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There is a large difference between the umwelts of humans and those of ticks and bloodhounds, but there can even be quite a bit of individual variability between humans. Most people, during some late-night departure from quotidian thinking, ask their friends the following sort of question: How do I know that what I experience as red and what you experience as red is the same thing? This is a good question, because as long as we agree on labeling some feature “red” in the outside world, it doesn’t matter if the swatch experienced by you is what I internally perceive as canary yellow. I call it red, you call it red, and we can appropriately transact over a hand of poker.
But the problem actually runs deeper. What I call vision and what you call vision might be different—mine might be upside down compared to yours, and we would never know. And it wouldn’t matter, as long as we agree on what to call things and how to point to them and where to navigate in the outside world.
This sort of question used to live in the realm of philosophical speculation, but it has now been promoted to the realm of scientific experiment. After all, across the population there are slight differences in brain function, and sometimes these translate directly into different ways of experiencing the world. And each individual believes his way is reality. To get a sense of this, imagine a world of magenta Tuesdays, tastes that have shapes, and wavy green symphonies. One in a hundred otherwise normal people experience the world this way, because of a condition called synesthesia (meaning “joined sensation”).5 In synesthetes, stimulation of a sense triggers an anomalous sensory experience: one may hear colors, taste shapes, or systematically experience other sensory blendings. For example, a voice or music may not only be heard but also seen, tasted, or felt as a touch. Synesthesia is a fusion of different sensory perceptions: the feel of sandpaper might evoke an F-sharp, the taste of chicken might be accompanied by a feeling of pinpoints on the fingertips, or a symphony might be experienced in blues and golds. Synesthetes are so accustomed to the effects that they are surprised to find that others do not share their experiences. These synesthetic experiences are not abnormal in any pathological sense; they are simply unusual in a statistical sense.
Synesthesia comes in many varieties, and having one type gives you a high chance of having a second or third type. Experiencing the days of the week in color is the most common manifestation of synesthesia, followed by colored letters and numbers. Other common varieties include tasted words, colored hearing, number lines perceived as three-dimensional forms, and letters and numerals experienced as having gender and personalities.6
Synesthetic perceptions are involuntary, automatic, and consistent over time. The perceptions are typically basic, meaning that what is sensed is something like a simple color, shape, or texture, rather than something pictorial or specific (for example, synesthetes don’t say, “This music makes me experience a vase of flowers on a restaurant table”).
Why do some people see the world this way? Synesthesia is the result of increased cross talk among sensory areas in the brain. Think of it like neighboring countries with porous borders on the brain’s map. And this cross talk results from tiny genetic changes that pass down family lineages. Think about that: microscopic changes in brain wiring can lead to different realities.7 The mere existence of synesthesia demonstrates that more than one kind of brain—and one kind of mind—is possible.
Let’s zoom in on a particular form of synesthesia as an example. For most of us, February and Wednesday do not have any particular place in space. But some synesthetes experience precise locations in relation to their bodies for numbers, time units, and other concepts involving sequence or ordinality. They can point to the spot where the number 32 is, where December floats, or where the year 1966 lies.8 These objectified three-dimensional sequences are commonly called number forms, although more precisely the phenomenon is called spatial sequence synesthesia.9 The most common types of spatial sequence synesthesia involve days of the week, months of the year, the counting integers, or years grouped by decade. In addition to these common types, researchers have encountered spatial configurations for shoe and clothing sizes, baseball statistics, historical eras, salaries, TV channels, temperature, and more. Some individuals possess a form for only one sequence; others have forms for more than a dozen. Like all synesthetes, they express amazement that not everyone visualizes sequences the way they do. If you are not synesthetic yourself, the twist is this: it is difficult for synesthetes to understand how people cope without a visualization of time. Your reality is as strange to them as theirs is to you. They accept the reality presented to them, as you do yours.10
Nonsynesthetes often imagine that sensing extra colors, textures, and spatial configurations would somehow be a perceptual burden: “Doesn’t it drive them crazy having to cope with all the extra bits?” some people ask. But the situation is no different from a color-blind person telling a person with normal vision, “You poor thing. Everywhere you look you’re always seeing colors. Doesn’t it drive you crazy to have to see everything in colors?” The answer is that colors do not drive us crazy, because seeing in color is normal to most people and constitutes what we accept as reality. In the same way, synesthetes are not driven crazy by the extra dimensions. They’ve never known reality to be anything else. Most synesthetes live their entire lives never knowing that others see the world differently than they do.
Synesthesia, in its dozens of varieties, highlights the amazing differences in how individuals subjectively see the world, reminding us that each brain uniquely determines what it perceives, or is capable of perceiving. This fact brings us back to our main point here––namely, that reality is far more subjective than is commonly supposed.11 Instead of reality being passively recorded by the brain, it is actively constructed by it.
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By analogy to your perception of the world, your mental life is built to range over a certain territory, and it is restricted from the rest. There are thoughts you cannot think. You cannot comprehend the sextillion stars of our universe, nor picture a five-dimensional cube, nor feel attracted to a frog. If these examples seem obvious (Of course I can’t!), just consider them in analogy to seeing in infrared, or picking up on radio waves, or detecting butyric acid as a tick does. Your “thought umwelt” is a tiny fraction of the “thought umgebung.” Let’s explore this territory.
The function of this wet computer, the brain, is to generate behavior that is appropriate to the environmental circumstances. Evolution has carefully carved your eyes, internal organs, sexual organs, and so on—and also the character of your thoughts and beliefs. We have not only evolved specialized immune defenses against germs, but we have also developed neural machinery to solve specialized problems that were faced by our hunter-gatherer ancestors over 99 percent of our species’ evolutionary history. The field of evolutionary psychology explores why we think in some ways and not others. While neuroscientists study the pieces and parts that make up brains, evolutionary psychologists study the software that solves social problems. In this view, the physical structure of the brain embodies a set of programs, and the programs are there because they solved a particular problem in the past. New design features are added to or discarded from the species based on their consequences.
Charles Darwin foretold this discipline in the closing of The Origin of Species: “In the distant future I see open fields for far more important researches. Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation.” In other words, our psyches evolve, just like eyes and thumbs and wings.
Consider babies. Babies at birth are not blank slates. Instead, they inherit a great deal of problem-solving equipment and arrive at many problems with solutions already at hand.12 This idea was first speculated about by Darwin (also in The Origin of Species), and later carried forward by William James in The Principles of Psychology. The concept was then ignored through most of the twentieth century. But it turned out to
be right. Babies, helpless as they are, pop into the world with neural programs specialized for reasoning about objects, physical causality, numbers, the biological world, the beliefs and motivations of other individuals, and social interactions. For example, a newborn’s brain expects faces: even when they are less than ten minutes old, babies will turn toward face-like patterns, but not to scrambled versions of the same pattern.13 By two and a half months, an infant will express surprise if a solid object appears to pass through another object, or if an object seems to disappear, as though by magic, from behind a screen. Infants show a difference in the way they treat animate versus inanimate objects, making the assumption that animate toys have internal states (intentions) that they cannot see. They also make assumptions about the intentions of adults. If an adult tries to demonstrate how to do something, a baby will impersonate him. But if the adult appears to mess up the demonstration (perhaps punctuated with a “Whoops!”) the infant will not try to impersonate what she saw, but instead what she believes the adult intended.14 In other words, by the time babies are old enough to be tested, they are already making assumptions about the workings of the world.
So although children learn by imitating what is around them—aping their parents, pets and the TV—they are not blank slates. Take babbling. Deaf children babble in the same way that hearing children do, and children in different countries sound similar even though they are exposed to radically different languages. So the initial babbling is inherited as a preprogrammed trait in humans.
Another example of preprogramming is the so-called mind-reading system—this is the collection of mechanisms by which we use the direction and movement of other people’s eyes to infer what they want, know, and believe. For example, if someone abruptly looks over your left shoulder, you’ll immediately suppose there is something interesting going on behind you. Our gaze-reading system is fully in place early in infancy. In conditions like autism this system can be impaired. On the flip side, it can be spared even while other systems are damaged, as in a disorder called Williams syndrome, in which gaze reading is fine but social cognition is broadly deficient in other ways.
Prepackaged software can circumvent the explosion of possibilities that a blank-slate brain would immediately run up against. A system that begins with a blank slate would be unable to learn all the complex rules of the world with only the impoverished input that babies receive.15 It would have to try everything, and it would fail. We know this, if for no other reason, than from the long history of failure of artificial neural networks that start off knowledge-free and attempt to learn the rules of the world.
Our preprogramming is deeply involved in social exchange—the way humans interact with one another. Social interaction has been critical to our species for millions of years, and as a result the social programs have worked their way deep down into the neural circuitry. As the psychologists Leda Cosmides and John Tooby put it, “The heartbeat is universal because the organ that generates it is everywhere the same. This is a parsimonious explanation for the universality of social exchange as well.” In other words, the brain, like the heart, doesn’t require a particular culture in order to express social behavior—that program comes pre-bundled with the hardware.
Let’s turn to a particular example: your brain has trouble with certain types of calculations that it did not evolve to solve, but has an easy time with calculations that involve social issues. Say I show you the four cards below and assert the following claim: If a card has an even number on one face, it has the name of a primary color on its opposite face. Which two cards do you need to turn over to assess whether I’m telling you the truth?
Don’t worry if this problem gives you trouble: it’s difficult. The answer is that you need to turn over only the number 8 card and the Purple card. If you had turned over the 5 card and found Red on the other side, that would tell you nothing about the truth of the rule, because I made a statement only about even-numbered cards. Likewise, if you’d turned over the Red card and found an odd number on the other side, it would also have no bearing on the logical rule I gave you, because I never specified what odd numbers may have on their other side.
If your brain were wired up for the rules of conditional logic, you would have no problem with this task. But less than a quarter of people get it right, and that’s true even if they’ve had formal training in logic.16 The fact that the problem is found to be difficult indicates that our brains aren’t wired for general logic problems of this sort. Presumably this is because we have gotten by decently well as a species without needing to nail these sorts of logic puzzles.
But here’s the twist to the story. If the exact same logic problem is presented in a way that we are hardwired to understand—that is, cast in the vocabulary of things a social human brain cares about—then it is solved easily.17 Suppose the new rule is this: If you’re under 18, you cannot drink alcohol. Now each card, as shown below, has the age of a person on one side and the drink they’re holding on the other.
Which cards do you need to turn over to see if the rule is being broken? Here, most participants get it right (the 16 and Tequila cards). Note that the two puzzles are formally equivalent. So why did you find the first one difficult and the second one easier? Cosmides and Tooby argue that the performance boost in the second case represents a neural specialization. The brain cares about social interaction so much that it has evolved special programs devoted to it: primitive functions to deal with issues of entitlement and obligation. In other words, your psychology has evolved to solve social problems such as detecting cheaters—but not to be smart and logical in general.
MANTRA OF THE EVOLVING BRAIN: BURN REALLY GOOD PROGRAMS ALL THE WAY DOWN TO THE DNA
“In general, we’re least aware of what our minds do best.”
—Marvin Minsky, The Society of Mind
Instincts are complex, inborn behaviors that do not have to be learned. They unpack themselves more or less independently of experience. Consider the birth of a horse: it drops out of the mother’s womb, rights itself onto its skinny, uncertain legs, wobbles around for a bit, and finally begins to walk and run, following the rest of the herd in a matter of minutes to hours. The foal is not learning to use its legs from years of trial and error, as a human infant does. Instead, the complex motor action is instinctual.
Because of specialized neural circuits that come as standard equipment with brains, frogs are mad with desire for other frogs and cannot imagine what it would mean for a human to command sex appeal—and vice versa. The programs of instinct, carved by the pressures of evolution, keep our behaviors running smoothly and steer our cognition with a firm hand.
Instincts are traditionally thought to be the opposite of reasoning and learning. If you’re like most people, you’ll consider your dog to operate largely on instincts, while humans appear to run on something other than instincts—something more like reason. The great nineteenth-century psychologist William James was the first to get suspicious of this story. And not just suspicious: he thought it was dead wrong. He suggested instead that human behavior may be more flexibly intelligent than that of other animals because we possess more instincts than they do, not fewer. These instincts are tools in the toolbox, and the more you have, the more adaptable you can be.
We tend to be blind to the existence of these instincts precisely because they work so well, processing information effortlessly and automatically. Just like the unconscious software of the chicken sexers or plane spotters or tennis players, the programs are burned down so deeply into the circuitry that we can no longer access them. Collectively, these instincts form what we think of as human nature.18
Instincts differ from our automatized behaviors (typing, bicycle riding, serving a tennis ball) in that we didn’t have to learn them in our lifetime. We inherited them. Our innate behaviors represent ideas so useful that they became encoded into the tiny, cryptic language of DNA. This was accomplished by natural selection over millions of years: those who possessed inst
incts that favored survival and reproduction tended to multiply.
The key point here is that the specialized, optimized circuitry of instinct confers all the benefits of speed and energy efficiency, but at the cost of being further away from the reach of conscious access. As a result, we have as little access to our hardwired cognitive programs as we do to our tennis serve. This situation leads to what Cosmides and Tooby call “instinct blindness”: we are not able to see the instincts that are the very engines of our behavior.19 These programs are inaccessible to us not because they are unimportant, but because they’re critical. Conscious meddling would do nothing to improve them.
William James realized the hidden nature of instincts and suggested that we coax instincts into the light by a simple mental exercise: try to make the “natural seem strange” by asking “the why of any instinctive human act”:
Why do we smile, when pleased, and not scowl? Why are we unable to talk to a crowd as we talk to a single friend? Why does a particular maiden turn our wits so upside-down? The common man can only say, Of course we smile, of course our heart palpitates at the sight of the crowd, of course we love the maiden, that beautiful soul clad in that perfect form, so palpably and flagrantly made for all eternity to be loved!
And so, probably, does each animal feel about the particular things it tends to do in the presence of particular objects.… To the lion it is the lioness which is made to be loved; to the bear, the she-bear. To the broody hen the notion would probably seem monstrous that there should be a creature in the world to whom a nestful of eggs was not the utterly fascinating and precious and never-to-be-too-much-sat-upon object which it is to her.