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

I think this book is mistitled. For years, I assumed that it was some kind of self-help book about when to trust your gut and when to trust your head, and thus I put off reading it. Butis nothing of the sort. As I finally discovered when the book was gifted to me (the ecstatic blurbs in the front pages were the first clue), this book is the summary of Daniel Kahneman’s study of cognitive errors. The book should probably be called:Granted, my initial impression had a grain of truth. Kahneman’s main focus is on what we sometimes call our gut. This is the “fast thinking” of the title, otherwise known as our intuition. Unlike many books on the market, which describe the wonders of human intuition and judgment, Kahneman’s primary focus was on how our intuition can systematically fail to draw correct conclusions. So you might say that this is a book about all of the reasons you should distrust your gut.Every researcher of the mind seems to divide it up into different hypothetical entities. For Freud it was the conscious and unconscious, while for Kahneman there are simply System 1 and System 2. The former is responsible for fast thinking—intuition, gut feelings—and the second is responsible for slow thinking—deliberative thought, using your head. System 2, while admirably thorough and logical, is also effortful and sluggish. Trying any unfamiliar mental task (such as mental arithmetic) can convince you of this. Thus, we must rely on our fast-acting System 1 for most of any given day.System 1 generates answers to questions without any experience of conscious deliberation. Most often these answers are reasonable, such as when answering the question “What you like a hamburger?” (Answer: yes). But, as Kahneman demonstrates, there are many situations in which the answer that springs suddenly to mind is demonstrably false. This would not be a problem if our conscious System 2 detected these falsehoods. Yet our default position is to simply go with our intuition unless we have a strong reason to believe our intuition is misleading. Unfortunately, the brain has no warning system to tell you that your gut feeling is apt to be unreliable. You can call these sorts of situations “cognitive illusions.”A common theme in these cognitive illusions is a failure of our intuition to deal with statistical information. We are good at thinking in terms of causes and comparisons, but situations involving chance throw us off. As an example, imagine a man who is shy, quiet, and orderly. Is he more likely to be a librarian or a farmer? Now consider the answer that springs to mind (librarian, I assume): how was it generated? Your mind compared the description to the stereotype of a librarian, and made the judgment. But this judgment did not take into account the fact that there are many times more farmers than male librarians.Another example of this failure of intuition is the mind’s tendency to generate causal stories to explain random statistical noise. A famous example of this is the “hot hand” in basketball: interpreting a streak of successful shots as due to the player being especially focused, rather than simply as a result a luck. (Although subsequent research has shown that there was something to the idea, after all. So maybe we should not lament too much about our intuitions!) Another well-known example is the tendency for traders to attribute their success or failure in the stock market to skill, while Kahneman demonstrated that the rankings of a group of traders from year to year had no correlation at all. The basic point is that we are generally hesitant to attribute something to chance, and instead invent causal stories that “explain” the variation.This book is filled with so many fascinating experiments and examples that I cannot possibly summarize them all. Suffice to say that the results are convincing, not only because of the weight of evidence, but mainly because Kahneman is usually able to demonstrate the principle at work on the reader. Our intuitive reactions are remarkably similar, apparently, and I found that I normally reacted to his questions in the way that he predicted. If you are apt to believe that you are a rational person (as I am) it can be quite depressing.After establishing the groundwork, Kahneman sets his sights on the neighboring discipline of economics. Conventional economic theory presupposes rational actors who are able to weigh risks and to act in accordance with their desires. But, as Kahneman found, this does hold with actual people. Not only do real humans act irrationally, but real humans deviate from the expected predictions of the rational agent model. This means that we humans are (to borrow a phrase from another book in this vein) predictably irrational. Our folly is consistent.One major finding is that people are loss-averse. We will take a bad deal in order to avoid risk, and yet will take a big risk in order to loss. This behavior seems to be motivated by an intense fear of regret, and it is the cause of a certain amount of conservatism, not only in economics, but in life. If an action turns out badly, we tend to regret it more of it was an exceptional rather than a routine act (picking up a hitchhiker rather than driving to work, for example), and so people shy away from abnormal options that carry uncertainty.Yet, logically speaking, there is no reason to regret a special action more than a customary one, just as there is no reason to weigh losses so much more heavily than gains. Of course, there is good evolutionary logic for these tendencies. In a dangerous environment, losing a gamble could mean losing your life, so it is best to stay to the tried-and-true. But in an economic context, this strategy is not usually optimal.The last section of the book was the most interesting of all, at least from a philosophical perspective. Kahneman investigates how our memories systematically misrepresent our experiences, which can cause a huge divergence between experienced happiness and remembered joy. Basically, when it comes to memory, intensity matters more than duration, and the peaks and ends of experiences matter more than their averages. The same applies with pain: We may remember one experience as less painful than another just because the pain was mild when it ended. And yet, in terms of measured pain per minute, the first experience may actually have included more experiential suffering.As a result of this, our evaluations of life satisfaction can often have very little to do with our real, experiential well being. This presents us with something of a paradox, since we often do things, not for how much joy they will bring us in the moment, but for the nice memory they will create. Think about this: How much money would you spend on a vacation if you knew that every trace of the experience would be wiped out as soon as the vacation ended, including photos and even your memories? The answer for most people is not much, if anything at all. This is why so many people (myself included) frantically take photos on their vacations: the vacation is oriented toward a future remembering-self. But perhaps it is just as well that humans were made this way. If I made my decisions based on what was most pleasant to do in the moment, I doubt I would have made my way through Kant.This is just a short summary of the book, which certainly does not do justice to the richness of Kahneman’s many insights, examples, and arguments. What can I possibly add? Well, I think I should begin with my few criticisms. Now, it is always possible to criticize the details of psychological experiments—they are artificial, they mainly use college students, etc. But considering the logistical restraints of doing research, I thought that Kahneman’s experiments were all quite expertly done, with the relevant variables controlled and additional work performed to check for competing explanations. So I cannot fault this.What bothered me, rather, was that Kahneman was profuse in diagnosing cognitive errors, but somewhat reticent when it came to the practical ramifications of these conclusions, or to strategies to mitigate these errors. He does offer some consequences and suggestions, but these are few and far between. Of course, doing this is not his job, so perhaps it is unfair to expect anything of the kind from Kahneman. Still, if anyone is equipped to help us deal with our mental quagmires, he is the man.This is a slight criticism. A more serious shortcoming was that his model of the mind fails to account for a ubiquitous experience: boredom. According to Kahneman’s rough sketch, System 1 is pleased by familiarity, and System 2 is only activated (begrudgingly, and without much relish) for unfamiliar challenges. Yet there are times when familiarity can be crushing and when novel challenges can be wonderfully refreshing. The situation must be more subtle: I would guess that we are most happy with moderately challenging tasks that take place against a familiar background. In any case, I think that Kahneman overstated our intellectual laziness.Pop psychology—if this book can be put under that category—is a genre I dip into occasionally. Though there is a lot of divergence in emphasis and terminology, the consensus is arguably more striking. Most authors seem to agree that our conscious mind is rather impotent compared to all of the subconscious control exerted by our brains. Kahneman’s work in the realm of judgments closely parallels Johathan Haidt’s work in morals: that our conscious mind mostly just passively accepts verdicts handed up from our mental netherworld. Indeed, arguably this was Freud’s fundamental message, too. Yet it is so contrary to all of our conscious experiences (as, indeed, it must be) that it still manages to be slightly disturbing.Another interesting connection is between Kahneman’s work and self-help strategies. It struck me that these cognitive errors are quite directly related to Cognitive Behavioral Therapy, which largely consists of getting patients to spot their own mental distortions (most of which are due to our mind’s weakness with statistics) and correct them. And Kahneman’s work on experiential and remembered well being has obvious relevance to the mindfulness movement—strategies for switching our attention from our remembering to our experiencing “self.” As you can see from these connections, Kahneman’s research is awfully rich.Though perhaps not as amazing as the blurbs would have you believe, I cannot help but conclude that this is a thoroughly excellent book. Kahneman gathers many different strands of research together into a satisfying whole. Who would have thought that a book about all the ways that I am foolish would make me feel so wise?