Subliminal: how your unconscious mind rules your behavior - Leonard Mlodinow 2013
The Importance of Being Social
The Two-Tiered Brain
Strange is our situation here on earth. Each of us comes for a short visit, not knowing why, yet sometimes seeming to a divine purpose. From the standpoint of daily life, however, there is one thing we do know: that we are here for the sake of others. —ALBERT EINSTEIN
I CAME HOME FROM work late one evening, hungry and frustrated, and popped into my mother’s house, which was next door to mine. She was eating a frozen dinner and sipping from a mug of hot water. CNN blared on the TV in the background. She asked how my day had been. I said, “Oh, it was good.” She looked up from her black plastic food tray and, after a moment, said, “No, it wasn’t. What happened? Have some pot roast.” My mother was eighty-eight, hard of hearing, and half blind in her right eye—which was her good eye. But when it came to perceiving her son’s emotions, my mother’s X-ray vision was unimpaired.
As she read my mood with such fluency, I thought about the man who had been my coworker and partner in frustration that day—the physicist Stephen Hawking, who could hardly move a muscle, thanks to a forty-five-year struggle with motor neuron disease. By this stage in the progression of his illness, he could communicate only by painstakingly twitching the cheek muscle under his right eye. That twitch was detected by a sensor on his glasses and communicated to a computer in his wheelchair. In this manner, with the help of some special software, he managed to select letters and words from a screen, and eventually to type out what he wanted to express. On his “good” days, it was as if he were playing a video game where the prize was the ability to communicate a thought. On his “bad” days, it was as if he were blinking in Morse code but had to look up the dot and dash sequence between each letter. On the bad days—and this had been one of them—our work was frustrating for both of us. And yet, even when he could not form words to express his ideas about the wave function of the universe, I had little trouble detecting when his attention shifted from the cosmos to thoughts of calling it quits and moving on to a nice curry dinner. I always knew when he was content, tired, excited, or displeased, just from a glance at his eyes. His personal assistant had this same ability. When I asked her about it, she described a catalog of expressions she’d learned to recognize over the years. My favorite was “the steely-faced glint of glee” he displayed when composing a potent rejoinder to someone with whom he strongly disagreed. Language is handy, but we humans have social and emotional connections that transcend words, and are communicated—and understood—without conscious thought.
The experience of feeling connected to others seems to start very early in life. Studies on infants show that even six-month-olds make judgments about what they observe of social behavior.1 In one such study infants watched as a “climber,” which was nothing more than a disk of wood with large eyes glued onto its circular “face,” started at the bottom of a hill and repeatedly tried but failed to make its way to the top. After a while, a “helper,” a triangle with similar eyes glued on, would sometimes approach from farther downhill and help the climber with an upward push. On other attempts, a square “hinderer” would approach from uphill and shove the circular disk back down.
The experimenters wanted to know if the infants, unaffected and uninvolved bystanders, would cop an attitude toward the hinderer square. How does a six-month-old show its disapproval of a wooden face? The same way six-year-olds (or sixty-year-olds) express social displeasure: by refusing to play with it. That is, when the experimenters gave the infants a chance to reach out and touch the figures, the infants showed a definite reluctance to reach for the hinderer square, as compared to the helper triangle. Moreover, when the experiment was repeated with either a helper and a neutral bystander block or a hinderer and a neutral block, the infants preferred the friendly triangle to the neutral block, and the neutral block to the nasty square. Squirrels don’t set up foundations to cure rabies, and snakes don’t help strange snakes cross the road, but humans place a high value on kindness. Scientists have even found that parts of our brain linked to reward processing are engaged when we participate in acts of mutual cooperation, so being nice can be its own reward.2 Long before we can verbalize attraction or revulsion, we are attracted to the kind and repelled by the unkind.
One advantage of belonging to a cohesive society in which people help one another is that the group is often better equipped than an unconnected set of individuals to deal with threats from the outside. People intuitively realize that there is strength in numbers and take comfort in the company of others, especially in times of anxiety or need. Or, as Patrick Henry famously said, “United we stand, divided we fall.” (Ironically, Henry collapsed and fell into the arms of bystanders shortly after uttering the phrase.)
Consider a study performed in the 1950s. About thirty female students at the University of Minnesota, none of whom had previously met, were ushered into a room and asked not to speak to each other.3 In the room was a “gentleman of serious mien, horn-rimmed glasses, dressed in a white laboratory coat, stethoscope dribbling out of his pocket, behind him an array of formidable electrical junk.” Seeking to induce anxiety, he melodramatically introduced himself as “Dr. Gregor Zilstein of the Medical School’s Departments of Neurology and Psychiatry.” Actually, he was Stanley Schachter, a harmless professor of social psychology. Schachter told the students he had asked them there to serve as subjects in an experiment on the effects of electric shocks. He would be shocking them, he said, and studying their reactions. After going on for seven or eight minutes about the importance of the research, he concluded by saying,
“These shocks will hurt, they will be painful.… It is necessary that our shocks be intense.… [We will] hook you into apparatus such as this [motioning toward the scary equipment behind him], give you a series of shocks, and take various measures such as your pulse rate, blood pressure, and so on.”
Schachter then told the students that he needed them to leave the room for about ten minutes while he brought in still more equipment and set it all up. He noted that there were many rooms available, so they could wait either in a room by themselves or in one with other subjects. Later, Schachter repeated the scenario with a different group of about thirty students. But this time, he aimed to lull them into a state of relaxation. And so, instead of the scary part about intense shocks, he said,
“What we will ask each of you to do is very simple. We would like to give each of you a series of very mild electric shocks. I assure you that what you feel will not in any way be painful. It will resemble more a tickle or a tingle than anything unpleasant.”
He then gave these students the same choice about waiting alone or with others. In reality, that choice was the climax of the experiment; there would be no electric shocks for either group.
The point of the ruse was to see if, because of their anxiety, the group expecting a painful shock would be more likely to seek the company of others than the group not expecting one. The result: about 63 percent of the students who were made anxious about the shocks wanted to wait with others, while only 33 percent of those expecting tickly, tingly shocks expressed that preference. The students had instinctively created their own support groups. It’s a natural instinct. A quick look at a web directory of support groups in Los Angeles, for example, turned up groups focused on abusive behavior, acne, Adderall addiction, addiction, ADHD, adoption, agoraphobia, alcoholism, albinism, Alzheimer’s, Ambien users, amputees, anemia, anger management, anorexia, anxiety, arthritis, Asperger’s syndrome, asthma, Ativan addiction, and autism—and that’s just the A’s. Joining support groups is a reflection of the human need to associate with others, of our fundamental desire for support, approval, and friendship. We are, above all, a social species.
Social connection is such a basic feature of human experience that when we are deprived of it, we suffer. Many languages have expressions—such as “hurt feelings”—that compare the pain of social rejection to the pain of physical injury. Those may be more than just metaphors. Brain-imaging studies show that there are two components to physical pain: an unpleasant emotional feeling and a feeling of sensory distress. Those two components of pain are associated with different structures in the brain. Scientists have discovered that social pain is also associated with a brain structure called the anterior cingulate cortex—the same structure involved in the emotional component of physical pain.4
It’s fascinating that the pain of a stubbed toe and the sting of a snubbed advance share a space in your brain. The fact that they are roommates gave some scientists a seemingly wild idea: Could painkillers that reduce the brain’s response to physical brain also subdue social pain?5 To find out, researchers recruited twenty-five healthy subjects to take two tablets twice each day for three weeks. Half received extra-strength Tylenol (acetaminophen) tablets, the other half placebos. On the last day, the researchers invited the subjects, one by one, into the lab to play a computer-based virtual ball-tossing game. Each person was told they were playing with two other subjects located in another room, but in reality those roles were played by the computer, which interacted with the subjects in a carefully designed manner. In round 1, those reputedly human teammates played nicely with the subjects, but in round 2, after tossing the virtual ball to the subject a few times, the teammates started playing only with each other, rudely excluding the subject from the game, like soccer players who refuse to pass the ball to a peer. After the exercise, the subjects were asked to fill out a questionnaire designed to measure social distress. Compared to those who took the placebo, those who took the Tylenol reported a reduced level of hurt feelings.
There was also a twist. Remember Antonio Rangel’s experiment in which the subjects tasted wine while having their brains scanned in an fMRI machine? These researchers employed the same technique—they had the subjects play the virtual ball game while lying in an fMRI machine. So while they were being snubbed by their teammates, their brains were being scanned by the machine. It showed that the subjects who’d taken Tylenol had reduced activity in the brain areas associated with social exclusion. Tylenol, it seems, really does reduce the neural response to social rejection.
When the Bee Gees long ago sang “How Can You Mend a Broken Heart?” they probably didn’t foresee that the answer was to take two Tylenols. That Tylenol would help really does sound far-fetched, so the brain researchers also performed a clinical test to see if Tylenol had the same effect outside the lab, in the real world of social rejection. They asked five dozen volunteers to fill out a “hurt feelings” survey, a standard psychological tool, every day for three weeks. Again, half the volunteers took a dose of Tylenol twice a day, while the other half took a placebo. The result? The volunteers on Tylenol did indeed report significantly reduced social pain over that time period.
The connection between social pain and physical pain illustrates the links between our emotions and the physiological processes of the body. Social rejection doesn’t just cause emotional pain; it affects our physical being. In fact, social relationships are so important to humans that a lack of social connection constitutes a major risk factor for health, rivaling even the effects of cigarette smoking, high blood pressure, obesity, and lack of physical activity. In one study, researchers surveyed 4,775 adults in Alameda County, near San Francisco.6 The subjects completed a questionnaire asking about social ties such as marriage, contacts with extended family and friends, and group affiliation. Each individual’s answers were translated into a number on a “social network index,” with a high number meaning the person had many regular and close social contacts and a low number representing relative social isolation. The researchers then tracked the health of their subjects over the next nine years. Since the subjects had varying backgrounds, the scientists employed mathematical techniques to isolate the effects of social connectivity from risk factors such as smoking and the others I mentioned above, and also from factors like socioeconomic status and reported levels of life satisfaction. They found a striking result. Over the nine-year period, those who’d placed low on the index were twice as likely to die as individuals who were similar with regard to other factors but had placed high on the social network index. Apparently, hermits are bad bets for life insurance underwriters.
SOME SCIENTISTS BELIEVE that the need for social interaction was the driving force behind the evolution of superior human intelligence.7 After all, it is nice to have the mental capacity to realize that we live in a curved four-dimensional space-time manifold, but unless the lives of early humans depended on having a GPS unit to locate the nearest sushi restaurant, the capability to develop such knowledge was not important to the survival of our species and, hence, did not drive our cerebral evolution. On the other hand, social cooperation and the social intelligence it requires seem to have been crucial to our survival. Other primates also exhibit social intelligence, but not nearly to the extent that we do. They may be stronger and faster, but we have the superior ability to band together and coordinate complex activities. Do you need to be smart to be social? Could the need for innate skill at social interaction have been the reason we developed our “higher” intelligence—and could what we usually think of as the triumphs of our intelligence, such as science and literature, be just a by-product?
Eons ago, having a sushi dinner involved skills a bit more advanced than saying, “Pass the wasabi.” It required catching a fish. Before about fifty thousand years ago, humans did not do that; nor did they eat other animals that were available but difficult to catch. Then, rather abruptly (on the evolutionary scale of time), humans changed their behavior.8 According to evidence uncovered in Europe, within the span of just a few millennia people started fishing, catching birds, and hunting down dangerous but tasty and nutritious large animals. At about the same time, they also started building structures for shelter and creating symbolic art and complex burial sites. Suddenly they had both figured out how to gang up on woolly mammoths and begun to participate in the rituals and ceremonies that are the rudiments of what we now call culture. In a brief period of time, the archaeological record of human activity changed more than it had in the previous million years. The sudden manifestation of the modern capacity for culture, ideological complexity, and cooperative social structure—without any change in human anatomy to explain it—is evidence that an important mutation may have occurred within the human brain, a software upgrade, so to speak, that enabled social behavior and thereby bestowed on our species a survival advantage.
When we think of humans versus dogs and cats, or even monkeys, we usually assume that what distinguishes us is our IQ. But if human intelligence evolved for social purposes, then it is our social IQ that ought to be the principal quality that differentiates us from other animals. In particular, what seems special about humans is our desire and ability to understand what other people think and feel. Called “theory of mind,” or “ToM,” this ability gives humans a remarkable power to make sense of other people’s past behavior and to predict how their behavior will unfold given their present or future circumstances. Though there is a conscious, reasoned component to ToM, much of our “theorizing” about what others think and feel occurs subliminally, accomplished through the quick and automatic processes of our unconscious mind. For example, if you see a woman racing toward a bus that pulls away before she can get on it, you know without giving it any thought that she was frustrated and possibly ticked off about not reaching the bus in time, and when you see a woman moving her fork toward and away from a piece of chocolate cake, you assume she’s concerned about her weight. Our tendency to automatically infer mental states is so powerful that we apply it not only to other people but to animals and even, as the six-month-olds did in the wooden disk study I described above, to inanimate geometrical shapes.9
It is difficult to overestimate the importance to the human species of ToM. We take the operation of our societies for granted, but many of our activities in everyday life are possible only as a result of group efforts, of human cooperation on a large scale. Building a car, for example, requires the participation of thousands of people with diverse skills, in diverse lands, performing diverse tasks. Metals like iron must be extracted from the ground and processed; glass, rubber, and plastics must be created from numerous chemical precursors and molded; batteries, radiators, and countless other parts must be produced; electronic and mechanical systems must be designed; and it all must come together, coordinated from far and wide, in one factory so that the car can be assembled. Today, even the coffee and bagel you might consume while driving to work in the morning is the result of the activities of people all over the world—wheat farmers in one state, bakers most likely in another, dairy farmers yet elsewhere; coffee plantation workers in another country, and roasters hopefully closer to you; truckers and merchant marines to bring it all together; and all the people who make the roasters, tractors, trucks, ships, fertilizer, and whatever other devices and ingredients are involved. It is ToM that enables us to form the large and sophisticated social systems, from farming communities to large corporations, upon which our world is based.
Scientists are still debating whether nonhuman primates use ToM in their social activities, but if they do, it seems to be at only a very basic level.10 Humans are the only animal whose relationships and social organization make high demands on an individual’s ToM. Pure intelligence (and dexterity) aside, that’s why fish can’t build boats and monkeys don’t set up fruit stands. Pulling off such feats makes human beings unique among the animals. In our species, rudimentary ToM develops in the first year. By age four, nearly all human children have gained the ability to assess other people’s mental states.11 When ToM breaks down, as in autism, people can have difficulty functioning in society. In his book An Anthropologist on Mars, the clinical neurologist Oliver Sacks profiled Temple Grandin, a high-functioning autistic woman. She had told him about what it was like to go to the playground when she was a child, observing the other children’s responses to social signals she could not herself perceive. “Something was going on between the other kids,” he described her as thinking, “something swift, subtle, constantly changing—an exchange of meanings, a negotiation, a swiftness of understanding so remarkable that sometimes she wondered if they were all telepathic.”12
One measure of ToM is called intentionality.13 An organism that is capable of reflecting about its own state of mind, about its own beliefs and desires, as in I want a bite of my mother’s pot roast—is called “first-order intentional.” Most mammals fit in that category. But knowing about yourself is a far different skill from knowing about someone else. A second-order intentional organism is one that can form a belief about someone else’s state of mind, as in I believe my son wants a bite of my pot roast. Second-order intentionality is defined as the most rudimentary level of ToM, and all healthy humans have it, at least after their morning coffee. If you have third-order intentionality you can go a step further, reasoning about what a person thinks a second person thinks, as in I believe my mom thinks that my son wants a bite of her pot roast. And if you are capable of going a level beyond that, of thinking I believe my friend Sanford thinks that my daughter Olivia thinks that his son Johnny thinks she is cute or I believe my boss, Ruth, knows that our CFO, Richard, thinks that my colleague John doesn’t believe her budgets and revenue projections can be trusted, then you’re engaging in fourth-order intentionality, and so on. Fourth-order thinking makes for a pretty complicated sentence, but if you ponder these for a minute, you’ll probably realize you engage in it quite frequently, for it is typical of what is involved in human social relationships.
Fourth-order intentionality is required to create literature, for writers must make judgments based on their own experiences of fourth-order intentionality, such as I think that the cues in this scene will signal to the reader that Horace thinks that Mary intends to dump him. It is also necessary for politicians and business executives, who could easily be outmaneuvered without that skill. For example, I knew a newly hired executive at a computer games company—call her Alice—who used her highly developed ToM to get out of a touchy situation. Alice felt certain that an outside company that had a long-term contract for programming services with her new employer was guilty of certain financial improprieties. Alice had no proof, and the outside company had an airtight long-term contract that required a $500,000 payment for early termination. But: Alice knew that Bob (the CEO of the outside company) knew that Alice, being new on the job, was afraid to make a misstep. That’s third-order intentionality. Also: Alice knew that Bob knew that she knew that Bob was not afraid of a fight. That’s fourth-order thinking. Understanding this, Alice considered a ploy: What if she made a bluff that she had proof of the impropriety and used that to force Bob to let them out of the contract? How would Bob react? She used her ToM analysis to look at the situation from Bob’s point of view. Bob saw her as someone who was hesitant to take chances and who knew that he was a fighter. Would such a person make a grand claim she couldn’t back up? Bob must have thought not, for he agreed to let Alice’s employer out of the contract for a small fraction of the contractually obligated sum.
The evidence on nonhuman primates seems to show that they fall somewhere between first- and second-order thinking. A chimp may think to itself, I want a banana or even I believe George wants my banana, but it wouldn’t go as far as thinking, I believe George thinks that I want his banana. Humans, on the other hand, commonly engage in third- and fourth-order intentionality and are said to be capable of sixth-order. Tackling those higher-order ToM sentences taxes the mind in a way that, to me, feels analogous to the thinking required when doing research in theoretical physics, in which one must be able to reason about long chains of interrelated concepts.
If ToM both enables social connection and requires extraordinary brain power, that may explain why scientists have discovered a curious connection between brain size and social group size among mammals. To be precise, the size of a species’ neocortex—the most recently evolved part of the brain—as a percentage of that species’ whole brain seems to be related to the size of the social group in which members of that species hang out.14 Gorillas form groups of under ten, spider monkeys closer to twenty, and macaques more like forty—and these numbers accurately reflect the neocortex-to-whole-brain ratio of each of these species.
Suppose we use the mathematical relationship that describes the connection between group size and relative neocortex size in nonhuman primates to predict the size of human social networks. Does it work? Does the ratio of neocortex to overall brain size apply to calculating the size of human networks, too?
To answer that question, we first have to come up with a way of defining group size among humans. Group size in nonhuman primates is defined by the typical number of animals in what are called grooming cliques. These are social alliances like the cliques our kids form in school or those adults have been known to form at the PTA. In primates, clique members regularly clean each other, removing dirt, dead skin, insects, and other objects by stroking, scratching, and massaging. Individuals are particular about both whom they groom and whom they are groomed by, because these alliances act as coalitions to minimize harassment from others of their kind. Group size in humans is harder to define in any precise way because humans relate to one another in many different types of groups, with different sizes, different levels of mutual understanding, and different degrees of bonding. In addition, we have developed technologies designed specifically to aid large-scale social communication, and we have to be careful to exclude from group size measurements people such as e-mail contacts we hardly know. In the end, when scientists look at groups that seem to be the cognitive equivalent of nonhuman grooming cliques—the clans among Australian aboriginals, the hair-care networks of female bushmen, or the number of individuals to whom people send Christmas cards—the human group size comes out to about 150, just about what the neocortex size model predicts.15
Why should there be a connection between brain power and the number of members in a social network? Think about human social circles, circles consisting of friends and relatives and work associates. If these are to remain meaningful, they can’t get too big for your cognitive capacities, or you won’t be able to keep track of who is who, what they all want, how they relate to one another, who can be trusted, who can be counted on to help out with a favor, and so on.16
To explore just how connected we humans are, in the 1960s the psychologist Stanley Milgram selected about 300 people at random in Nebraska and Boston and asked each of them to start a chain letter.17 The volunteers were sent a packet of materials with a description of the study, including the name of a “target person”—a randomly chosen man in Sharon, Massachusetts, who worked as a stockbroker in Boston. They were instructed to forward the packet to the target person if they knew him or, if they didn’t, to send it to whichever of their acquaintances they deemed most likely to know him. The intention was that the acquaintance, upon receiving the packet, would also follow the instructions and send it along, until eventually someone would be found who did know the target person and would send it directly to him.
Many people along the way didn’t bother, and broke the chain. But out of the initial 300 or so individuals, 64 did generate chains that ultimately found the man in Sharon, Massachusetts. How many intermediaries did it take until someone knew someone who knew someone who knew someone … who knew the target? The median number was only about 5. The study led to the coining of the term “six degrees of separation,” based on the idea that six links of acquaintanceship are enough to connect any two people in the world. The same experiment, made much easier by the advent of e-mail, was repeated in 2003.18 This time the researchers started with 24,000 e-mail users in more than 100 countries, and 18 different target people spread far and wide. Of the 24,000 e-mail chains those subjects started, only about 400 reached their target. But the result was similar: the target was contacted in a median of five to seven steps.
We give out Nobel Prizes in scientific fields like physics and chemistry, but the human brain also deserves a gold medallion for its extraordinary ability to create and maintain social networks, such as corporations, government agencies, and basketball teams, in which people work smoothly together to accomplish a common goal with a minimum of miscommunication and conflict. Perhaps 150 is the natural group size for humans in the wild, unaided by formal organizational structures or communications technology, but given those innovations of civilization, we have blasted through the natural barrier of 150 to accomplish feats that only thousands of humans working together could possibly attain. Sure, the physics behind the Large Hadron Collider, a particle accelerator in Switzerland, is a monument to the human mind. But so are the scale and complexity of the organization that built it—one LHC experiment alone required more than 2,500 scientists, engineers, and technicians in 37 countries to work together, solving problems cooperatively in an ever-changing and complex environment. The ability to form organizations that can create such achievements is as impressive as the achievements themselves.
THOUGH HUMAN SOCIAL behavior is clearly more complex than social behavior in other species, there are also striking commonalities in certain fundamental aspects of the way all mammals connect with others of their species. One of the interesting aspects of most nonhuman mammals is that they are “small-brained.” By that, scientists mean the part of the brain that in humans is responsible for conscious thought is, in nonhuman mammals, relatively small compared to the part of the brain involved in unconscious processes.19 Of course, no one is quite sure exactly how conscious thought arises, but it seems to be centered mainly in the frontal lobe of the neocortex, in particular in a region called the prefrontal cortex. In other animals, these regions of the brain are either much smaller or nonexistent. In other words, animals react more and think less, if at all. So a human’s unconscious mind might raise an alarm at the sight of Uncle Matt stabbing his arm with a shish kebab skewer, only to have the conscious mind remind that human that Uncle Matt thinks it is funny to perform shocking magic tricks. Your pet rabbit’s reaction, in contrast, would probably not be mitigated by such conscious, rational considerations. The rabbit’s reaction would be automatic. It would follow its gut instincts and simply flee Uncle Matt and his skewer. But although a rabbit just can’t take a joke, the brain regions responsible for a rabbit’s unconscious processing are not that different from ours.
In fact, the organization and chemistry of the unconscious brain is shared across mammal species, and many automatic neural mechanisms in apes and monkeys and even lower mammals are similar to our own, and produce startlingly humanlike behavior.20 So although other animals can’t teach us much about ToM, they they can provide insights into some of the other automatic and unconscious aspects of our social tendencies. That’s why, while other people read books like Men Are from Mars, Women Are from Venus to learn about male and female social roles, I turn to sources like “Mother-Infant Bonding and the Evolution of Mammalian Social Relationships”—which, some say, serves to minimize the mammalian social relationships in my own life.
Consider this quote from that work:
Reproductive success in males is generally determined by competing with other males to mate with as many females as possible. Hence, males rarely form strong social bonds and male coalitions are typically hierarchical with an emphasis on aggressive rather than affiliative behavior.21
That sounds like something you’d observe hanging out at a sports bar, but scientists are discussing the behavior of nonhuman mammals. Perhaps the difference between human males and bulls, tomcats, and male sheep is not that nonhuman mammals don’t have sports bars but that, to nonhuman mammals, the whole world is a sports bar. Of females, those same researchers write:
The female reproductive strategy is one of investing in the production of a relatively few offspring … and success is determined by the quality of care and the ability to enable infant survival beyond the weaning age. Females therefore form strong social bonds with their infants and female-female relationships are also strongly affiliative.
That, too, sounds familiar. One has to be careful about reading too much into mammalian behavior “in general,” but this does seem to explain why it is mostly women who have slumber parties and form book clubs, and why, despite my promises to be affiliative rather than aggressive, they have never let me into either. The fact that on some level human and nonhuman mammals seem to behave similarly does not mean that a cow would enjoy a candlelight dinner, that a mother sheep wants nothing more than to see her babies grow up happy and well-adjusted, or that rodents aspire to retiring in Tuscany with their soul mates. What it does suggest is that although human social behavior is far more complex than that of other animals, the evolutionary roots of our behaviors can be found in those animals, and we can learn something about ourselves by studying them.
Just how programmed is the social behavior of nonhuman mammals? Take sheep, for example.22 A female sheep—a ewe—is by disposition rather nasty to baby sheep (or, as the meat industry likes us to call them, lambs). If a lamb approaches, wishing to suckle, the ewe will scream at it with a high-pitched bleat, and maybe throw in a head butt or two. However, the birthing process transforms the mother. It seems magical, that transformation from shrew to nurturer. But it doesn’t seem to be due to conscious, maternal thoughts of her child’s love. It’s chemical, not magical. The process is instigated by the stretching of the birth canal, which causes a simple protein called oxytocin to be released in the ewe’s brain. This opens a window of a couple hours’ duration in which the ewe is open to bonding. If a lamb approaches her while that window is open, the ewe will bond with it, whether it is her baby, her neighbor’s, or a baby from the farm down the street. Then, once the oxytocin window has closed, she’ll stop bonding with new lambs. After that, if she has bonded with a lamb, she’ll continue to suckle it and to speak soothingly to it—which in sheep talk means low-pitched bleats. But she’ll be her nasty old self to all other lambs, even to her own if it didn’t approach her during the bonding window. Scientists, however, can open and close this bonding window at will, by injecting the ewe with oxytocin or inhibiting her from producing it herself. It’s like flicking a switch on a robot.
Another famous series of studies in which scientists have been able to program mammalian behavior by chemical manipulation concerns the vole, a small rodent that resembles a mouse and encompasses about 150 different species. One of those species, the prairie vole, would be a model citizen in human society. Prairie voles mate for life. They are loyal—among prairie voles whose partner disappears, for example, fewer than 30 percent will shack up with someone else.23 And they make responsible fathers—the males stick around to guard the nest and share in the parenting. Scientists study prairie voles because they are a fascinating contrast with two related species of voles, the montane vole and the meadow vole. In contrast to prairie voles, montane and meadow voles form societies of sexually promiscuous loners.24 The males of those species are, in human terms, ne’er-do-wells. They will mate with whatever female is around, then wander off and leave her to take care of the kids. If placed randomly in a large room, they avoid others of their species, preferring to crawl off to some isolated corner. (Prairie voles, on the other hand, will cluster in little chat groups.)
What is amazing about these creatures is that scientists have been able to identify the specific brain characteristic responsible for the behavioral differences among vole species, and to use that knowledge to change their behavior from that of one species to that of another. The chemical involved is again oxytocin. To have an effect on brain cells, oxytocin molecules first have to bind to receptors—specific molecules on the surface membrane of a cell. Monogamous prairie voles have many receptors for oxytocin and a related hormone called vasopressin in a particular region of the brain. A similarly high concentration of oxytocin and vasopressin receptors is found in that region of the brain in other monogamous mammals. But in promiscuous voles, there is a dearth of those receptors. And so, for example, when scientists manipulate a meadow vole’s brain to increase the number of receptors, the loner meadow vole suddenly becomes outgoing and sociable like its cousin the prairie vole.25
Unless you’re an exterminator, I’ve probably now supplied more than you need to know about prairie voles, and as for lambs, most of us never come into contact with them except those accompanied by mint jelly. But I’ve gone into detail about oxytocin and vasopressin because they play an important role in the modulation of social and reproductive behavior in mammals, including ourselves. In fact, related compounds have played a role in organisms for at least seven hundred million years, and are at work even in invertebrates such as worms and insects.26 Human social behavior is obviously more advanced and more nuanced than that of voles and sheep. Unlike them, we have ToM, and we are far more capable of overruling unconscious impulses through conscious decisions. But in humans, too, oxytocin and vasopressin regulate bonding.27 In human mothers, as in ewes, oxytocin is released during labor and delivery. It is also released in a woman when her nipples or cervix are stimulated during sexual intimacy and in both men and women when they reach sexual climax. And in both men and women, the oxytocin and vasopressin that are released into the brain after sex promote attraction and love. Oxytocin is even released during hugs, especially in women, which is why mere casual physical touch can lead to feelings of emotional closeness even in the absence of a conscious, intellectual connection between the participants.
In the broader social environment, oxytocin also promotes trust, and is produced when people have positive social contact with others.28 In one experiment, two strangers played a game in which they could cooperate to earn money. But the game was designed so that each contestant could also gain at the expense of the other. As a result, trust was an issue, and as the game progressed the players gauged each other’s character. Each assessed whether his or her partner tended to play fairly, so both players could benefit equally, or selfishly, to reap a greater benefit at his or her expense.
The unique aspect of this study was that the researchers monitored the players’ oxytocin levels by taking blood samples after they made their decisions. They found that when a player’s partner played in a manner that indicated trust, the player’s brain responded to that show of trust by releasing oxytocin. In another study, in which subjects played an investment game, investors who inhaled an oxytocin nose spray were much more likely to show trust in their partners, by investing more money with them. And when asked to categorize faces based on their expression, volunteers who were given oxytocin rated strangers as appearing more trustworthy and attractive than did other subjects not administered the drug. (Not surprisingly, oxytocin sprays are now available over the Internet, though they are not very effective unless the oxytocin is sprayed directly into the target person’s nostril.)
One of the most striking pieces of evidence of our automatic animal nature can be seen in a gene that governs vasopressin receptors in human brains. Scientists discovered that men who have two copies of a certain form of this gene have fewer vasopressin receptors, which makes them analogous to promiscuous voles. And, indeed, they exhibit the same sort of divorce and half as likely to be married as men who have more vasopressin receptors.29 So although we are much more complex in our behaviors than sheep and voles, people, too, are hardwired to certain unconscious social behaviors, a remnant of our animal past.
SOCIAL NEUROSCIENCE IS a new field, but the debate over the origin and nature of human social behavior is probably as old as human civilization itself. Philosophers of centuries past didn’t have access to studies like those of the lambs and voles; however, as long as they have speculated about the mind, they have debated the degree to which we are in conscious control of our lives.30 They used different conceptual frameworks, but observers of human behavior from Plato to Kant usually found it necessary to distinguish between direct causes of behavior—those motivations we can be in touch with through introspection—and hidden internal influences that could only be inferred.
In modern times, as I mentioned, it was Freud who popularized the unconscious. But though his theories had great prominence in clinical applications and popular culture, Freud influenced books and films more than he influenced experimental research in psychology. Through most of the twentieth century, empirical psychologists simply neglected the unconscious mind.31 Odd as it may sound today, in the first half of that century, which was dominated by those in the behaviorist movement, psychologists even sought to do away with the concept of mind altogether. They not only likened the behavior of humans to that of animals, they considered both humans and animals to be merely complex machines that responded to stimuli in predictable ways. However, though the introspection elicited by Freud and his followers is unreliable, and the inner workings of the brain were, at the time, unobservable, the idea of completely disregarding the human mind and its thought processes struck many as absurd. By the end of the 1950s the behaviorist movement had faded, and two new movements grew in its place, and flourished. One was cognitive psychology, inspired by the computer revolution. Like behaviorism, cognitive psychology generally rejected introspection. But cognitive psychology did embrace the idea that we have internal mental states such as beliefs. It treated people as information systems that process those mental states much in the way a computer processes data. The other movement was social psychology, which aimed to understand how people’s mental states are affected by the presence of others.
With these movements, psychology once again embraced the study of the mind, but both movements remained dubious about the mysterious unconscious. After all, if people are unaware of subliminal processes, and if one cannot trace them within the brain, what evidence do we have that such mental states are even real? In both cognitive and social psychology, the term “unconscious” was thus usually avoided. Still, like the therapist who doggedly brings you back again and again to the subject of your father, a handful of scientists kept doing experiments whose outcomes suggested that such processes had to be investigated, because they played such an important role in social interactions. By the 1980s, a number of now-classic experiments offered powerful evidence of the unconscious, automatic components of social behavior.
Some of those early studies of behavior drew directly on Frederic Bartlett’s memory theories. Bartlett believed that the distortions he had observed in people’s recall could be accounted for by assuming that their minds followed certain unconscious mental scripts, which were aimed at filling in gaps and making information consistent with the way they thought the world to be. Wondering whether our social behavior might also be influenced by some unconscious playbook, cognitive psychologists postulated the idea that many of our daily actions proceed according to predetermined mental “scripts”32—that they are, in fact, mindless.
In one test of that idea, an experimenter sat in a library and kept an eye on the copier. When someone approached it, the experimenter rushed up and tried to cut in front, saying, “Excuse me, I have five pages. May I use the Xerox machine?” Sure, sharing is caring, but unless the subject was making a great many more than five copies, the experimenter has provided no justification for the intrusion, so why yield? Apparently a good number of people felt that way: 40 percent of the subjects gave the equivalent of that answer, and refused. The obvious way to increase the likelihood of compliance is to offer a valid and compelling reason why someone should let you go first. And indeed, when the experimenter said, “Excuse me, I have five pages. May I use the Xerox machine, because I’m in a rush?” the rate of refusals fell radically, from 40 percent to just 6 percent. That makes sense, but the researchers suspected that something else might be going on; maybe people weren’t consciously assessing the reason and deciding it was a worthy one. Maybe they were mindlessly—automatically—following a mental script.
That script might go something like this: Someone asks a small favor with zero justification: say no; someone asks a small favor but offers a reason, any reason: say yes. Sounds like a robot or computer program, but could it apply to people? The idea is easy to test. Just walk up to people approaching a photocopier and to each of them say something like “Excuse me, I have five pages. May I use the Xerox machine, because xxx,” where “xxx” is a phrase that, though parading as the reason for the request, really provides no justification at all. The researchers chose as “xxx” the phrase “because I have to make some copies,” which merely states the obvious and does not offer a legitimate reason for butting in. If the people making copies consciously weighed this nonreason against their own needs, one would expect them to refuse in the same proportion as in the case in which no reason was offered—about 40 percent. But if the very act of giving a reason was important enough to trigger the “yes” aspect of the script, regardless of the fact that the excuse itself had no validity, only about 6 percent should refuse, as occurred in the case in which the reason provided—“I’m in a rush”—was compelling. And that’s exactly what the researchers found. When the experimenter said, “Excuse me, I have five pages. May I use the Xerox machine, because I have to make some copies?” only 7 percent refused, virtually the same number as when a valid and compelling reason was given. The lame reason swayed as many people as the legitimate one.
In their research report, those who conducted this experiment wrote that to unconsciously follow preset scripts “may indeed be the most common mode of social interaction. While such mindlessness may at times be troublesome, this degree of selective attention, of tuning the external world out, may be an achievement.” Indeed, in evolutionary terms, here is the unconscious performing its usual duty, automating tasks so as to free us to respond to other demands of the environment. In modern society, that is the essence of multitasking—the ability to focus on one task while, with the aid of automatic scripts, performing others.
Throughout the 1980s, study after study seemed to show that, because of the influence of the unconscious, people did not realize the reasons for their feelings, behavior, and judgments of other people, or how they communicated nonverbally with others. Eventually psychologists had to rethink the role of conscious thought in social interactions. And so the term “unconscious” was resurrected, though also sometimes replaced by the untainted “nonconscious,” or more specific terms like “automatic,” “implicit,” or “uncontrolled.” But these experiments were mainly clever behavioral studies, and psychologists could still only guess at the mental processes that caused the participants’ reactions. You can tell a lot about a restaurant’s recipes by sitting at a table and sampling the food, but to really know what is going on, you have to look in the kitchen, and the human brain remained hidden behind the closed doors of the skull, its inner workings virtually as inaccessible as they had been a century earlier.
THE FIRST SIGN that the brain could be observed in action came in the nineteenth century when scientists noted that nerve activity causes changes in blood flow and oxygen levels. By monitoring those levels, one could, in theory, watch a reflection of the brain at work. In his 1890 book The Principles of Psychology, William James references the work of the Italian physiologist Angelo Mosso, who recorded the pulsation of the brain in patients who had gaps in their skull following brain surgery.33 Mosso observed that the pulsation in certain regions increased during mental activity, and he speculated, correctly, that the changes were due to neuronal activity in those regions. Unfortunately, with the technology of that day, one could make such observations and measurements only if the skull was physically cut away, making the brain accessible.34 That’s not a viable strategy for studying the human brain, but that is exactly what scientists at Cambridge University did in 1899—to dogs, cats, and rabbits. The Cambridge scientists employed electric currents to stimulate various nerve pathways in each animal, then measured the brain’s response with tools applied directly to the living tissue. They showed a link between brain circulation and metabolism, but the method was both crude and cruel, and it didn’t catch on. Nor did the invention of X-rays provide an alternative, for X-rays can detect only the physical structures of the brain, not its dynamic, ever-changing electrical and chemical processes. And so for another century the working brain remained off-limits. Then, in the late 1990s, about a hundred years after Freud’s book The Interpretation of Dreams, fMRI suddenly became widely available.
As I mentioned in the Prologue, fMRI, or functional magnetic resonance imaging, is a twist on the ordinary MRI machine your doctor uses. The nineteenth-century scientists had concluded correctly that the key to identifying what part of the brain is at work at any given time is that when nerve cells are active, circulation increases, because the cells increase their consumption of oxygen. With fMRI, scientists can map oxygen consumption from outside the skull, through the quantum electromagnetic interactions of atoms within the brain. Thus fMRI allows the noninvasive three-dimensional exploration of the normal human brain in operation. It not only provides a map of the structures in the brain but indicates which among them are active at any given moment, and allows scientists to follow how the areas that are active change over time. In that way, mental processes can now be associated with specific neural pathways and brain structures.
On many occasions in the past pages I’ve said that an experimental subject’s brain had been imaged, or remarked that a particular part of the brain was or was not active in some circumstance. For example, I said that patient TN’s occipital lobe was not functioning, explained that it is the orbitofrontal cortex that is associated with the experience of pleasure, and reported that brain-imaging studies show the existence of two centers of physical pain. All these statements were made possible by the technology of fMRI. There have been other new and exciting technologies developed in recent years, but the advent of fMRI changed the way scientists study the mind, and this advance continues to play a role of unparalleled importance in basic research.
Were we sitting in front of a computer housing your fMRI data, scientists would be able to make a slice of any section of your brain, and in any orientation, and view it almost as if they had dissected the brain itself. The image above, for example, displays a slice along the brain’s central plane, as the subject engages in daydreaming. The shaded areas on the left and right indicate activity in the medial prefrontal cortex and the posterior cingulate cortex, respectively.
Courtesy of Mike Tyszka
Neuroscientists today commonly divide the brain into three crude regions, based on their function, physiology, and evolutionary development.35 In that categorization, the most primitive region is the “reptilian brain,” responsible for basic survival functions such as eating, breathing, and heart rate, and also for primitive versions of the emotions of fear and aggression that drive our fight-or-flight instincts. All vertebrate creatures—birds, reptiles, amphibians, fish, and mammals—have the reptilian brain structures.
The second region, the limbic system, is more sophisticated, the source of our unconscious social perception. It is a complex system whose definition can vary a bit from researcher to researcher, because although the original designation was anatomical, the limbic system has come to be defined instead by its function as the system in the brain instrumental in the formation of social emotions. In humans, the limbic system is often defined as a ring of structures, some of which we have already run into, including the ventromedial prefrontal cortex, dorsal anterior cingulate cortex, amygdala, hippocampus, hypothalamus, components of the basal ganglia, and, sometimes, the orbitofrontal cortex.36 The limbic system augments the reflexive reptilian emotions and is important in the genesis of social behaviors.37 Many of the structures in this second region are sometimes grouped together into what is called the “old mammalian brain,” which all mammals have, as opposed to the third region—the neocortex, or “new” mammalian brain—whose structures the more primitive mammals generally lack.
The neocortex lies above most of the limbic system.38 You may recall from Chapter 2 that it is divided into lobes and is oversized in humans. It is this gray matter that people usually think of when they talk about the brain. In Chapter 2, I talked about the occipital lobe, which is located at the back of your head and contains your visual primary processing centers. In this chapter, I’ve talked about the frontal lobe, which is, as the name indicates, located at the front.
The genus Homo, of which humans, Homo sapiens, are the only surviving species, first evolved about two million years ago. Anatomically, Homo sapiens reached its present form about two hundred thousand years ago, but as I’ve said, behaviorally, we humans did not take on our present characteristics, such as culture, until about fifty thousand years ago. In the time between the original Homo species and ourselves, the brain doubled in size. A disproportionate share of that growth occurred in the frontal lobe, and so it stands to reason that the frontal lobe is the location of some of the specific qualities that make humans human. What does this expanded structure do to enhance our survival ability to a degree that might have justified nature’s favoring it?
The frontal lobe contains regions governing the selection and execution of fine motor movements—especially of the fingers, hands, toes, feet, and tongue—that are clearly important for survival in the wild. It is interesting to note that control of the motor movements of the face is based in the frontal lobe, too. As we’ll see in Chapter 5, the fine nuances of facial expression are also crucial to survival because of the role they play in social communication. In addition to regions associated with motor movements, as I mentioned earlier, the frontal lobe contains a structure called the prefrontal cortex. “Prefrontal” means, literally, “in front of the front,” and that’s where the prefrontal cortex sits, just behind the forehead. It is in this structure that we most clearly see our humanity. The prefrontal cortex is responsible for planning and orchestrating our thoughts and actions in accordance with our goals, and integrating conscious thought, perception, and emotion; it is thought to be the seat of our consciousness.39 The ventromedial prefrontal cortex and the orbitofrontal cortex, parts of the limbic system, are subsystems within the prefrontal cortex.
Though this anatomical division of the brain into reptilian; limbic, or old mammalian; and neocortex, or new mammalian, is useful—and I’ll occasionally refer to it—it’s important to realize that it is a simplified picture. The full story is more complex. For example, the neat evolutionary steps it implies are not quite the way things happened; some so-called primitive creatures have neocortical-like tissue.40 As a result, the behavior of those animals may not be as completely instinct-driven as once thought. Also, the three discrete areas are described as almost independent, but in reality they are integrated and work in concert, with numerous neural interconnections among them. The complexity of the brain is reflected by the fact that the hippocampus alone, a tiny structure deep in the brain, is the subject of a textbook several inches thick. Another recent work, an academic article that described research on a single type of nerve cell in the hypothalamus, was over one hundred pages long and cited seven hundred intricate experiments. That’s why, despite all the research, the human mind, both conscious and unconscious, still holds enormous mystery, and why tens of thousands of scientists worldwide are still working to elucidate the function of these regions, on the molecular, cellular, neural, and psychological levels, providing ever deeper insights into how the pathways interact to produce our thoughts, feelings, and behavior.
With the advent of fMRI and the growing ability of scientists to study how different brain structures contribute to thoughts, feelings, and behavior, the two movements that followed behaviorism began to join forces. Social psychologists realized they could untangle and validate their theories of psychological processes by connecting them to their sources in the brain. Cognitive psychologists realized they could trace the origins of mental states. Also, the neuroscientists who focused on the physical brain realized they could better understand its functioning if they learned about the mental states and psychological processes the different structures produce. And so the new field of social cognitive neuroscience, or, simply, social neuroscience, emerged. It is a ménage à trois, a “household of three”: social psychology, cognitive psychology, and neuroscience. I said earlier that the first ever social neuroscience meeting took place in April 2001. To get an idea of how fast the field exploded, consider this: The first ever academic publication employing fMRI came in 1991.41 In 1992, there were only four such publications in the entire year. Even as late as 2001, an Internet search using the words “social cognitive neuroscience” yielded just 53 hits. But an identical search performed in 2007 yielded more than 30,000.42 By then, neuroscientists were turning out fMRI studies every three hours.
Today, with researchers’ new ability to watch the brain at work and to understand the origins and depth of the unconscious, the dreams of Wundt, James, and the others in the New Psychology who wanted to make that field into a rigorous experimental science are finally being realized. And though Freud’s concept of the unconscious was flawed, his stress on the importance of unconscious thought is appearing ever more valid. Vague concepts like the id and the ego have now given way to maps of brain structure, connectivity, and function. What we’ve learned is that much of our social perception—like our vision, hearing, and memory—appears to proceed along pathways that are not associated with awareness, intention, or conscious effort. How this subliminal programming affects our lives, the way we present ourselves, the way we communicate with and judge people, the way we react to social situations, and the way we think of ourselves, is the territory we are about to explore.