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Thinking, Fast and Slow is a best-selling[1] book published in 2011 by Nobel Memorial Prize in Economic Sciences laureate Daniel Kahneman. It was the 2012 winner of the National Academies Communication Award for best creative work that helps the public understanding of topics in behavioral science, engineering and medicine.[2]

The book summarizes research that Kahneman conducted over decades, often in collaboration with Amos Tversky.[3][4] It covers all three phases of his career: his early days working on cognitive biases, his work on prospect theory, and his later work on happiness.[not verified in body]

The central thesis is a dichotomy between two modes of thought: "System 1" is fast, instinctive and emotional; "System 2" is slower, more deliberative, and more logical. The book delineates cognitive biases associated with each type of thinking, starting with Kahneman's own research on loss aversion. From framing choices to people's tendency to replace a difficult question with one which is easy to answer, the book highlights several decades of academic research to suggest that people place too much confidence in human judgment.[not verified in body]

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In the book's first section, Kahneman describes two different ways the brain forms thoughts:

System 1: (Fast, automatic, frequent, emotional, stereotypic, unconscious) vs System 2: (Slow, effortful, infrequent, logical, calculating, conscious).

The second section offers explanations for why humans struggle to think statistically . . .documenting a variety of situations in which we either arrive at binary decisions or fail to precisely associate reasonable probabilities with outcomes. Kahneman explains this phenomenon using the theory of heuristics.

• Anchoring: The "anchoring effect" names our tendency to be influenced by irrelevant numbers. Shown higher/lower numbers, experimental subjects gave higher/lower responses.
  
• Availability: The availability heuristic is a mental shortcut that occurs when people make judgments about the probability of events on the basis of how easy it is to think of examples.
  
• Substitution: System 1 is prone to substituting a difficult question with a simpler one.
  
• Optimism and Loss Aversion: Kahneman writes of a "pervasive optimistic bias", which "may well be the most significant of the cognitive biases." This bias generates the illusion of control, that we have substantial control of our lives.
  
• Framing: the context in which choices are presented.
  
• Overconfidence: this section of the book is dedicated to the undue confidence in what the mind believes it knows.
  

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Kahneman developed prospect theory, the basis for his Nobel prize, to account for experimental errors he noticed in Daniel Bernoulli's traditional utility theory.[11] According to Kahneman, Utility Theory makes logical assumptions of economic rationality that do not reflect people's actual choices, and does not take into account cognitive biases.

One example is that people are loss-averse: they are more likely to act to avert a loss than to achieve a gain. Another example is that the value people place on a change in probability (e.g., of winning something) depends on the reference point: people appear to place greater value on a change from 0% to 10% (going from impossibility to possibility) than from, say, 45% to 55%, and they place the greatest value of all on a change from 90% to 100% (going from possibility to certainty). This occurs despite the fact that under traditional utility theory all three changes give the same increase in utility. Consistent with loss-aversion, the order of the first and third of those is reversed when the event is presented as losing rather than winning something: there, the greatest value is placed on eliminating the probability of a loss to 0.

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Daniel Kahneman (/ˈkɑːnəmən/; Hebrew: דניאל כהנמן‎; born March 5, 1934) is an Israeli-American psychologist and economist notable for his work on the psychology of judgment and decision-making, as well as behavioral economics, for which he was awarded the 2002 Nobel Memorial Prize in Economic Sciences (shared with Vernon L. Smith). His empirical findings challenge the assumption of human rationality prevailing in modern economic theory.

With Amos Tversky and others, Kahneman established a cognitive basis for common human errors that arise from heuristics and biases (Kahneman & Tversky, 1973; Kahneman, Slovic & Tversky, 1982; Tversky & Kahneman, 1974), and developed prospect theory (Kahneman & Tversky, 1979).

In 2011, he was named by Foreign Policy magazine to its list of top global thinkers.[2] In the same year, his book Thinking, Fast and Slow, which summarizes much of his research, was published and became a best seller.[3]

He is professor emeritus of psychology and public affairs at Princeton University's Woodrow Wilson School. Kahneman is a founding partner of TGG Group, a business and philanthropy consulting company. He was married to cognitive psychologist and Royal Society Fellow Anne Treisman, who died on February 9, 2018.[4]

In 2015, The Economist listed him as the seventh most influential economist in the world.[5]

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The Irony Effect: How the scientist who founded the science of mistakes ended up mistaken.

Danny Kahneman’s love affair with Amos Tversky began in the spring of 1969, when his dazzling and clever colleague, also a professor of psychology at Hebrew University in Jerusalem, came to give a talk to Kahneman’s graduate seminar. Tversky told the students about a new study being done by researchers in Michigan on how regular people tend to think about statistics. The work suggested that we all have a natural grasp of probability, Tversky said. We’re all inclined to be rational.

“Brilliant talk,” said Kahneman when Tversky finished, “but I don’t believe a word of it.” He had strong reasons to be skeptical. For years, his own research had been derailed by faulty intuitions about how to use statistics. Even though Kahneman was highly trained in research methods, he’d kept on falling victim to the same mistake: His sample sizes were too small.

Kahneman also knew that he was not the only scholar screwing up. He’d seen a recent paper showing that the problem was ubiquitous: Even studies in the leading journals of psychology, performed by scientists who specialized in quantitative research, were underpowered as a rule. And now Tversky meant to argue that everyone’s a natural statistician?

. . . .

Kahneman had been terrified to write the book; according to Lewis, he worried that it would destroy his reputation. (Like a good behavioral economist, he even paid his colleagues to read the manuscript and provide anonymous advice about whether to abandon it.) To his surprise, Thinking, Fast and Slow became a huge success—a critically acclaimed, best-selling, award-winning culmination of his long career.

Within a few months of its publication, though, the study of psychology went into a state of crisis. Many of the findings that Kahneman had cited in the book—and lots of others, too—suddenly appeared to be quite fragile, maybe even spurious. In a section on “The Marvels of Priming,” for example, Kahneman had described the way that “primed” ideas spread across the mind like ripples on a pond, and that “the mapping of these ripples is now one of the most exciting pursuits in psychological research.” But shortly after he finished the book, the enterprise of social-priming research fell into scandal and uncertainty. An influential scholar in the field was outed as a fraud. A bedrock finding in the field—drawn from a study that Kahneman called an “instant classic”—crumbled under scrutiny.

. . . .

The replication crisis in psychology does not extend to every line of inquiry, and just a portion of the work described in Thinking, Fast and Slow has been cast in shadows. Kahneman and Tversky’s own research, for example, turns out to be resilient. Large-scale efforts to recreate their classic findings have so far been successful. One bias they discovered—people’s tendency to overvalue the first piece of information that they get, in what is known as the “anchoring effect”—not only passed a replication test, but turned out to be much stronger than Kahneman and Tversky thought.

Still, entire chapters of Kahneman’s book may need to be rewritten. The psychologist Uli Schimmack has devised a statistical measure called the R-index to estimate the trustworthiness of a given body of research based on its reported sample sizes and effects. (It’s like a “doping test for science,” Schimmack says.) He recently applied this measure to the studies cited in each of 11 different chapters from Thinking, Fast and Slow, then assigned letter grades to each result. (The book has 38 chapters total.) A couple of the chapters came out looking very good, with R-index scores of 93 and 99—worthy of an A-plus grade from Schimmack for their rigor. But five other chapters, including the one on social priming, ended up with scores of less than 40—what Schimmack called an F. Taken all together, the chapters Schimmack looked at earned an average grade of C-minus.


How could Kahneman, of all people—a man so brilliant at describing weakness, so canny in his doubts, so quick to cut through bullshit—have signed his name to all this suspect science? Had his thinking gotten credulous, as Tversky had suggested in that letter written in the midst of their divorce? Or had he succumbed to normal human error, like the one that he discovered in the 1960s, right around the time he and Tversky met?

No one is a natural statistician, he’d argued at the time. Even scientists make mistakes. As usual, when it came to being wrong, Kahneman was right.

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Schimmack and Brunner (2015) developed an alternative method for the estimation of replicability. This method takes into account that power can vary across studies. It also provides 95% confidence intervals for the replicability estimate. The results of this method are presented in the Figure above. The replicability estimate is similar to the R-Index, with 14% replicability. However, due to the small set of studies, the 95% confidence interval is wide and includes values above 50%. This does not mean that we can trust the published results, but it does suggest that some of the published results might be replicable in larger replication studies with more power to detect small effects. At the same time, the graph shows clear evidence for a selection effect. That is, published studies in these articles do not provide a representative picture of all the studies that were conducted. The powergraph shows that there should have been a lot more non-significant results than were reported in the published articles. The selective reporting of studies that worked is at the core of the replicability crisis in social psychology (Sterling, 1959, Sterling et al., 1995; Schimmack, 2012). To clean up their act and to regain trust in published results, social psychologists have to conduct studies with larger samples that have more than 50% power (Tversky & Kahneman, 1971) and they have to stop reporting only significant results. We can only hope that social psychologists will learn from the train wreck of social priming research and improve their research practices.

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What the blog gets absolutely right is that I placed too much faith in underpowered studies. As pointed out in the blog, and earlier by Andrew Gelman, there is a special irony in my mistake because the first paper that Amos Tversky and I published was about the belief in the “law of small numbers,” which allows researchers to trust the results of underpowered studies with unreasonably small samples. We also cited Overall (1969) for showing “that the prevalence of studies deficient in statistical power is not only wasteful but actually pernicious: it results in a large proportion of invalid rejections of the null hypothesis among published results.” Our article was written in 1969 and published in 1971, but I failed to internalize its message.

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A bit over four years ago I wrote a glowing review of Daniel Kahneman’s Thinking, Fast and Slow. I described it as a “magnificent book” and “one of the best books I have read”. I praised the way Kahneman threaded his story around the System 1 / System 2 dichotomy, and the coherence provided by prospect theory.

What a difference four years makes. I will still describe Thinking, Fast and Slow as an excellent book – possibly the best behavioural science book available. But during that time a combination of my learning path and additional research in the behavioural sciences has led me to see Thinking, Fast and Slow as a book with many flaws.

First, there is the list of studies that simply haven’t held up through the “replication crisis” of the last few years. The first substantive chapter of Thinking, Fast and Slow is on priming, so many of these studies are right up the front. These include the Florida effect, money priming, the idea that making a test harder to read can increase test results, and ego depletion (I touch on each of these in my recent talk at the Sydney Behavioural Economics and Behavioural Science Meetup).

cebrail posted:

I wanted to read this a few weeks ago but I didn't get past page 70 or so.
Is the entire book written like a self help book where every little facet of his theory is explained ten times in a row with five almost identical examples? If that's the reason it has 500 pages I definitely won't read all of them.

anilEhilated posted:

It's basically psychology aimed at the Average Joe and the style reflects that, yeah. That being said, it's definitely way above self-help stuff. I'd say it's worth giving a chance.

pangstrom posted:

Somebody might rise to that challenge and comb through each and every mention, but if you want a HEURISTIC: if it is "cool" social priming that might get a blurb in mainstream journalism (say, a 60 second science podcast), it doesn't replicate.

Apsyrtes posted:

I read this about 6 years ago - it's amazing. No self-help here, it presents the evidence based work of a Nobel Prize winner - and tells you nothing about what to do with that information.

I rarely ever re-read a book. I've been really wanting to re-read this one, but have always put that off in favour of making progress on my Want to Read list... I picked it up last night and started re-reading thanks to BOTM.

A human heart posted:

the nobel prize in economics isn't even a real nobel prize.

A human heart posted:

the nobel prize in economics isn't even a real nobel prize.

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To appreciate the autonomy of System 1, as well as the distinction between impressions and beliefs, take a good look at figure 3.

This picture is unremarkable: two horizontal lines of different lengths, with fins appended, pointing in different directions. The bottom line is obviously longer than the one above it. That is what we all see, and we naturally believe what we see. If you have already encountered this image, however, you recognize it as the famous Müller-Lyer illusion. As you can easily confirm by measuring them with a ruler, the horizontal lines are in fact identical in length.



Figure 3

Now that you have measured the lines, you—your System 2, the conscious being you call “I”—have a new belief: you know that the lines are equally long. If asked about their length, you will say what you know. But you still see the bottom line as longer. You have chosen to believe the measurement, but you cannot prevent System 1 from doing its thing; you cannot decide to see the lines as equal, although you know they are. To resist the illusion, there is only one thing you can do: you must learn to mistrust your impressions of the length of lines when fins are attached to them. To implement that rule, you must be able to recognize the illusory pattern and recall what you know about it. If you can do this, you will never again be fooled by the Müller-Lyer illusion. But you will still see one line as longer than the other.

Not all illusions are visual. There are illusions of thought, which we call cognitive illusions. As a graduate student, I attended some courses on the art and science of psychotherapy. During one of these lectures, our teacher imparted a morsel of clinical wisdom. This is what he told us: “You will from time to time meet a patient who shares a disturbing tale of multiple mistakes in his previous treatment. He has been seen by several clinicians, and all failed him. The patient can lucidly describe how his therapists misunderstood him, but he has quickly perceived that you are different. You share the same feeling, are convinced that you understand him, and will be able to help.” At this point my teacher raised his voice as he said, “Do not even think of taking on this patient! Throw him out of the office! He is most likely a psychopath and you will not be able to help him.”

Many years later I learned that the teacher had warned us against psychopathic charm, and the leading authority in the study of psychopathy confirmed that the teacher’s advice was sound. The analogy to the Müller-Lyer illusion is close. What we were being taught was not how to feel about that patient. Our teacher took it for granted that the sympathy we would feel for the patient would not be under our control; it would arise from System 1. Furthermore, we were not being taught to be generally suspicious of our feelings about patients. We were told that a strong attraction to a patient with a repeated history of failed treatment is a danger sign—like the fins on the parallel lines. It is an illusion—a cognitive illusion—and I (System 2) was taught how to recognize it and advised not to believe it or act on it.

The question that is most often asked about cognitive illusions is whether they can be overcome. The message of these examples is not encouraging. Because System 1 operates automatically and cannot be turned off at will, errors of intuitive thought are often difficult to prevent. Biases cannot always be avoided, because System 2 may have no clue to the error. Even when cues to likely errors are available, errors can be prevented only by the enhanced monitoring and effortful activity of System 2. As a way to live your life, however, continuous vigilance is not necessarily good, and it is certainly impractical. Constantly questioning our own thinking would be impossibly tedious, and System 2 is much too slow and inefficient to serve as a substitute for System 1 in making routine decisions. The best we can do is a compromise: learn to recognize situations in which mistakes are likely and try harder to avoid significant mistakes when the stakes are high. The premise of this book is that it is easier to recognize other people’s mistakes than our own.

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Research has shown that perception of the Müller-Lyer illusion can vary. Around the turn of the 20th century, W. H. R. Rivers noted that indigenous people of the Australian Murray Island were less susceptible to the Müller-Lyer illusion than were Europeans.[4] Rivers suggested that this difference may be because Europeans live in more rectilinear environments than the islanders. Similar results were also observed by John W. Berry in his work on Inuit, urban Scots, and the Temne people in the 1960s.[5]

In 1963, Segall, Campbell and Herskovitz compared susceptibility to four different visual illusions in three population samples of Caucasians, twelve of Africans, and one from the Philippines. For the Müller-Lyer illusion, the mean fractional misperception of the length of the line segments varied from 1.4% to 20.3%. The three European-derived samples were the three most susceptible samples, while the San foragers of the Kalahari desert were the least susceptible.[6]

In 1965, following a debate between Donald T. Campbell and Melville J. Herskovits on whether culture can influence such basic aspects of perception such as the length of a line, they suggested that their student Marshall Segall investigate the problem. In their definitive paper of 1966, they investigated seventeen cultures and showed that people in different cultures differ substantially on how they experience the Müller-Lyer stimuli. They wrote that "European and American city dwellers have a much higher percentage of rectangularity in their environments than non-Europeans and so are more susceptible to that illusion."[7]

They also used the word "carpentered" for the environments that Europeans mostly live in - characterized by straight lines, right angles, and square corners.

These conclusions were challenged in later work by Gustav Jahoda, who compared members of an African tribe living in a traditional rural environment with members of same group living in African cities. Here, no significant difference in susceptibility to the M-L illusion was found. Subsequent work by Jahoda suggested that retinal pigmentation may have a role in the differing perceptions on this illusion,[8] and this was verified later by Pollack (1970). It is believed now that not "carpenteredness", but the density of pigmentation in the eye is related to susceptibility to the M-L illusion. Dark-skinned people often have denser eye pigmentation.[9]

A later study was conducted in 1978 by Ahluwalia on children and young adults from Zambia. Subjects from rural areas were compared with subjects from urban areas. The subjects from urban areas were shown to be considerably more susceptible to the illusion, as were younger subjects.[10] While this by no means confirms the carpentered world hypothesis as such, it provides evidence that differences in the environment can create differences in the perception of the Müller-Lyer illusion, even within a given culture. Experiments have been reported suggesting that pigeons perceive the standard Müller-Lyer illusion, but not the reversed.[11] Experiments on parrots have also been reported with similar results.[12]

Hieronymous Alloy posted:

killer crane posted:

I keep wondering, as I read through this, what results are contingent on culture, and which are universally human responses. Like the experiments on priming with images of money; is it specifically money? Are there other objects that give the same responses? Is there some people, cultures, condition that priming isn't as effective?

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A disturbing demonstration of depletion effects in judgment was recently reported in the Proceedings of the National Academy of Sciences. The unwitting participants in the study were eight parole judges in Israel. They spend entire days reviewing applications for parole. The cases are presented in random order, and the judges spend little time on each one, an average of 6 minutes. (The default decision is denial of parole; only 35% of requests are approved. The exact time of each decision is recorded, and the times of the judges’ three food breaks—morning break, lunch, and afternoon break—during the day are recorded as well.) The authors of the study plotted the proportion of approved requests against the time since the last food break. The proportion spikes after each meal, when about 65% of requests are granted. During the two hours or so until the judges’ next feeding, the approval rate drops steadily, to about zero just before the meal. As you might expect, this is an unwelcome result and the authors carefully checked many alternative explanations. The best possible account of the data provides bad news: tired and hungry judges tend to fall back on the easier default position of denying requests for parole. Both fatigue and hunger probably play a role.

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Glöckner’s analysis doesn’t prove that extraneous factors weren’t influencing the judges, but he shows how the same effect could be produced by entirely rational judges interacting with the protocols required by the legal system.

The main analysis works like this: we know that favourable rulings take longer than unfavourable ones (~7 mins vs ~5 mins), and we assume that judges are able to guess how long a case will take to rule on before they begin it (from clues like the thickness of the file, the types of request made, the representation the prisoner has and so on). Finally, we assume judges have a time limit in mind for each of the three sessions of the day, and will avoid starting cases which they estimate will overrun the time limit for the current session.

It turns out that this kind of rational time-management is sufficient to generate the drops in favourable outcomes. How this occurs isn’t straightforward and interacts with a quirk of original author’s data presentation (specifically their graph shows the order number of cases when the number of cases in each session varied day to day – so, for example, it shows that the 12th case after a break is least likely to be judged favourably, but there wasn’t always a 12 case in each session. So sessions in which there were more unfavourable cases were more likely to contribute to this data point).

This story of claim and counter-claim shows why psychologists prefer experiments, since only then can you truly isolate causal explanations (if you are a judge and willing to go without lunch please get in touch). Also, it shows the benefit of simulations for extending the horizons of our intuition. Glöckner’s achievement is to show in detail how some reasonable assumptions – including that of a rational judge – can generate a pattern which hitherto seemed only explainable by the influence of an irrelevant factor on the judges decisions. This doesn’t settle the matter, but it does mean we can’t be so confident that this graph shows what it is often claimed to show. The judges decisions may not be irrational after all, and the timing of the judges meal breaks may not be influencing parole decision outcome.

Hieronymous Alloy posted:

If this study is valid, then Legal decisions aren't governed by laws or reasoning; they're governed by whether or not the judge has eaten or napped within the past few hours!

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The Focusing Illusion

We can infer from the speed with which people respond to questions about their life, and from the effects of current mood on their responses, that they do not engage in a careful examination when they evaluate their life. They must be using heuristics, which are examples of both substitution and WYSIATI. Although their view of their life was influenced by a question about dating or by a coin on the copying machine, the participants in these studies did not forget that there is more to life than dating or feeling lucky. The concept of happiness is not suddenly changed by finding a dime, but System 1 readily substitutes a small part of it for the whole of it. Any aspect of life to which attention is directed will loom large in a global evaluation. This is the essence of the focusing illusion, which can be described in a single sentence:

Nothing in life is as important as you think it is when you are thinking about it.

The origin of this idea was a family debate about moving from California to Princeton, in which my wife claimed that people are happier in California than on the East Coast. I argued that climate is demonstrably not an important determinant of well-being—the Scandinavian countries are probably the happiest in the world. I observed that permanent life circumstances have little effect on well-being and tried in vain to convince my wife that her intuitions about the happiness of Californians were an error of affective forecasting.

A short time later, with this debate still on my mind, I participated in a workshop about the social science of global warming. A colleague made an argument that was based on his view of the well-being of the population of planet Earth in the next century. I argued that it was preposterous to forecast what it would be like to live on a warmer planet when we did not even know what it is like to live in California. Soon after that exchange, my colleague David Schkade and I were granted research funds to study two questions: Are people who live in California happier than others? and What are the popular beliefs about the relative happiness of Californians?

We recruited large samples of students at major state universities in California, Ohio, and Michigan. From some of them we obtained a detailed report of their satisfaction with various aspects of their lives. From others we obtained a prediction of how someone “with your interests and values” who lived elsewhere would complete the same questionnaire.

As we analyzed the data, it became obvious that I had won the family argument. As expected, the students in the two regions differed greatly in their attitude to their climate: the Californians enjoyed their climate and the Midwesterners despised theirs. But climate was not an important determinant of well-being. Indeed, there was no difference whatsoever between the life satisfaction of students in California and in the Midwest. We also found that my wife was not alone in her belief that Californians enjoy greater well-being than others. The students in both regions shared the same mistaken view, and we were able to trace their error to an exaggerated belief in the importance of climate. We described the error as a focusing illusion.

The essence of the focusing illusion is WYSIATI, giving too much weight to the climate, too little to all the other determinants of well-being. To appreciate how strong this illusion is, take a few seconds to consider the question:

How much pleasure do you get from your car?

An answer came to your mind immediately; you know how much you like and enjoy your car. Now examine a different question: “When do you get pleasure from your car?” The answer to this question may surprise you, but it is straightforward: you get pleasure (or displeasure) from your car when you think about your car, which is probably not very often. Under normal circumstances, you do not spend much time thinking about your car when you are driving it. You think of other things as you drive, and your mood is determined by whatever you think about. Here again, when you tried to rate how much you enjoyed your car, you actually answered a much narrower question: “How much pleasure do you get from your car when you think about it?” The substitution caused you to ignore the fact that you rarely think about your car, a form of duration neglect. The upshot is a focusing illusion. If you like your car, you are likely to exaggerate the pleasure you derive from it, which will mislead you when you think of the virtues of your current vehicle as well as when you contemplate buying a new one.

A similar bias distorts judgments of the happiness of Californians. When asked about the happiness of Californians, you probably conjure an image of someone attending to a distinctive aspect of the California experience, such as hiking in the summer or admiring the mild winter weather. The focusing illusion arises because Californians actually spend little time attending to these aspects of their life. Moreover, long-term Californians are unlikely to be reminded of the climate when asked for a global evaluation of their life. If you have been there all your life and do not travel much, living in California is like having ten toes: nice, but not something one thinks much about. Thoughts of any aspect of life are more likely to be salient if a contrasting alternative is highly available.

People who recently moved to California will respond differently. Consider an enterprising soul who moved from Ohio to seek happiness in a better climate. For a few years following the move, a question about his satisfaction with life will probably remind him of the move and also evoke thoughts of the contrasting climates in the two states. The comparison will surely favor California, and the attention to that aspect of life may distort its true weight in experience. However, the focusing illusion can also bring comfort. Whether or not the individual is actually happier after the move, he will report himself happier, because thoughts of the climate will make him believe that he is. The focusing illusion can cause people to be wrong about their present state of well-being as well as about the happiness of others, and about their own happiness in the future.

What proportion of the day do paraplegics spend in a bad mood?

This question almost certainly made you think of a paraplegic who is currently thinking about some aspect of his condition. Your guess about a paraplegic’s mood is therefore likely to be accurate in the early days after a crippling accident; for some time after the event, accident victims think of little else. But over time, with few exceptions, attention is withdrawn from a new situation as it becomes more familiar. The main exceptions are chronic pain, constant exposure to loud noise, and severe depression. Pain and noise are biologically set to be signals that attract attention, and depression involves a self-reinforcing cycle of miserable thoughts. There is therefore no adaptation to these conditions. Paraplegia, however, is not one of the exceptions: detailed observations show that paraplegics are in a fairly good mood more than half of the time as early as one month following their accident—though their mood is certainly somber when they think about their situation. Most of the time, however, paraplegics work, read, enjoy jokes and friends, and get angry when they read about politics in the newspaper. When they are involved in any of these activities, they are not much different from anyone else, and we can expect the experienced well-being of paraplegics to be near normal much of the time. Adaptation to a new situation, whether good or bad, consists in large part of thinking less and less about it. In that sense, most long-term circumstances of life, including paraplegia and marriage, are part-time states that one inhabits only when one attends to them.

One of the privileges of teaching at Princeton is the opportunity to guide bright undergraduates through a research thesis. And one of my favorite experiences in this vein was a project in which Beruria Cohn collected and analyzed data from a survey firm that asked respondents to estimate the proportion of time that paraplegics spend in a bad mood. She split herrespondents into two groups: some were told that the crippling accident had occurred a month earlier, some a year earlier. In addition, each respondent indicated whether he or she knew a paraplegic personally. The two groups agreed closely in their judgment about the recent paraplegics: those who knew a paraplegic estimated 75% bad mood; those who had to imagine a paraplegic said 70%. In contrast, the two groups differed sharply in their estimates of the mood of paraplegics a year after the accidents: those who knew a paraplegic offered 41% as their estimate of the time in that bad mood. The estimates of those who were not personally acquainted with a paraplegic averaged 68%. Evidently, those who knew a paraplegic had observed the gradual withdrawal of attention from the condition, but others did not forecast that this adaptation would occur. Judgments about the mood of lottery winners one month and one year after the event showed exactly the same pattern.

We can expect the life satisfaction of paraplegics and those afflicted by other chronic and burdensome conditions to be low relative to their experienced well-being, because the request to evaluate their lives will inevitably remind them of the life of others and of the life they used to lead. Consistent with this idea, recent studies of colostomy patients have produced dramatic inconsistencies between the patients’ experienced well-being and their evaluations of their lives. Experience sampling shows no difference in experienced happiness between these patients and a healthy population. Yet colostomy patients would be willing to trade away years of their life for a shorter life without the colostomy. Furthermore, patients whose colostomy has been reversed remember their time in this condition as awful, and they would give up even more of their remaining life not to have to return to it. Here it appears that the remembering self is subject to a massive focusing illusion about the life that the experiencing self endures quite comfortably.

Daniel Gilbert and Timothy Wilson introduced the word miswanting to describe bad choices that arise from errors of affective forecasting. This word deserves to be in everyday language. The focusing illusion (which Gilbert and Wilson call focalism) is a rich source of miswanting. In particular, it makes us prone to exaggerate the effect of significant purchases or changed circumstances on our future well-being.

Compare two commitments that will change some aspects of your life: buying a comfortable new car and joining a group that meets weekly, perhaps a poker or book club. Both experiences will be novel and exciting at the start. The crucial difference is that you will eventually pay little attention to the car as you drive it, but you will always attend to the social interaction to which you committed yourself. By WYSIATI, you are likely to exaggerate the long-term benefits of the car, but you are not likely to make the same mistake for a social gathering or for inherently attention-demanding activities such as playing tennis or learning to play the cello. The focusing illusion creates a bias in favor of goods and experiences that are initially exciting, even if they will eventually lose their appeal. Time is neglected, causing experiences that will retain their attention value in the long term to be appreciated less than they deserve to be.