Everyone reacted with surprise, even amazement, and onlookers often made disparaging remarks. But more interesting than the response of the riders was that of the experimenters themselves, who found it extremely difficult to perform the experiment in the first place. Their reluctance was so great, in fact, that they had to go out in pairs, with one of them acting as moral support for the other. When the students reported their discomfort to Milgram, he scoffed at them. But when he tried to do the experiment himself, the simple act of walking up to a complete stranger and asking for his or her seat left him feeling physically nauseated. As trivial as it seemed, in other words, this rule was no more easily violated than the obedience-to-authority “rule” that Milgram had exposed years earlier.2

As it turns out, a big city like New York is full of these sorts of rules. On a crowded train, for example, it’s no big deal if you’re squeezed in against other people. But if someone stands right next to you when the train is empty, it’s actually kind of repellant. Whether it’s acknowledged or not, there’s clearly some rule that encourages us to spread out as much as we can in the available space, and violations of the rule can generate extreme discomfort. In the same way, imagine how uncomfortable you’d feel if someone got on your elevator and stood facing you instead of turning around to face the door. People face each other all the time in enclosed spaces, including on subway trains, and nobody thinks twice about it. But on an elevator it would feel completely weird, just as if the other person had violated some rule—even though it might not have occurred to you until that moment that any such rule existed. Or how about all the rules we follow for passing one another on the sidewalk, holding open doors, getting in line at the deli, acknowledging someone else’s right to a cab, making just the right amount of eye contact with drivers as you cross the street at a busy intersection, and generally being considerate of our fellow human beings while still asserting our own right to take up a certain amount of space and time?

No matter where we live, our lives are guided and shaped by unwritten rules—so many of them, in fact, that we couldn’t write them all down if we tried. Nevertheless, we expect reasonable people to know them all. Complicating matters, we also expect reasonable people to know which of the many rules that have been written down are OK to ignore. When I graduated from high school, for example, I joined the Navy and spent the next four years completing my officer training at the Australian Defence Force Academy. The academy back then was an intense place, replete with barking drill instructors, predawn push-ups, running around in the pouring rain with rifles, and of course lots and lots of rules. At first this new life seemed bizarrely complicated and confusing. However, we quickly learned that although some of the rules were important, to be ignored at your peril, many were enforced with something like a wink and a nod. Not that the punishments couldn’t be severe. You could easily get sentenced to seven days of marching around a parade ground for some minor infraction like being late to a meeting or having a wrinkled bedcover. But what you were supposed to understand (although of course you weren’t supposed to admit that you understood it) was that life at the academy was more like a game than real life. Sometimes you won, and sometimes you lost, and that was when you ended up on the drill square; but whatever happened, you weren’t supposed to take it personally. And sure enough, after about six months of acclimation, situations that would have terrified us on our arrival seemed entirely natural—it was now the rest of the world that seemed odd.

We’ve all had experiences like this. Maybe not quite as extreme as a military academy—which, twenty years later, sometimes strikes me as having happened in another life. But whether it’s learning to fit in at a new school, or learning the ropes in a new job, or learning to live in a foreign country, we’ve all had to learn to negotiate new environments that at first seem strange and intimidating and filled with rules that we don’t understand but eventually become familiar. Very often the formal rules—the ones that are written down—are less important than the informal rules, which just like the rule about subway seats may not even be articulated until we break them. Conversely, rules that we do know about may not be enforced, or may be enforced only sometimes depending on some other rule that we don’t know about. When you think about how complex these games of life can be, it seems kind of amazing that we’re capable of playing them at all. Yet in the way that young children learn a new language seemingly by osmosis, we learn to navigate even the most novel social environments more or less without even knowing that we’re doing it.

COMMON SENSE

The miraculous piece of human intelligence that enables us to solve these problems is what we call common sense. Common sense is so ordinary that we tend to notice it only when it’s missing, but it is absolutely essential to functioning in everyday life. Common sense is how we know what to wear when we go to work in the morning, how to behave on the street or the subway, and how to maintain harmonious relationships with our friends and coworkers. It tells us when to obey the rules, when to quietly ignore them, and when to stand up and challenge the rules themselves. It is the essence of social intelligence, and is also deeply embedded in our legal system, in political philosophy, and in professional training.

For something we refer to so often, however, common sense is surprisingly hard to pin down.3 Roughly speaking, it is the loosely organized set of facts, observations, experiences, insights, and pieces of received wisdom that each of us accumulates over a lifetime, in the course of encountering, dealing with, and learning from, everyday situations. Beyond that, however, it tends to resist easy classification. Some common-sense knowledge is very general in nature—what the American anthropologist Clifford Geertz called an “ancient tangle of received practices, accepted beliefs, habitual judgments, and untaught emotions.”4 But common sense can also refer to more specialized knowledge, as with the everyday working knowledge of a professional, such as a doctor, a lawyer, or an engineer, that develops over years of training and experience. In his address to the annual meeting of the American Sociological Society in Chicago in 1946, Carl Taylor, then president of the association, put it as well as anyone:

By common sense I mean the knowledge possessed by those who live in the midst and are a part of the social situations and processes which sociologists seek to understand. The term thus used may be synonymous with folk knowledge, or it may be the knowledge possessed by engineers, by the practical politicians, by those who gather and publish news, or by others who handle or work with and must interpret and predict the behavior or persons and groups.5

Taylor’s definition highlights two defining features of common sense that seem to differentiate it from other kinds of human knowledge, like science or mathematics. The first of these features is that unlike formal systems of knowledge, which are fundamentally theoretical, common sense is overwhelmingly practical, meaning that it is more concerned with providing answers to questions than in worrying about how it came by the answers. From the perspective of common sense, it is good enough to know that something is true, or that it is the way of things. One does not need to know why in order to benefit from the knowledge, and arguably one is better off not worrying about it too much. In contrast with theoretical knowledge, in other words, common sense does not reflect on the world, but instead attempts to deal with it simply “as it is.”6

The second feature that differentiates common sense from formal knowledge is that while the power of formal systems resides in their ability to organize their specific findings into logical categories described by general principles, the power of common sense lies in its ability to deal with every concrete situation on its own terms. For example, it is a matter of common sense that what we wear or do or say in front of our boss will be different from how we behave in front of our friends, our parents, our parents’ friends, or our friends’ parents. But whereas a formal system of knowledge would try to derive the appropriate behavior in all these situations from a single, more general “law,” common sense just “knows” what the appropriate thing to do is in any particular situation, without knowing how it knows it.7 It is largely for this reason, in fact, that commonsense knowledge has proven so hard to replicate in computers—because, in contrast with theoretical knowledge, it requires a relatively large number of rules to deal with even a small number of special cases. Let’s say, for example, that you wanted to program a robot to navigate the subway. It seems like a relatively simple task. But as you would quickly discover, even a single component of this task such as the “rule” against asking for another person’s subway seat turns out to depend on a complex variety of other rules—about seating arrangements on subways in particular, about polite behavior in public in general, about life in crowded cities, and about general-purpose norms of courteousness, sharing, fairness, and ownership—that at first glance seem to have little to do with the rule in question.

Attempts to formalize commonsense knowledge have all encountered versions of this problem—that in order to teach a robot to imitate even a limited range of human behavior, you would have to, in a sense, teach it everything about the world. Short of that, the endless subtle distinctions between the things that matter, the things that are supposed to matter but don’t, and the things that may or may not matter depending on other things, would always eventually trip up even the most sophisticated robot. As soon as it encountered a situation that was slightly different from those you had programmed it to handle, it would have no idea how to behave. It would stick out like a sore thumb. It would always be screwing up.8

People who lack common sense are a bit like the hapless robot in that they never seem to understand what it is that they should be paying attention to, and they never seem to understand what it is that they don’t understand. And for exactly the same reason that programming robots is hard, it’s surprisingly hard to explain to someone lacking in common sense what it is that they’re doing wrong. You can take them back through various examples of when they said or did the wrong thing, and perhaps they’ll be able to avoid making exactly those errors again. But as soon as anything is different, they’re effectively back to square one. We had a few cadets like that at the academy: otherwise perfectly intelligent, competent people who just couldn’t seem to figure out how to play the game. Everyone knew who they were, and everyone could see that they just didn’t get it. But because it wasn’t exactly clear what it was that they didn’t get, we were unable to help them. Bewildered and overwhelmed, most of them eventually left.

NOT COMMON AT ALL

As remarkable as it is, common sense exhibits some mysterious quirks, one of the most striking of which is how much it varies over time, and across cultures. Several years ago, for example, an enterprising group of economists and anthropologists set out to test how different cultures play a particular kind of game, called an ultimatum game. The game goes something like this: First, pick two people and give one of them $100. That person then has to propose a split of the money between himself and the other player, ranging from offering them the whole amount to nothing at all. The other player then gets to accept the deal or reject it. If the second player accepts the deal, they get what they were offered and both players go on their merry way. But if they reject the offer, neither player gets anything; hence the “ultimatum.”

In hundreds of these experiments conducted in industrialized societies, researchers had already demonstrated that most players propose a fifty-fifty split, and offers of less than $30 are typically rejected. Economists find this behavior surprising because it conflicts with their standard notion of economic rationality. Even a single dollar, the reasoning goes, is better than nothing at all, so from a strictly rational perspective, recipients ought to accept any offer above zero. And knowing this, rational “proposers” ought to offer the least they can get away with—namely, one dollar. Of course, a moment’s thought quickly suggests why people play the way they do—namely that it doesn’t seem fair to exploit a situation just because you can. Recipients being offered less than a third therefore feel taken advantage of and so opt to walk away from even a substantial sum of money in order to teach miserly proposers a lesson. And anticipating this response, proposers tend to offer what they assume the recipient will consider a fair split.

If your reaction to this breakthrough insight is that economists need to get out a little more, then you’re not alone. If anything seems like common sense, it’s that people care about fairness as well as money—sometimes even more so. But when the experimenters replicated the game in fifteen small-scale preindustrial societies across five continents, they found that people in different societies have very different ideas about what counts as fair. At one extreme, the Machiguenga tribe of Peru tended to offer only about a quarter of the total amount, and virtually no offers were refused. At the other extreme, the Au and Gnau tribes of Papua New Guinea tended to make offers that were even better than fifty-fifty, but surprisingly these “hyperfair” offers tended to get rejected just as frequently as unfair offers.9

What explains these differences? As it turns out, the Au and Gnau tribes had long-established customs of gift exchange, according to which receiving a gift obligates the receiver to reciprocate at some point in the future. Because there was no equivalent of the ultimatum game in the Au or Gnau societies, they simply “mapped” the unfamiliar interaction onto the most similar social exchange they could think of—which happened to be gift exchange—and responded accordingly. Thus what might have seemed like free money to a Western participant looked to an Au or Gnau participant very much like an unwanted obligation. The Machiguenga, by contrast, live in a society in which the only relationship bonds that carry any expectation of loyalty are with immediate family members. When playing the ultimatum game with a stranger, therefore, Machiguenga participants—again mapping the unfamiliar onto the familiar—saw little obligation to make fair offers, and experienced very little of the resentment that would well up in a Western player upon being presented with a split that was patently unequal. To them, even low offers were seen as a good deal.

Once you understand these features of Au, Gnau, and Machiguenga cultures, their puzzling behavior starts to seem entirely reasonable—commonsense even. And that’s exactly what it was. Just as we reflexively regard fairness and reciprocity as commonsense principles in our world that should be respected in general, and should be defended when violated without good reason, so the people of the fifteen pre industrial societies have their own implicit set of understandings about how the world is supposed to work. Those understandings might be different from ours. But once they have been accepted, their commonsense logic works in exactly the same way as ours does. It is simply what any reasonable person would do if they had grown up in that culture.

What these results reveal is that common sense is “common” only to the extent that two people share sufficiently similar social and cultural experiences. Common sense, in other words, depends on what the sociologist Harry Collins calls collective tacit knowledge, meaning that it is encoded in the social norms, customs, and practices of the world.10 According to Collins, the acquisition of this type of knowledge can be learned only by participating in society itself—and that’s why it is so hard to teach to machines. But it also means that even among humans, what seems reasonable to one might seem curious, bizarre, or even repugnant to another. For example, as Clifford Geertz, the anthropologist, has described, the treatment of hermaphroditic children has varied dramatically across different times and cultures. The Romans abhorred and killed them; the Greeks tolerated them; the Navajo revered them; and the east African Pokot tribe regarded them simply as “mistakes,” to be kept around or discarded in the same way they might keep or throw out a flawed pot.11 Likewise, practices including human slavery, sacrifice, cannibalism, foot binding, and female genital mutilation that are reviled in most contemporary cultures have all been (and in some cases, still are) considered entirely legitimate in different times and places.

Another important consequence of the socially embedded nature of common sense is that disagreements over matters of common sense can be surprisingly difficult to resolve. For example, it may seem remarkable to people who have grown up with the impression that New York is a crime-ridden cess-pool, or at the very least a cold, hard-edged city full of people you can’t trust, that, according to a recent news story, there is a small cadre of Manhattan residents who don’t lock their doors. As the article makes clear, most people in the city think that the “no lock people” are crazy. As one woman said, “I live in a high-rise with a doorman, I’ve been there fifteen years, and I’ve never heard of a burglary in the building. But that has absolutely nothing to do with it—it’s common sense [to lock your door].” Yet the only thing that seems shocking to the people who don’t lock their doors is that anyone else would be shocked by it.12

What’s curious about this story is that the language of the people involved almost precisely mirrors the experiences of Geertz, who noted in his study of witchcraft in Java that “when the whole family of a Javanese boy tells me that the reason he has fallen out of a tree and broken his leg is that the spirit of his deceased grandfather pushed him out because some ritual duty toward the grandfather has been inadvertently overlooked, that, so far as they are concerned, is the beginning, the middle, and the end of the matter: it is precisely what they think has occurred, it is all they think has occurred, and they are puzzled only at my puzzlement at their lack of puzzlement.” Disagreements over matters of common sense, in other words, are hard to resolve because it’s unclear to either side on what grounds one can even conduct a reasonable argument. Whether the issue is a Western anthropologist discussing witchcraft with pre industrial tribes in Indonesia, New Yorkers disagreeing about door locks, or the NRA disagreeing with the Brady Campaign over the sorts of guns that Americans ought to be able to buy, whatever it is that people believe to be a matter of common sense, they believe it with absolute certainty. They are puzzled only at the fact that others disagree.13

SOME RESERVATIONS

That what is self-evident to one person can be seen as silly by another should give us pause about the reliability of common sense as a basis for understanding the world. How can we be confident that what we believe is right when someone else feels equally strongly that it’s wrong—especially when we can’t articulate why we think we’re right in the first place? Of course, we can always write them off as crazy or ignorant or something and therefore not worth paying attention to. But once you go down that road, it gets increasingly hard to account for why we ourselves believe what we do. Consider, for example, that since 1996 support among the general public for allowing same-sex couples to marry has almost doubled, from 25 percent to 45 percent.14 Presumably those of us who changed our minds over this period do not think that we were crazy fourteen years ago, but we obviously think that we were wrong. So if something that seemed so obvious turned out to be wrong, what else that we believe to be self-evident now will seem wrong to us in the future?

Once we start to examine our own beliefs, in fact, it becomes increasingly unclear even how the various beliefs we espouse at any given time fit together. Most people, for example, consider their own views about politics to be derived from a single coherent worldview: “I’m a moderate liberal” or “I’m a diehard conservative,” and so on. If that were true, however, then one would expect that people who identify as liberals would tend to espouse the “liberal” perspective on most matters, and that conservatives would espouse a consistently different view. Yet research finds that regardless of whether people identify themselves as liberals or conservatives, what they think about any one issue, like, say, abortion, has relatively little relation to what they believe about other issues, such as the death penalty or illegal immigration. In other words, we have the impression that our particular beliefs are all derived from some overarching philosophy, but the reality is that we arrive at them quite independently, and often haphazardly.15

The same difficulty of reconciling what, individually, appear to be self-evident beliefs shows up even more clearly in the aphorisms that we invoke to make sense of the world. As sociologists are fond of pointing out, many of these aphorisms appear to be direct contradictions of each other. Birds of a feather flock together, but opposites attract. Absence indeed makes the heart grow fonder, but out of sight is out of mind. Look before you leap, but he who hesitates is lost. Of course, it is not necessarily the case that these beliefs are contradictory—because we invoke different aphorisms in different circumstances. But because we never specify the conditions under which one aphorism applies versus another, we have no way of describing what it is that we really think or why we think it. Common sense, in other words, is not so much a worldview as a grab bag of logically inconsistent, often contradictory beliefs, each of which seems right at the time but carries no guarantee of being right any other time.

THE MISUSE OF COMMON SENSE

The fragmented, inconsistent, and even self-contradictory nature of common sense does not generally present a problem in our everyday lives. The reason is that everyday life is effectively broken up into small problems, grounded in very specific contexts that we can solve more or less independently of one another. Under these circumstances, being able to connect our thought processes in a logical manner isn’t really the point. It doesn’t really matter that absence makes the heart grow fonder in one situation, and that out of sight is out of mind in the next. In any given situation we know the point we’re trying to make, or the decision we want to support, and we choose the appropriate piece of commonsense wisdom to apply to it. If we had to explain how all our explanations, attitudes, and commonsense beliefs fit together, we would encounter all kinds of inconsistencies and contradictions. But because our experience of life rarely forces us to perform this task, it doesn’t really matter how difficult it would be.

Where it does start to matter, however, is when we use common sense to solve problems that are not grounded in the immediate here and now of everyday life—problems that involve anticipating or managing the behavior of large numbers of people, in situations that are distant from us either in time or space. This may sound like an unlikely thing to do, but in fact we do it all the time. Whenever we read a newspaper and try to understand events playing out in some foreign country—the Israel-Palestine conflict, the unfolding insurgency in Iraq, or the seemingly endless conflict in Afghanistan—we are implicitly using our commonsense reasoning to infer the causes and explanations of the events we’re reading about. Whenever we form an opinion about financial reform or healthcare policy, we are implicitly using our commonsense reasoning to speculate about how different rules and incentives will affect the various parties’ behavior. And whenever we argue about politics or economics or the law, we are implicitly using our commonsense reasoning to reach conclusions about how society will be affected by whatever policy or proposal is being debated.

In none of these cases are we using our common sense to reason about how we should behave in the here and now. Rather, we are using it to reason about how other people behaved—or will behave—in circumstances about which we have at best an incomplete understanding. At some level we understand that the world is complicated, and that everything is somehow connected to everything else. But when we read some story about reforming the healthcare system, or about banker bonuses, or about the Israel-Palestine conflict, we don’t try to understand how all these different problems fit together. We just focus on the one little piece of the huge underlying tapestry of the world that’s being presented to us at that moment, and form our opinion accordingly. In this way, we can flip through the newspaper while drinking our morning cup of coffee and develop twenty different opinions about twenty different topics without breaking a sweat. It’s all just common sense.

It may not matter much, of course, what conclusions ordinary citizens reach about the state of the world in the privacy of their own homes, based on what they’re reading in the newspaper or arguing about with their friends. So it may not matter much that the way we reason about the problems of the world is poorly suited to the nature of the problems themselves. But ordinary citizens are not the only ones who apply commonsense reasoning to social problems. When policy makers sit down, say, to design some scheme to alleviate poverty, they invariably rely on their own commonsense ideas about why it is that poor people are poor, and therefore how best to help them. As with all commonsense explanations, it is likely that everyone will have his or her own views, and that these views will be logically inconsistent or even contradictory. Some may believe that people are poor because they lack certain necessary values of hard work and thrift, while others may think they are genetically inferior, and others still may attribute their lack of wealth to lack of opportunities, inferior systems of social support, or other environmental factors. All these beliefs will lead to different proposed solutions, not all of which can be right. Yet policy makers empowered to enact sweeping plans that will affect thousands or millions of people are no less tempted to trust their intuition about the causes of poverty than ordinary citizens reading the newspaper.

A quick look at history suggests that when common sense is used for purposes beyond the everyday, it can fail spectacularly. As the political scientist James Scott writes in Seeing Like a State, the late nineteenth and early twentieth centuries were characterized by pervasive optimism among engineers, architects, scientists, and government technocrats that the problems of society could be solved in the same way that the problems of science and engineering had been solved during the Enlightenment and the industrial revolution. According to these “high modernists,” the design of cities, the management of natural resources, even the business of running an entire economy were all within the scope of “scientific” planning. As one of the undisputed high priests of modernism, the architect Le Corbusier, wrote in 1923, “the plan is generator; without it poverty, disorder, willfulness reign supreme.”16

Naturally, the high modernists didn’t describe what they were doing as an exercise in using their common sense, preferring instead to clothe their ambitions in the language of science. But as Scott points out, this scientific aura was a mirage. In reality there was no science of planning—just the opinions of individual planners who relied on their intuition to speculate about how their plans would play out in the real world. No one doubts that men like Le Corbusier were brilliant and original thinkers. Nevertheless, the outcomes of their plans, like Soviet collectivization or Le Corbusier’s Brasilia, were often disastrous; and some of them, like the social engineering of Nazism or apartheid in South Africa, are now regarded among the great evils of the twentieth century. Moreover, even when these plans did succeed, they often did so in spite of themselves, as individuals on the ground figured out ways to create a reasonable outcome by ignoring, circumventing, or even undermining the plan itself.17

Looking back, it may seem as if the failures of high modernism—whether centrally planned economies or centrally designed cities—are a thing of the past, a product of a naïve and simplistic belief in science that we have since outgrown. Yet politicians, bureaucrats, architects, and regulators continue to make essentially the same mistake all the time. As the economist William Easterly has argued, the foreign aid community has been dominated for the past fifty years by large, bureaucratic organizations that are in turn run by powerful individuals whose ideas about what should and should not work inevitably play a large role in determining how resources will be devoted. Just as with the high modernists before them, these “planners,” as Easterly calls them, are well-meaning and intelligent people who are often passionately devoted to the task of helping the people of the developing world. Yet in spite of the trillions of dollars of aid that planners have devoted to economic development, there is shockingly little evidence that the recipients are better off for it.18

Closer to home, and over roughly the same period of time, urban planners in the United States have repeatedly set out to “solve” the problem of urban poverty and have repeatedly failed. As the journalist and urban activist Jane Jacobs put it fifty years ago, “There is a wistful myth that if only we had enough money to spend—the figure is usually put at a hundred billion dollars—we could wipe out all our slums in ten years. . . . But look what we have built with the first several billions: Low-income projects that have become worse centers of delinquency, vandalism and general social hopelessness than the slums they were supposed to replace.”19 It is ironic that around the same time that Jacobs reached this conclusion, work began on the Robert Taylor Homes in Chicago, the largest public housing project ever built. And sure enough, as the sociologist Sudhir Venkatesh describes in American Project, what started out as a high-minded and carefully thought-out plan to help inner-city, largely African American families rise up into the middle class became a debacle of dilapidated buildings, overcrowded apartments and playgrounds, concentrated poverty, and eventually gang violence.20