Subliminal

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.