This predictability that you develop between your own actions and the resulting sensations is the reason you cannot tickle yourself. Other people can tickle you because their tickling maneuvers are not predictable to you. And if you’d really like to, there are ways to take predictability away from your own actions so that you can tickle yourself. Imagine controlling the position of a feather with a time-delay joystick: when you move the stick, at least one second passes before the feather moves accordingly. This takes away the predictability and grants you the ability to self-tickle. Interestingly, schizophrenics can tickle themselves because of a problem with their timing that does not allow their motor actions and resulting sensations to be correctly sequenced.47
Recognizing the brain as a loopy system with its own internal dynamics allows us to understand otherwise bizarre disorders. Take Anton’s syndrome, a disorder in which a stroke renders a person blind—and the patient denies her blindness.48 A group of doctors will stand around the bedside and say, “Mrs. Johnson, how many of us are around your bed?” and she’ll confidently answer, “Four,” even though in fact there are seven of them. A doctor will say, “Mrs. Johnson, how many fingers am I holding up?” She’ll say, “Three,” while in fact he is holding up none. When he asks, “What color is my shirt?” she’ll tell him it is white when it is blue. Those with Anton’s syndrome are not pretending they are not blind; they truly believe they are not blind. Their verbal reports, while inaccurate, are not lies. Instead, they are experiencing what they take to be vision, but it is all internally generated. Often a patient with Anton’s syndrome will not seek medical attention for a little while after the stroke, because she has no idea she is blind. It is only after bumping into enough furniture and walls that she begins to feel that something is amiss. While the patient’s answers seem bizarre, they can be understood as her internal model: the external data is not getting to the right places because of the stroke, and so the patient’s reality is simply that which is generated by the brain, with little attachment to the real world. In this sense, what she experiences is no different from dreaming, drug trips, or hallucinations.
HOW FAR IN THE PAST DO YOU LIVE?
It is not only vision and hearing that are constructions of the brain. The perception of time is also a construction.
When you snap your fingers, your eyes and ears register information about the snap, which is processed by the rest of the brain. But signals move fairly slowly in the brain, millions of times more slowly than electrons carrying signals in copper wire, so neural processing of the snap takes time. At the moment you perceive it, the snap has already come and gone. Your perceptual world always lags behind the real world. In other words, your perception of the world is like a “live” television show (think Saturday Night Live), which is not actually live. Instead, these shows are aired with a delay of a few seconds, in case someone uses inappropriate language, hurts himself, or loses a piece of clothing. And so it is with your conscious life: it collects a lot of information before it airs it live.49
Stranger still, auditory and visual information are processed at different speeds in the brain; yet the sight of your fingers and the sound of the snap appear simultaneous. Further, your decision to snap now and the action itself seem simultaneous with the moment of the snap. Because it’s important for animals to get timing right, your brain does quite a bit of fancy editing work to put the signals together in a useful way.
The bottom line is that time is a mental construction, not an accurate barometer of what’s happening “out there.” Here’s a way to prove to yourself that something strange is going on with time: look at your own eyes in a mirror and move your point of focus back and forth so that you’re looking at your right eye, then at your left eye, and back again. Your eyes take tens of milliseconds to move from one position to the other, but—here’s the mystery—you never see them move. What happens to the gaps in time while your eyes are moving? Why doesn’t your brain care about the small absences of visual input?
And the duration of an event—how long it lasted—can be easily distorted as well. You may have noticed this upon glancing at a clock on the wall: the second hand seems to be frozen for slightly too long before it starts ticking along at its normal pace. In the laboratory, simple manipulations reveal the malleability of duration. For example, imagine I flash a square on your computer screen for half a second. If I now flash a second square that is larger, you’ll think the second one lasted longer. Same if I flash a square that’s brighter. Or moving. These will all be perceived to have a longer duration than the original square.50
As another example of the strangeness of time, consider how you know when you performed an action and when you sensed the consequences. If you were an engineer, you would reasonably suppose that something you do at timepoint 1 would result in sensory feedback at timepoint 2. So you would be surprised to discover that in the lab we can make it seem to you as though 2 happens before 1. Imagine that you can trigger a flash of light by pressing a button. Now imagine that we inject a slight delay—say, a tenth of a second—between your press and the consequent flash. After you’ve pressed the button several times, your brain adapts to this delay, so that the two events seem slightly closer in time. Once you are adapted to the delay, we surprise you by presenting the flash immediately after you press the button. In this condition, you will believe the flash happened before your action: you experience an illusory reversal of action and sensation. The illusion presumably reflects a recalibration of motor-sensory timing which results from a prior expectation that sensory consequences should follow motor acts without delay. The best way to calibrate timing expectations of incoming signals is to interact with the world: each time a person kicks or knocks on something, the brain can make the assumption that the sound, sight, and touch should be simultaneous. If one of the signals arrives with a delay, the brain adjusts its expectations to make it seem as though both events happened closer in time.
Interpreting the timing of motor and sensory signals is not merely a party trick of the brain; it is critical to solving the problem of causality. At bottom, causality requires a temporal order judgment: did my motor act precede or follow the sensory input? The only way this problem can be accurately solved in a multisensory brain is by keeping the expected time of signals well calibrated, so that “before” and “after” can be accurately determined even in the face of different sensory pathways of different speeds.
Time perception is an active area of investigation in my laboratory and others, but the overarching point I want to make here is that our sense of time—how much time passed and what happened when—is constructed by our brains. And this sense is easily manipulated, just like our vision can be.
So the first lesson about trusting your senses is: don’t. Just because you believe something to be true, just because you know it’s true, that doesn’t mean it is true. The most important maxim for fighter pilots is “Trust your instruments.” This is because your senses will tell you the most inglorious lies, and if you trust them—instead of your cockpit dials—you’ll crash. So the next time someone says, “Who are you going to believe, me or your lying eyes?”, consider the question carefully.
After all, we are aware of very little of what is “out there.” The brain makes time-saving and resource-saving assumptions and tries to see the world only as well as it needs to. And as we realize that we are not conscious of most things until we ask ourselves questions about them, we have taken the first step in the journey of self-excavation. We see that what we perceive in the outside world is generated by parts of the brain to which we do not have access.
These principles of inaccessible machinery and rich illusion do not apply only to basic perceptions of vision and time. They also apply at higher levels—to what we think and feel and believe—as we shall see in the next chapter.
A hint allows the image to take on meaning as a bearded figure. The light patterns hitting your eyes are generally insufficient for vision in the absen
ce of expectations.
*Consider the analogous question of knowing whether your refrigerator light is always on. You might erroneously conclude that it is, simply because it appears that way every time you sneak up to the refrigerator door and yank it open.
**If you haven’t spotted it yet, the change in the figure is the height of the wall behind the statue.
Mind: The Gap
“I cannot grasp all that I am”
—Augustine
CHANGING LANES
There is a looming chasm between what your brain knows and what your mind is capable of accessing. Consider the simple act of changing lanes while driving a car. Try this: close your eyes, grip an imaginary steering wheel, and go through the motions of a lane change. Imagine that you are driving in the left lane and you would like to move over to the right lane. Before reading on, actually put down the book and try it. I’ll give you 100 points if you can do it correctly.
It’s a fairly easy task, right? I’m guessing that you held the steering wheel straight, then banked it over to the right for a moment, and then straightened it out again. No problem.
Like almost everyone else, you got it completely wrong.1 The motion of turning the wheel rightward for a bit, then straightening it out again would steer you off the road: you just piloted a course from the left lane onto the sidewalk. The correct motion for changing lanes is banking the wheel to the right, then back through the center, and continuing to turn the wheel just as far to the left side, and only then straightening out. Don’t believe it? Verify it for yourself when you’re next in the car. It’s such a simple motor task that you have no problem accomplishing it in your daily driving. But when forced to access it consciously, you’re flummoxed.
The lane-changing example is one of a thousand. You are not consciously aware of the vast majority of your brain’s ongoing activities, and nor would you want to be—it would interfere with the brain’s well-oiled processes. The best way to mess up your piano piece is to concentrate on your fingers; the best way to get out of breath is to think about your breathing; the best way to miss the golf ball is to analyze your swing. This wisdom is apparent even to children, and we find it immortalized in poems such as “The Puzzled Centipede”:
A centipede was happy quite,
Until a frog in fun
Said, “Pray tell which leg comes after which?”
This raised her mind to such a pitch,
She lay distracted in the ditch
Not knowing how to run.
The ability to remember motor acts like changing lanes is called procedural memory, and it is a type of implicit memory—meaning that your brain holds knowledge of something that your mind cannot explicitly access.2 Riding a bike, tying your shoes, typing on a keyboard, or steering your car into a parking space while speaking on your cell phone are examples of this. You execute these actions easily, but without knowing the details of how you do it. You would be totally unable to describe the perfectly timed choreography with which your muscles contract and relax as you navigate around other people in a cafeteria while holding a tray, yet you have no trouble doing it. This is the gap between what your brain can do and what you can tap into consciously.
The concept of implicit memory has a rich, if little known, tradition. By the early 1600s, René Descartes had already begun to suspect that although experience with the world is stored in memory, not all memory is accessible. The concept was rekindled in the late 1800s by the psychologist Hermann Ebbinghaus, who wrote that “most of these experiences remain concealed from consciousness and yet produce an effect which is significant and which authenticates their previous experience.”3
To the extent that consciousness is useful, it is useful in small quantities, and for very particular kinds of tasks. It’s easy to understand why you would not want to be consciously aware of the intricacies of your muscle movement, but this can be less intuitive when applied to your perceptions, thoughts and beliefs, which are also final products of the activity of billions of nerve cells. We turn to these now.
THE MYSTERY OF THE CHICKEN SEXERS AND THE PLANE SPOTTERS
The best chicken sexers in the world hail from Japan. When chicken hatchlings are born, large commercial hatcheries usually set about dividing them into males and females, and the practice of distinguishing the two genders is known as chick sexing. Sexing is necessary because the two genders receive different feeding programs: one for the females, who will eventually produce eggs, and another for the males, who are typically destined to be disposed of because of their uselessness in the commerce of producing eggs; only a few males are kept and fattened for meat. So the job of the chick sexer is to pick up each hatchling and quickly determine its sex in order to choose the correct bin to put it in. The problem is that the task is famously difficult: male and female chicks look exactly alike.
Well, almost exactly. The Japanese invented a method of sexing chicks known as vent sexing, by which expert chicken sexers could rapidly ascertain the sex of one-day-old hatchlings. Beginning in the 1930s, poultry breeders from around the world traveled to the Zen-Nippon Chick Sexing School in Japan to learn the technique.
The mystery was that no one could explain exactly how it was done.4 It was somehow based on very subtle visual cues, but the professional sexers could not report what those cues were. Instead, they would look at the chick’s rear (where the vent is) and simply seem to know the correct bin to throw it in.
And this is how the professionals taught the student sexers. The master would stand over the apprentice and watch. The students would pick up a chick, examine its rear, and toss it into one bin or the other. The master would give feedback: yes or no. After weeks on end of this activity, the student’s brain was trained up to masterful—albeit unconscious—levels.
Meanwhile, a similar story was unfolding oceans away. During World War II, under constant threat of bombings, the British had a great need to distinguish incoming aircraft quickly and accurately. Which aircraft were British planes coming home and which were German planes coming to bomb? Several airplane enthusiasts had proved to be excellent “spotters,” so the military eagerly employed their services. These spotters were so valuable that the government quickly tried to enlist more spotters—but they turned out to be rare and difficult to find. The government therefore tasked the spotters with training others. It was a grim attempt. The spotters tried to explain their strategies but failed. No one got it, not even the spotters themselves. Like the chicken sexers, the spotters had little idea how they did what they did—they simply saw the right answer.
With a little ingenuity, the British finally figured out how to successfully train new spotters: by trial-and-error feedback. A novice would hazard a guess and the expert would say yes or no. Eventually the novices became, like their mentors, vessels of the mysterious, ineffable expertise.5
There can be a large gap between knowledge and awareness. When we examine skills that are not amenable to introspection, the first surprise is that implicit memory is completely separable from explicit memory: you can damage one without hurting the other. Consider patients with anterograde amnesia, who cannot consciously recall new experiences in their lives. If you spend an afternoon trying to teach them the video game Tetris, they will tell you the next day that they have no recollection of the experience, that they have never seen this video game before, and, most likely, that they have no idea who you are, either. But if you look at their performance on the game the next day, you’ll find that they have improved exactly as much as nonamnesiacs.6 Implicitly their brains have learned the game—the knowledge is simply not accessible to their consciousness. (Interestingly, if you wake up an amnesic patient during the night after they’ve played Tetris, they’ll report that they were dreaming of colorful falling blocks, but they have no idea why.)
Of course, it’s not just sexers and spotters and amnesiacs who enjoy unconscious learning: essentially everything about your interaction with the world rests on this process.7 You may have a
difficult time putting into words the characteristics of your father’s walk, or the shape of his nose, or the way he laughs—but when you see someone who walks, looks, or laughs like him, you know it immediately.
HOW TO KNOW IF YOU’RE A RACIST
We often do not know what’s buried in the caverns of our unconscious. An example of this comes up, in its ugliest form, with racism.
Consider this situation: A white company owner refuses employment to a black applicant, and the case goes to court. The employer insists that he harbors no racism; the applicant insists otherwise. The judge is stuck: how can one ever know what sort of biases may lurk in someone’s unconscious, modulating their decisions, even if they are not aware of it consciously? People don’t always speak their minds, in part because people don’t always know their minds. As E. M. Forster quipped: “How do I know what I think until I hear what I say?”
But if someone is unwilling to say something, are there ways of probing what is in the unconscious brain? Are there ways to ferret out subterranean beliefs by observing someone’s behavior?