The Introduction begins with personal stories from each author, and then explains the key book thesis, that humans are prone to self-deception about their motives. Key types of evidence are outlined, as is the trajectory of the book. Finally, readers are reminded that one can think ill of common human motives while still adoring humans overall.
Part I: Why we hide our motives
1. Animal Behavior
The Animal Behavior chapter surveys two examples of "hidden motive"-type behaviors in non-human animal species: social grooming among primates and competitive altruism in the Arabian babbler bird. At first blush, social grooming appears to serve a hygienic function, but on more careful inspection it turns out to be a political behavior. Similarly, individual babblers appear to act "for the good of the group," when in reality they're selfishly jockeying for prestige. These behaviors serve as analogues for the human behaviors we explore later in the book.
The Competition chapter argues that major facets of human physiology and behavior were sculpted by intra-group competition among our ancestors, in addition to their physical and ecological environment. We examine three important competitive games: sex, social status, and politics. In the sexual game, we compete for mates; in the status game, we compete for friends; and in the political game, we compete for power by forming coalitions and acting in concert with our allies. All three games involve sending and receiving signals of our qualities as a potential partner.
The Norms chapter introduces a suite of behaviors unique to the human species: the ability to make rules and to collectively enforce them within a group. Norms are important because they help suppress individual selfishness and promote collective welfare, enabling our species to partially escape the trap of the competitive games discussed in the previous chapter. The chapter begins by surveying the lifestyle of our hunter-gatherer ancestors, who lived in nomadic, egalitarian groups of 20-50 members. The egalitarian nature of this lifestyle was enabled in large part by weapons, which enabled a coalition of weaker group members to enforce norms on even the strongest members. The threat of gossip and the responsibility of maintaining one's reputation also helped with norm enforcement. The chapter also discusses a handful of subtle but important norms, including those against bragging, currying favor, sub-group politics, and (broadly) selfish motives.
The Cheating chapter describes how, in the face of norms, humans typically have incentives to cheat, at least when they think they can get away with it. The most interesting transgressions, however, aren't the blatant ones that have to be carefully covered up, but rather those that take place in broad daylight. When weak norms require common knowledge to prosecute violations, we can often get away with violating them by wearing the thinnest of fig leaves. As others are lazy and would rather not bother to enforce our norm violations, minor sins make it not seem worth the bother, discreet communication makes it harder to show what we said, and ready-made excuses make it harder for others to show our motives.
The Self-Deception chapter gets to the heart of the elephant, discussing why and how our brains conspire to distort reality and hide information. The Old School of self-deception, pioneered by Sigmund and Anna Freud, argued that we deceive ourselves as a defense mechanism. The New School of self-deception, a more evolutionary approach pioneered by Robert Trivers and Robert Kurzban, argues instead that we deceive ourselves in order to manipulate other people. In other words, we hide uncomfortable truths from ourselves (and occasionally substitute pretty fictions in their place) to more effectively mislead others about our own knowledge and intentions. Our brains are capable of these epistemic contortions because they are modular: composed of different pieces which aren't always consistent with each other. Perhaps the most subtle form of self-deception is self-discretion, wherein sensitive information is whispered rather than shouted by the different modules of the brain.
6. Counterfeit Reasons
The Counterfeit Reasons chapter looks at one particular form of self-deception: strategic ignorance about our motives. Experiments involving split-brain patients demonstrate that the human brain can fabricate bogus explanations out of whole cloth and deliver them as if they were the known truth. This tendency to "confabulate" or "rationalize" extends to healthy, whole-brain patients as well, and makes it difficult for us to know the truth about our own motives. According to this view of the mind, the ego (or self) acts less like a central executive making decisions, and more like a press secretary or public relations firm tasked with justifying those decisions to the public in the most plausible, prosocial way. And just as real-life press secretaries are often left in the dark to make their lives easier, our egos remain ignorant of many inner workings of our minds.
Part II: Hidden motives in everyday life
7. Body Language
The Body Language chapter poses a simple question: why are we often unaware of the messages sent by our bodies? A quick primer on body language (i.e., nonverbal communication) begins with the concept of an honest signal, one that (because of its cost) is difficult to fake - and much of our body language is backed by such honest signals. The chapter then explores the uses of body language in the domains of sex, politics, and social status. In all these domains, body language enables discreet coordination of potentially sensitive behaviors. This helps to explain why we are usually not consciously aware of the messages that our body language sends.
The Laughter chapter examines one of the strangest human behaviors: our propensity (and desire!) to erupt in fits of gasping and grunting. Despite millennia of failed efforts to decipher the meaning of laughter, 20th century biologists finally cracked the code. Laughter, both in humans and in our closest primate cousins, is a "play signal", a message that says, "Despite what seems like a threat, everything is great; we're just playing." We therefore laugh during play that hints at physical danger (tickling, wrestling, etc.), but also during play that hints at social danger. This includes mild norm violations, mock aggression, and real aggression directed at people we don't care about. Our natural ignorance about the meaning of laughter lets us avoid having to directly acknowledge what we're up to. Via laughter, we can say "I was just joshing" and "Can't you take a joke?"
The Conversation chapter investigates why we share information so freely with each other, given the costs of acquiring it and benefits of monopolizing it. A simple theory is that we're hoping for reciprocal exchange with our conversation partners: Alice tells Bob some juicy gossip today, and Bob returns the favor tomorrow. But this explanation fails to explain that 1) we don't keep track of conversational debts, 2) we are more eager to talk than to listen, 3) we prefer a continuous drift of "relevant" conversation topics, and 4) we often talk about unimportant trivia. A more compelling explanation is that we share information as an advertisement of our generic ability to know and learn things - an ability that makes us attractive as a potential friend, ally, lover, or leader. This chapter also discusses corollaries of this theory that help explain the news media and academic research.
The Consumption chapter examines a variety of hidden motives underlying consumer behavior. In 1899, Thorstein Veblen described a special type of signaling he called "conspicuous consumption," whereby consumers use luxury goods and services as a way to advertise their wealth. The underlying dynamic, however, is far broader. Consumer purchases help people show off many different qualities in addition to wealth, including conscientiousness and adventurousness. In fact, the enormous variety of products available to modern consumers is a testament to their use as signals. Advertising to wide audiences can create predictable and widespread associations between products and services and elements of individual identity. This can persuade buyers who wish to be associated with such identity elements.
The Art chapter looks at our motives for creating and appreciating art, i.e., things "made special," including pictures, sculpture, music, fiction, fashion, and more. For an analogy, consider bowerbirds, whose males build elaborate decorated structures solely to attract females. Male birds are selected for an ability to make bowers, and the raw energy to devote weeks to this task, while female birds are selected for an ability to discern impressive bowers. The fact that one can show energy by wasting effort is known as the "handicap principle." Two big clues to human motives on art are 1) our preference for impractical art, and 2) our caring greatly about "extrinsic" features of art, such as originality, techniques used, expense of materials, and how many artists contributed.
The Charity chapter looks at our motives for charity. Recently, Effective Altruism advocates have have tried to use hard data to choose the most effective projects, i.e., ones that most help those most in need. But only a small fraction of charity goes to those most in need, few donors think much about charity effectiveness, and we prefer more variety in our charity than is helpful to recipients. Donors do enjoy a "warm glow" from giving. But the question is: why? Some key clues: we prefer to help specific identifiable people near us, and we give more when we are watched, when thinking about mating, and when peers ask. A plausible explanation is that we seek to be seen by others as charitable, to signal our wealth, prosocial orientation, and empathy. This also helps explain many otherwise puzzling missing forms of charity.
The Education chapter asks: why do students go to school? Our usual public answer is "to learn the material." But that explanation leaves many puzzles, such as why few students learn for free via skipping the credentials, why students love canceled classes, and why employers pay more for irrelevant majors, and pay much more for the last year of high school and college. Students remember little of what they are taught, and most of that isn't useful. Plausibly, students go to school to show off their work potential to future employers, including their intelligence, conscientiousness, and conformity. School also plausibly functions to babysit students, to help students network and date, as a way for governments to indoctrinate citizens, and to domesticate and habituate students into modern workplace habits.
The Medicine chapter asks: why do use medicine? Our usual answer is: to get healthy. But it may also be conspicuous caring, like kissing a child's boo-boo. Our sick or injured forager ancestors needed allies to show political support, and historically people have wanted expensive medicine even when it made them worse. Today regions that consume more medicine aren't healthier on average, and the RAND health insurance experiment, using random assignment, found that people who consumed more medicine because it was free to them were not healthier. Conspicuous caring explains why we prefer visible sacrifice and effort, focus on dramatic health crises, spend more on medicine when our neighbors spend more, and care more about public than private signals of medical quality.
The Religion chapter asks: why are we religious? For religion we wear funny costumes, do complex rituals, mutilate our bodies, and generally waste vast resources. Many explain strange religious behavior as arising from strange religious beliefs. But beliefs aren't central to most religions, and we must explain why religious people have consistently better outcomes in health, work, marriage, and happiness. Most scholars say that religion is more about communities bonding together via common practices. One can show membership and loyalty to a group by sacrificing for it, joining in rituals of synchrony that create a sense of unity, and by showing visible badges. One can show allegiance to group norms by enforcing them, hearing sermons that affirm them, and believing in supernatural gods who punish violators. Even celibacy and martyrdom are plausibly overly extreme variations on functional religious behaviors.
The Politics chapter asks why we participate in democracy, not just by voting, but also by following political news, and discussing political topics. Our usual answer is that we are Do-Rights, helping our nation make better choices. But this Do-Right theory has trouble explaining why are so uninformed, care little about vote decisiveness, and have such such strong political emotions. Another answer is that we are Apparatchiks, showing loyalty to our many groups. We prefer to date, marry, talk with, and work with people who share our political affiliations. This answer better explains why we 1) vote more with group interest than self-interest, 2) care more about taking positions that influencing outcomes, 3) go out of our way to sacrifice, 4) let ourselves believe implausible claims, 5) distain compromise, and 6) align into a one dimensional political spectrum.
With humility, the Conclusion chapter sketches out some implications of the book's main thesis. Knowing about the elephant in the brain can help readers to better understand common social situations and their own mix of motives, and to show off personal honesty and courage. Readers might also reform themselves via a pragmatic idealism, choosing either to move their actions closer to their ideals or their ideals closer to their actions. Those who design institutional reforms can seek institutions that both appear to give people what they appear to want, while actually giving them what they really want. While such reforms are harder to design, they have a better chance of being actually adopted. Finally, readers are cautioned against becoming overly discouraged by this seemingly-cynical portrait. Humans get along with each other spectacularly well; our motives matter less than what we manage to achieve by them.