In fiction and in real-life law enforcement, the solving of a mystery involves something called “proof.” Science works a little differently. In most cases there’s no way to provide absolute proof that a solution to a scientific mystery is correct; often the best you can do is to demonstrate that alternative solutions fail to account for crucial aspects of the evidence. Sherlock Holmes, who prided himself on his scientific methods, was fond of saying, “When you have excluded the impossible, whatever remains, however improbable, must be the truth.”4 A real scientist would say something much less quotable—something like, “When you have excluded the highly improbable, whatever remains is, for the time being, in the realm of viable possibilities.”
Mysteries are my favorite leisure reading, but I usually choose something more up-to-date than Sherlock Holmes—for example, Sue Grafton’s alphabetical series, starting with “A” Is for Alibi. These mystery novels feature a detective named Kinsey Millhone, details of whose life have been revealed gradually over the course of the series. Learning about Kinsey is part of the fun of reading these books.
Like me, Kinsey doesn’t kowtow to authority, cuts her own hair, and is curious to a fault. She speaks in the first person and her books usually contain a passage like this in the first page or two:
My name is Kinsey Millhone. I’m a private investigator, licensed by the state of California…. I’m thirty-two years old, twice married, no kids, currently unattached and likely to remain so given my disposition.5
You might call me a private investigator too, since I investigate things on my own. In other respects, though, Kinsey and I are a continent apart. I live in New Jersey. I’m sixty-seven years old, still married to my first and only husband. Two nice kids, four lovely grandchildren. Currently attached to a number of people and likely to remain so in spite of my disposition.
But the most important difference between me and Kinsey is that she is strong and healthy and I am not. I have been ill for almost thirty years with a disorder that has been diagnosed as a mixture of systemic sclerosis and lupus, two autoimmune diseases that can each affect a variety of organs. Over the years, my immune system has launched attacks on many parts of my body. Now it has taken aim at my heart and lungs. About half of patients with systemic sclerosis eventually develop a debilitating malfunction of the heart and lungs called pulmonary hypertension. I was diagnosed with this malfunction in 2002.
To keep fit, Kinsey goes for three-mile runs; I get out of breath just walking at a normal speed. Kinsey is able to jump into her car and travel to distant places in search of clues; I can’t do that. I’m not entirely confined to my home—I do get out occasionally—but my physical stamina is so limited that I seldom venture farther than the local library or office supply store. When I go to the hospital for tests, my husband pushes me around in a wheelchair.
But there are fictional detectives more handicapped than I. In a mystery called The Daughter of Time—the title comes from an old proverb, “Truth is the daughter of time”—the detective does all his detecting while he’s flat on his back in the hospital. The novel, written by Josephine Tey and published in England in 1951, begins like this:
Grant lay on his high white cot and stared at the ceiling. Stared at it with loathing. He knew by heart every last minute crack on its nice clean surface.6
Alan Grant of Scotland Yard, hospitalized due to injuries he suffered while pursuing a malefactor, didn’t let his immobility stop him. With the aid of friends who brought him books and reproductions of old paintings, he found a mystery to solve: Who killed the Little Princes in the Tower?—a crime usually attributed to Richard III. Since the events in question occurred in the fifteenth century, Grant couldn’t have interviewed witnesses and suspects even if he had been sound in body. His detective work consisted, as one of his friends put it, of “academic investigating.”7
Academic investigating is a good description of what I do. There are many ways to collect evidence from far and wide while staying put. Unlike unlucky Alan Grant, I have access to the Internet and a wide circle of friends and colleagues with whom I correspond in e-mail. Some of my correspondents are privy to information that I wouldn’t have been able to obtain even if I were as healthy and mobile as Kinsey Millhone. But most of my evidence comes from published sources: scholarly books and articles in professional journals (see the endnotes and reference list at the back of this book). Other people do the legwork—the actual collecting of data—but once the outcome of their labors is published, it becomes grist for my mill. Even if I don’t agree with the researchers’ conclusions or approve of their methods—which, as you will see, is often the case—the published reports might contain something useful.
My first job is the same as Alan Grant’s: to convince you that there is a mystery in need of solving. Most of Grant’s contemporaries thought that the mystery had already been solved: “everyone knew” that it was Richard III who dunnit. Before Grant could set about identifying the real perpetrator, he had to show that the widely accepted solution was wrong. Almost three-quarters of the novel is devoted to convincing the reader that Richard did not kill the princes, the two young sons of his dead brother, Edward IV. With the aid of a young American researcher who has access to old documents stored in the British Museum, Grant establishes that Richard had no motive to have the boys put to death, that it would have been out of character for him to do so, and that in all probability they were still alive when Richard was killed at Bosworth—yelling, according to the account Shakespeare wrote a century later, “My kingdom for a horse!”
Most of my contemporaries think that the mystery of personality—of individuality, as I have called it in the subtitle of this book—has already been solved. It is commonly accepted that people turn out the way they do—different from one another, different from their brothers and sisters—because of “nature,” “nurture,” and/or some kind of interaction between the two.
“It is a capital mistake,” asserted Sherlock Holmes, “to theorize before one has data. Insensibly one begins to twist facts to suit theories.”8 In the real world, theories seldom spring to life in the total absence of data: one has to have something to begin with. But a theory may be formulated on the basis of inadequate, ambiguous, or misleading data. Then, insensibly one begins to collect more data in such a way that the new data tend to confirm the theory.
That sort of thing can go on for a remarkably long time: in psychology, for more than a hundred years. Then a new broom comes along and sweeps out the cobwebs by approaching the problem from a new angle. In psychology, there are two new brooms, both of which will be put to good use in this book: evolutionary psychology and behavioral genetics. Two new brooms that sweep in different directions—not opposite, but perpendicular to each other.
Evolutionary psychology is a science that regards the human mind as the product of Darwinian selection. At first glance it doesn’t look like a promising way to study human individuality. On the whole, evolutionary psychologists aren’t much interested in human differences: they are interested chiefly in what all humans have in common. Take, for example, the book How the Mind Works, by the evolutionary psychologist Steven Pinker.9 The “the” in the title is a giveaway. Pinker’s book is not about how my mind works or how yours does, but how everyone’s mind works. It’s about the standard equipment, not the optional stuff. Not the little blips and dings that make my mind work a little differently from yours.
Steven Pinker is actually an exception among evolutionary psychologists: in his latest book, The Blank Slate, he does talk about individual differences. But not until chapter 19. Here’s how The Blank Slate begins:
Everyone has a theory of human nature. Everyone has to anticipate the behavior of others, and that means we all need theories about what makes people tick.10
True enough, but the trouble is that having a theory of human nature doesn’t get us very far, because people don’t all behave alike. Knowing what makes one person tick—or a hundred people, for that matt
er—doesn’t help much in anticipating the behavior of the hundred and first.
Case in point: Matthew, the son of one of my e-mail friends, recently proposed to his girlfriend in front of a large group of people assembled at a formal dinner party. Fortunately, Alison said yes. But what if she had refused him, or said she’d have to think it over, or pointed to another man and said “I’d rather marry him”? How brave Matthew was, I thought, to take that risk in front of all those people.
Then it occurred to me that Matthew knew exactly what he was doing: he wouldn’t have proposed when and where he did (in fact, he probably wouldn’t have proposed at all) if he hadn’t been pretty sure of Alison’s response. His prediction of her behavior wasn’t based on his understanding of human nature—on his theory, let’s say, that women have a natural urge to get married. It was based on his understanding of Alison.
Admittedly, that interpretation of Matthew’s behavior is itself based on a theory of human nature. My belief that he wouldn’t have proposed in front of an audience if he hadn’t been pretty sure that Alison would say yes is based on my knowledge that humans do not, as a rule, enjoy being humiliated in public. So it is possible to predict human behavior to some extent. But that isn’t good enough. We need to be able to predict the behavior of specific others, and to do that we need to know what makes them tick. Not many people fly airplanes into office buildings, but some do.
People differ in behavior, and some of these individual differences persist over time. Some people are chronically more law-abiding, or less trusting, or friendlier, or more apt to get upset than others. Psychologists attribute these differences among individuals, and the consistencies within individuals, to differences in personality.
In a classic study, the social psychologists David Napolitan and George Goethals asked their subjects—undergraduates at Williams College—to have a brief face-to-face discussion with a woman posing as a graduate student in clinical psychology. The “graduate student” was actually a trained confederate of the researchers—trained to act in either a friendly or unfriendly manner with the subjects. With half the subjects she was warm and supportive; with the others she was aloof and critical.
After the discussion, the subjects were asked to fill out a questionnaire that included items about the personality of the graduate student. They were specifically instructed to evaluate her true personality, not just her behavior. But since the subjects had met the woman only once, they had nothing to go on other than her behavior during the discussion. Naturally, the ones who had seen her unfriendly persona rated her as cold and rejecting, and the ones who had seen her friendly persona rated her as warm and accepting.
The surprise came when the procedure was changed a little and new subjects were informed in advance that the graduate student was required, for the purposes of the study, to behave in a friendly or unfriendly manner. The additional information made no difference at all! Even when a student knew, while he was talking to the woman, that she had been instructed to behave in an aloof and critical way, he nonetheless rated her “true” personality as cold and unfriendly. He disregarded the fact that the situation demanded a certain kind of behavior from the grad student and attributed her behavior to an enduring characteristic—to her chronic predisposition to behave, and presumably to feel, in an unkind and unfriendly way.11
Many variations on Napolitan and Goethals’ experiment have been carried out, with similar results. The subjects always lean too far in attributing people’s behavior to their enduring characteristics; they invariably underestimate the power of the situation to compel a person to behave in a particular way. Only in regard to their own behavior are they likely to give adequate weight to the exigencies of the situation.
Social psychologists call it the “fundamental attribution error”—a grandiose name for something most people have never heard of, but “fundamental” is only a slight exaggeration. Though the magnitude of the error may vary somewhat across cultures, it is a human universal.12
“Everyone has to anticipate the behavior of others,” as Pinker pointed out. How do we do that when people vary so much in behavior? The answer, as shown by the fundamental attribution error, is that we take into account not just human nature in general but also the nature of particular humans. We are predisposed to see other people as having enduring characteristics that cause them to behave in predictable ways, and to interpret samples of behavior—even hopelessly inadequate samples—as clues to their characteristics. Our theory of human nature leads us to expect that people will be consistent—that if we meet the graduate student in the supermarket, she will be as nice or as nasty as she was in the laboratory.
The predisposition to attribute someone’s behavior to something within them that’s relatively stable and enduring—something that nowadays is called personality and that used to be called character—actually causes us to make errors in prediction: we expect people to be more consistent than they really are. It’s a reasonable error to make, however, because (in the absence of other information) the best predictor of how an individual will behave in the future is how he or she behaved in the past.13
At least to some extent, people are consistent. Some are habitually friendly; others are persistently hostile. In a classroom full of children (a classroom is a situation designed to produce uniformity of behavior), some children keep bothering their neighbors or talking out of turn, while others turn red and stammer if the teacher calls on them. They behave this way year after year, despite the turnover in teachers and classmates.
Evolutionary psychologists generally don’t say much about such differences, but they can’t do business without them. Individuality is incorporated into their theories, often without being explicitly acknowledged. Take mate selection, a major topic in this field. If you ask people what’s important to them in choosing a mate, both men and women list qualities like kindness, dependability, sincerity, and intelligence.14 If these are qualities that cause people to prefer some potential mates to others, then potential mates presumably differ in these ways. Some are judged to be kinder, more dependable, and more intelligent than others.
Of course, there are also differences in physical appearance; we find some individuals more attractive than others. But physical appearance has another, equally important function in mate selection: it’s the way we recognize individuals, the way we tell them apart. Though hearing and the sense of smell may also play a role, humans rely primarily on vision to identify individuals. If the selection of a long-term mate means learning about the qualities of specific individuals, then we have to be able to tell potential candidates apart and remember which one has which qualities. Choosing a mate is not just a matter of choosing someone of the right sex, the right shape, and the right age: it’s a matter of choosing a particular individual.
The ability to recognize and remember specific individuals also plays a crucial role in another aspect of human nature much discussed by evolutionary psychologists: altruism, which means helping someone else at a cost to oneself. At first glance, altruism seems at odds with a Darwinian viewpoint. Rescuing someone from a burning building entails a risk to the rescuer; yet, people do it. Since dying to save someone else’s life is hard to justify from a “survival of the fittest” point of view—death being the ultimate in unfitness—evolutionary theorists needed a way to explain it. In 1964, William Hamilton pointed out that altruism makes sense in terms of fitness (he called it “inclusive fitness”) if the one you are helping shares your genes. He even gave a formula for deciding, on the basis of how many genes you share with the other person—50 percent with a parent or child or sibling, 25 percent with a half-sibling or grandchild—whether you should bother.15
Hamilton’s theory, called kin selection or kin altruism, predicts that human and nonhuman animals should provide for their own offspring in preference to providing for the offspring of others. But in order to do this, the animal must have some way of identifying its own offspring. Evolution has come up with
a variety of solutions to this problem. A female sheep, for instance, has alternative ways of recognizing her offspring. Close up, the ewe relies on vision and her sense of smell to distinguish her own lamb from the others in the flock. When the lamb is too far away for scent or sight to be useful, she relies upon hearing. A ewe can recognize the sound of her own lamb’s voice.16
Consistent with the predictions of kin selection theory, animals of most species are nicer to their relatives than to nonrelatives. But humans also help others who are not related to them. That is the puzzle that led evolutionary psychologist Robert Trivers, in 1971, to propose the theory of reciprocal altruism.17 The idea is that helping others can increase your fitness because the others may be disposed to return the favor if you are ever in need. An example in nonhuman animals—in vampire bats, believe it or not—soon turned up. Drinking blood, as every moviegoer knows, is a precarious way to make a living; bats sometimes return home from a hard night’s work with an empty stomach. But vampire bats are a social species: they live in groups. And they help each other out. An unsuccessful hunter is usually able to get a handout, so to speak, of regurgitated blood from one of its more successful den mates. The successful hunter has gotten more than enough to meet its requirements, so it shares with the needy. Another night it might be the one in need, and then the recipient of its gift is expected to return the favor.18 Evolutionary psychologists, and economists in the field of game theory, call it “tit for tat.”
The thing about tit for tat is that it works only if the participants in the game are able to recognize and remember each other.19 Evidently vampire bats can do this, because they know which of their comrades owes them a favor and that’s the one they go to for a handout. Social animals that rely on reciprocal altruism to get them through hard times need to be able to tell one another apart. They need to know which members of their group are beholden to them and which can be relied upon to reciprocate. So they must be able to connect particular past experiences with particular individuals. They need a memory with a separate cache for each individual, because knowing that you’re talking to George and not to Donald is useless if you can’t remember whether it’s George or Donald who owes you a favor.
No Two Alike Page 2
