So we see that different factions in the brain can get involved in the same task. In the end, it is likely that there are even more than two factions involved, all writing down information and later competing to tell the story.31 The conviction that memory is one thing is an illusion.
Here’s another example of overlapping domains. Scientists have long debated how the brain detects motion. There are many theoretical ways to build motion detectors out of neurons, and the scientific literature has proposed wildly different models that involve connections between neurons, or the extended processes of neurons (called dendrites), or large populations of neurons.32 The details aren’t important here; what’s important is that these different theories have kindled decades of debates among academics. Because the proposed models are too small to measure directly, researchers design clever experiments to support or contradict various theories. The interesting outcome has been that most of the experiments are inconclusive, supporting one model over another in some laboratory conditions but not in others. This has led to a growing recognition (reluctantly, for some) that there are many ways the visual system detects motion. Different strategies are implemented in different places in the brain. As with memory, the lesson here is that the brain has evolved multiple, redundant ways of solving problems.33 The neural factions often agree about what is out there in the world, but not always. And this provides the perfect substrate for a neural democracy.
The point I want to emphasize is that biology rarely rests with a single solution. Instead, it tends to ceaselessly reinvent solutions. But why endlessly innovate—why not find a good solution and move on? Unlike the artificial intelligence laboratory, the laboratory of nature has no master programmer who checks off a subroutine once it is invented. Once the stack block program is coded and polished, human programmers move on to the next important step. I propose that this moving on is a major reason artificial intelligence has become stuck. Biology, in contrast to artificial intelligence, takes a different approach: when a biological circuit for detect motion has been stumbled upon, there is no master programmer to report this to, and so random mutation continues to ceaselessly invent new variations in circuitry, solving detect motion in unexpected and creative new ways.
This viewpoint suggests a new approach to thinking about the brain. Most of the neuroscience literature seeks the solution to whatever brain function is being studied. But that approach may be misguided. If a space alien landed on Earth and discovered an animal that could climb a tree (say, a monkey), it would be rash for the alien to conclude that the monkey is the only animal with these skills. If the alien keeps looking, it will quickly discover that ants, squirrels, and jaguars also climb trees. And this is how it goes with clever mechanisms in biology: when we keep looking, we find more. Biology never checks off a problem and calls it quits. It reinvents solutions continually. The end product of that approach is a highly overlapping system of solutions—the necessary condition for a team-of-rivals architecture.34
THE ROBUSTNESS OF A MULTIPLE-PARTY SYSTEM
The members of a team can often disagree, but they do not have to. In fact, much of the time rivals enjoy a natural concordance. And that simple fact allows a team of rivals to be robust in the face of losing parts of the system. Let’s return to the thought experiment of a disappearing political party. Imagine that all the key decision makers of a particular party were to die in an airplane crash, and let’s consider this roughly analogous to brain damage. In many cases the loss of one party would expose the polarized, opposing opinions of a rival group—as in the case when the frontal lobes are damaged, allowing for bad behavior such as shoplifting or urinating in public. But there are other cases, perhaps much more common, in which the disappearance of a political party goes unnoticed, because all the other parties hold roughly the same opinion on some matter (for example, the importance of funding residential trash collection). This is the hallmark of a robust biological system: political parties can perish in a tragic accident and the society will still run, sometimes with little more than a hiccup to the system. It may be that for every strange clinical case in which brain damage leads to a bizarre change in behavior or perception, there are hundreds of cases in which parts of the brain are damaged with no detectable clinical sign.
An advantage of overlapping domains can be seen in the newly discovered phenomenon of cognitive reserve. 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. It’s not that cognitively fit people don’t get Alzheimer’s; it’s that their brains have protection against the symptoms. Even while parts of their brains degrade, they have other ways of solving problems. They are not stuck in the rut of having a single solution; instead, thanks to a lifetime of seeking out and building up redundant strategies, they have alternative solutions. When parts of the neural population degraded away, they were not even missed.
Cognitive reserve—and robustness in general—is achieved by blanketing a problem with overlapping solutions. As an analogy, consider a handyman. If he has several tools in his toolbox, then losing his hammer does not end his career. He can use his crowbar or the flat side of his pipe wrench. The handyman with only a couple of tools is in worse trouble.
The secret of redundancy allows us to understand what was previously a bizarre clinical mystery. Imagine that a patient sustains damage to a large chunk of her primary visual cortex, and an entire half of her visual field is now blind. You, the experimenter, pick up a cardboard shape, hold it up to her blind side, and ask her, “What do you see here?”
She says, “I have no idea—I’m blind in that half of my visual field.”
“I know,” you say. “But take a guess. Do you see a circle, square, or triangle?”
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. So removal of parts of the brain (in this case, the cortex) reveals underlying structures that do the same thing, just not as well. And from a neuroanatomical point of view, this is not surprising: after all, reptiles can see even though they have no cortex at all. They don’t see as well as we do, but they see.36
* * *
Let’s pause for a moment to consider how the team-of-rivals framework offers a different way of thinking about the brain than is traditionally taught. Many people tend to assume that the brain will be divisible into neatly labeled regions that encode, say, faces, houses, colors, bodies, tool use, religious fervor, and so on. This was the hope of the early-nineteenth-century science of phrenology, in which bumps on the skull were assumed to represent something about the size of the underlying areas. The idea was that each spot in the brain could be assigned a label on the map.
But biology rarely, if ever, pans out that way. The team-of-rivals framework presents a model of a brain that possesses multiple ways of representing the same stimulus. This view rings the death knell for the early hopes that each part of the brain serves an easily labeled function.
Note that the phrenological impulse has crept back into the picture because of our newfound power to visualize the brain with neuroimaging. Both scientists and laypeople ca
n find themselves seduced into the easy trap of wanting to assign each function of the brain to a specific location. Perhaps because of pressure for simple sound bites, a steady stream of reports in the media (and even in the scientific literature) has created the false impression that the brain area for such-and-such has just been discovered. Such reports feed popular expectation and hope for easy labeling, but the true situation is much more interesting: the continuous networks of neural circuitry accomplish their functions using multiple, independently discovered strategies. The brain lends itself well to the complexity of the world, but poorly to clear-cut cartography.
KEEPING THE UNION TOGETHER: CIVIL WARS IN THE BRAIN DEMOCRACY
In the campy cult movie Evil Dead 2, the protagonist’s right hand takes on a mind of its own and tries to kill him. The scene degenerates into a rendition of what you might find on a sixth-grade playground: the hero uses his left hand to hold back his right hand, which is trying to attack his face. Eventually he cuts off the hand with a chain saw and traps the still-moving hand under an upside-down garbage can. He stacks books on top of the can to pin it down, and the careful observer can see that the topmost book is Hemingway’s A Farewell to Arms.
As preposterous as this plotline may seem, there is, in fact, a disorder called alien hand syndrome. While it’s not as dramatic as the Evil Dead version, the idea is roughly the same. In alien hand syndrome, which can result from the split-brain surgeries we discussed a few pages ago, the two hands express conflicting desires. A patient’s “alien” hand might pick up a cookie to put it in his mouth, while the normally behaving hand will grab it at the wrist to stop it. A struggle ensues. Or one hand will pick up a newspaper, and the other will slap it back down. Or one hand will zip up a jacket, and the other will unzip it. Some patients with alien hand syndrome have found that yelling “Stop!” will cause the other hemisphere (and the alien hand) to back down. But besides that little modicum of control, the hand is running on its own inaccessible programs, and that is why it’s branded as alien—because the conscious part of the patient seems to have no predictive power over it; it does not feel as though it’s part of the patient’s personality at all. A patient in this situation often says, “I swear I’m not doing this.” Which revisits one of the main points of this book: who is the I? His own brain is doing it, not anyone else’s. It’s simply that he doesn’t have conscious access to those programs.
What does alien hand syndrome tell us? It unmasks the fact that we harbor mechanical, “alien” subroutines to which we have no access and of which we have no acquaintance. Almost all of our actions—from producing speech to picking up a mug of coffee—are run by alien subroutines, also known as zombie systems. (I use these terms interchangeably: zombie emphasizes the lack of conscious access, while alien emphasizes the foreignness of the programs.)37 Some alien subroutines are instinctual, while some are learned; all of the highly automated algorithms that we saw in Chapter 3 (serving the tennis ball, sexing the chicks) become inaccessible zombie programs when they are burned down into the circuitry. When a professional baseball player connects his bat with a pitch that is traveling too fast for his conscious mind to track, he is leveraging a well-honed alien subroutine.
Alien hand syndrome also tells us that under normal circumstances, all the automated programs are tightly controlled such that only one behavioral output can happen at a time. The alien hand highlights the normally seamless way in which the brain keeps a lid on its internal conflicts. It requires only a little structural damage to uncover what is happening beneath. In other words, keeping the union of subsystems together is not something the brain does without effort—instead, it is an active process. It is only when factions begin to secede from the union that the alienness of the parts becomes obvious.
A good illustration of conflicting routines is found in the Stroop test, a task that could hardly have simpler instructions: name the color of the ink in which a word is printed. Let’s say I present the word JUSTICE written in blue letters. You say, “Blue.” Now I show you PRINTER written in yellow. “Yellow.” Couldn’t be easier. But the trick comes when I present a word that is itself the name of a color. I present the word BLUE in the color green. Now the reaction is not so easy. You might blurt out, “Blue!”, or you might stop yourself and sputter out, “Green!” Either way, you have a much slower reaction time—and this belies the conflict going on under the hood. This Stroop interference unmasks the clash between the strong, involuntary and automatic impulse to read the word and the unusual, deliberate, and effortful task demand to state the color of the print.38
Remember the implicit association task from Chapter 3, the one that seeks to tease out unconscious racism? It pivots on the slower-than-normal reaction time when you’re asked to link something you dislike with a positive word (such as happiness). Just as with the Stroop task, there’s an underlying conflict between deeply embedded systems.
E PLURIBUS UNUM
Not only do we run alien subroutines; we also justify them. We have ways of retrospectively telling stories about our actions as though the actions were always our idea. As an example at the beginning of the book, I mentioned that thoughts come to us and we take credit for them (“I just had a great idea!”), even though our brains have been chewing on a given problem for a long time and eventually served up the final product. We are constantly fabricating and telling stories about the alien processes running under the hood.
To bring this sort of fabrication to light, we need only look at another experiment with split-brain patients. As we saw earlier, the right and left halves are similar to each other but not identical. In humans, the left hemisphere (which contains most of the capacity to speak language) can speak about what it is feeling, whereas the mute right hemisphere can communicate its thoughts only by commanding the left hand to point, reach, or write. And this fact opens the door to an experiment regarding the retrospective fabrication of stories. In 1978, researchers Michael Gazzaniga and Joseph LeDoux flashed a picture of a chicken claw to the left hemisphere of a split-brain patient and a picture of a snowy winter scene to his right hemisphere. The patient was then asked to point at cards that represented what he had just seen. His right hand pointed to a card with a chicken, and his left hand pointed to a card with a snow shovel. The experimenters asked him why he was pointing to the shovel. Recall that his left hemisphere (the one with the capacity for language), had information only about a chicken, and nothing else. But the left hemisphere, without missing a beat, fabricated a story: “Oh, that’s simple. The chicken claw goes with the chicken, and you need a shovel to clean out the chicken shed.” When one part of the brain makes a choice, other parts can quickly invent a story to explain why. If you show the command “Walk” to the right hemisphere (the one without language), the patient will get up and start walking. If you stop him and ask why he’s leaving, his left hemisphere, cooking up an answer, will say something like “I was going to get a drink of water.”
The chicken/shovel experiment led Gazzaniga and LeDoux to conclude that the left hemisphere acts as an “interpreter,” watching the actions and behaviors of the body and assigning a coherent narrative to these events. And the left hemisphere works this way even in normal, intact brains. Hidden programs drive actions, and the left hemisphere makes justifications. This idea of retrospective storytelling suggests that we come to know our own attitudes and emotions, at least partially, by inferring them from observations of our own behavior.39 As Gazzaniga put it, “These findings all suggest that the interpretive mechanism of the left hemisphere is always hard at work, seeking the meaning of events. It is constantly looking for order and reason, even when there is none—which leads it continually to make mistakes.”40
This fabrication is not limited to split-brain patients. Your brain, as well, interprets your body’s actions and builds a story around them. Psychologists have found that if you hold a pencil between your teeth while you read something, you’ll think the material is funnier; that’s becaus
e the interpretation is influenced by the smile on your face. If you sit up straight instead of slouching, you’ll feel happier. The brain assumes that if the mouth and spine are doing that, it must be because of cheerfulness.
* * *
On December 31, 1974, Supreme Court Justice William O. Douglas was debilitated by a stroke that paralyzed his left side and confined him to a wheelchair. But Justice Douglas demanded to be checked out of the hospital on the grounds that he was fine. He declared that reports of his paralysis were “a myth.” When reporters expressed skepticism, he publicly invited them to join him for a hike, a move interpreted as absurd. He even claimed to be kicking football field goals with his paralyzed side. As a result of this apparently delusional behavior, Douglas was dismissed from his bench on the Supreme Court.
What Douglas experienced is called anosognosia. This term describes a total lack of awareness about an impairment, and a typical example is a patient who completely denies their very obvious paralysis. It’s not that Justice Douglas was lying—his brain actually believed that he could move just fine. These fabrications illustrate the lengths to which the brain will go to put together a coherent narrative. When asked to place both hands on an imaginary steering wheel, a partially paralyzed and anosognosic patient will put one hand up, but not the other. When asked if both hands are on the wheel, he will say yes. When the patient is asked to clap his hands, he may move only a single hand. If asked, “Did you clap?”, he’ll say yes. If you point out that you didn’t hear any sound and ask him to do it again, he might not do it at all; when asked why, he’ll say he “doesn’t feel like it.” Similarly, as mentioned in Chapter 2, one can lose vision and claim to still be able to see just fine, even while being unable to navigate a room without crashing into the furniture. Excuses are made about poor balance, rearranged chairs, and so on—all the while denying the blindness. The point about anosognosia is that the patients are not lying, and are motivated neither by mischievousness nor by embarrassment; instead, their brains are fabricating explanations that provide a coherent narrative about what is going on with their damaged bodies.