Incognito: The Secret Lives of the Brain

by David Eagleman

most of what we do and think and feel is not under our conscious control.

As Carl Jung put it, “In each of us there is another whom we do not know.” As Pink Floyd put it, “There’s someone in my head, but it’s not me.”

The brain generally does not need to know most things; it merely knows how to go out and retrieve the data. It computes on a need-to-know basis.

You’re not perceiving what’s out there. You’re perceiving whatever your brain tells you.

awareness of your surroundings occurs only when sensory inputs violate expectations.

The magnetic power of unconscious self-love goes beyond what and whom you prefer. Incredibly, it can subtly influence where you live and what you do, as well.

Implicit egotism can also influence what you chose to do with your life. By analyzing professional membership directories, Pelham and his colleagues found that people named Denise or Dennis are disproportionately likely to become dentists, while people named Laura or Lawrence are more likely to become lawyers, and people with names like George or Georgina to become geologists.

It will come as no surprise to you that the mere exposure effect is part of the magic behind product branding, celebrity building, and political campaigning: with repeated exposure to a product or face, you come to prefer it more.

The illusion-of-truth effect highlights the potential danger for people who are repeatedly exposed to the same religious edicts or political slogans.

This led Damasio to propose that the feelings produced by physical states of the body come to guide behavior and decision making.25 Body states become linked to outcomes of events in the world. When something bad happens, the brain leverages the entire body (heart rate, contraction of the gut, weakness of the muscles, and so on) to register that feeling, and that feeling becomes associated with the event. When the event is next pondered, the brain essentially runs a simulation, reliving the physical feelings of the event. Those feelings then serve to navigate, or at least bias, subsequent decision making. If the feelings from a given event are bad, they dissuade the action; if they are good, they encourage it.

11 Instead of reality being passively recorded by the brain, it is actively constructed by it.

Recently, evolutionary psychologists have turned their sights on love and divorce. It didn’t take them long to notice that when people fall in love, there’s a period of up to three years during which the zeal and infatuation ride at a peak. The internal signals in the body and brain are literally a love drug. And then it begins to decline. From this perspective, we are preprogrammed to lose interest in a sexual partner after the time required to raise a child has passed—which is, on average, about four years.40

The unexpected part of the news is that the conscious you is the smallest bit-player in the brain. It is something like a young monarch who inherits the throne and takes credit for the glory of the country—without ever being aware of the millions of workers who keep the place running.

the Greek poet Alcaeus of Mytilene coined a popular phrase En oino álétheia (In wine there is the truth), which was repeated by the Roman Pliny the Elder as In vino veritas.

Consider this simple experiment with a laboratory rat: if you put both food and an electrical shock at the end of an alley, the rat finds himself stuck at a certain distance from the end. He begins to approach but withdraws; he begins to withdraw but finds the courage to approach again. He oscillates, conflicted.8 If you outfit the rat with a little harness to measure the force with which he pulls toward food alone and, separately, you measure the force with which he pulls away from an electric shock alone, you find that the rat gets stuck at the point where the two forces are equal and cancel out. The pull matches the push. The perplexed rat has two pair of paws on his steering wheel, each pulling in opposite directions—and as a result he cannot get anywhere. Brains—whether rat or human—are machines made of conflicting parts.

Freely made decisions that bind you in the future are what philosophers call a Ulysses contract.25 As a concrete example, one of the first steps in breaking an alcohol addiction is to ensure, during sober reflection, that there is no alcohol in the house. The temptation will simply be too great after a stressful workday or on a festive Saturday or a lonely Sunday.

The fact that the two halves are doubles of the same basic plan is evidenced by a type of surgery called a hemispherectomy, in which one entire half of the brain is removed (this is done to treat intractable epilepsy caused by Rasmussen’s encephalitis). Amazingly, as long as the surgery is performed on a child before he is about eight years old, the child is fine. Let me repeat that: the child, with only half his brain remaining, is fine. He can eat, read, speak, do math, make friends, play chess, love his parents, and everything else that a child with two hemispheres can do.

Many people are found to have the neural ravages of Alzheimer’s disease upon autopsy—but they never showed the symptoms while they were alive. How can this be? It turns out that these people continued to challenge their brains into old age by staying active in their careers, doing crossword puzzles, or carrying out any other activities that kept their neural populations well exercised. As a result of staying mentally vigorous, they built what neuropsychologists call cognitive reserve.

She says, “I really can’t tell you. I don’t see anything at all. I’m blind there.” You say, “I know, I know. But guess.” Finally, with exasperation, she guesses that the shape is a triangle. And she’s correct, well above what random chance would predict.35 Even though she’s blind, she can tease out a hunch—and this indicates that something in her brain is seeing. It’s just not the conscious part that depends on the integrity of her visual cortex. This phenomenon is called blindsight, and it teaches us that when conscious vision is lost, there are still subcortical factory workers behind the scenes running their normal programs.

As the French essayist Michel de Montaigne put it, “There is as much difference between us and ourselves as there is between us and others.”

Physicians now watch out for these behavioral changes as a possible side effect of dopamine drugs like pramipexole, and a warning is clearly listed on the label. When a gambling situation crops up, families and caretakers are instructed to secure the credit cards of the patient and carefully monitor their online activities and local trips.

SENTENCING BASED ON MODIFIABILITY Personalization of the law can go in many directions; I’ll suggest one here. Let’s return to the case of your daughter writing with a crayon on the wall. In one scenario, she’s doing it mischievously; in the other, while she’s sleepwalking. Your intuition tells you that you would punish only for the awake case and not for the asleep case. But why? I propose that your intuition may incorporate an important insight about the purpose of punishment. In this case, what matters is not so much your intuition about blameworthiness (although she is clearly not blameworthy when she’s asleep), but instead about modifiability. The idea would be to punish only when the behavior is modifiable. She cannot modify her behavior in the case of sleepwalking, and therefore punishment would be cruel and fruitless.

Consider, for example, that all known serial murderers were abused as children.39 Does this make them less blameworthy? Who cares? It’s the wrong question to ask. The knowledge that they were abused encourages us to prevent child abuse, but it does nothing to change the way we deal with the particular serial murderer standing in front of the bench.

On February 28, 1571, on the morning of his thirty-eighth birthday, the French essayist Michel de Montaigne decided to make a radical change in his life’s trajectory. He quit his career in public life, set up a library with one thousand books in a tower at the back of his large estate, and spent the rest of his life writing essays about the complex, fleeting, protean subject that interested him the most: himself. His first conclusion was that a search to know oneself is a fool’s errand, because the self continuously changes and keeps ahead of a firm description. That didn’t stop him from searching, however, and his question has resonated through the centuries: Que sais-je? (What do I know?)

Consider the powerful effects of the small molecules we call narcotics. These molecules alter consciousness, affect cognition, and navigate behavior. We are slave to these molecules. Tobacco, alcohol, and cocaine are self-administered universally for the purpose of mood changing. If we knew nothing else about neurobiology, the mere existence of narcotics would give us all the evidence we require that our behavior and psychology can be commandeered at the molecular level.

Some fraction of history’s prophets, martyrs, and leaders appear to have had temporal lobe epilepsy.11 Consider Joan of Arc, the sixteen-year-old-girl who managed to turn the tide of the Hundred Years War because she believed (and convinced the French soldiers) that she was hearing voices from Saint Michael the archangel, Saint Catherine of Alexandria, Saint Margaret, and Saint Gabriel. As she described her experience, “When I was thirteen, I had a voice from God to help me to govern myself. The first time, I was terrified. The voice came to me about noon: it was summer, and I was in my father’s garden.” Later she reported, “Since God had commanded me to go, I must do it. And since God had commanded it, had I had a hundred fathers and a hundred mothers, and had I been a king’s daughter, I would have gone.”

A third example comes from the observation that smoking cannabis (marijuana) as a teenager increases the probability of developing psychosis as an adult. But this connection is true only for some people, and not for others. By this point, you can guess the punch line: a genetic variation underlies one’s susceptibility to this. With one combination of alleles, there is a strong link between cannabis use and adult psychosis; with a different combination, the link is weak.

The brain presumably does not break the laws of physics, but that does not mean that equations describing detailed biochemical interactions will amount to the correct level of description. As the complexity theorist Stuart Kauffman puts it, “A couple in love walking along the banks of the Seine are, in real fact, a couple in love walking along the banks of the Seine, not mere particles in motion.”