Subliminal

powerful only if the object pictured was of vital interest to the human brain. This led to an obvious category. And so when the researchers performed this experiment, they selected, for one of the static images, pornography—or, in their scientific jargon, a “highly arousing erotic image.” You can get erotica at almost any newsstand, but where do you get scientifically controlled erotica? It turns out that psychologists have a database for that. It is called the International Affective Picture System, a collection of 480 images ranging from sexually explicit material to mutilated bodies to pleasant images of children and wildlife, each categorized according to the level of arousal it produces.

As the researchers expected, when presented with unprovocative static images and asked whether the object was on the left- or the right-hand side of the photo, the subjects’ answers were correct about half the time, which is what you would expect from completely random, uninformed guesses, a rate comparable to TN’s when he was making guesses about circles versus squares. But when heterosexual male subjects were shown an image of a naked woman, they gained a significant ability to discern on which side of the image she was located, as did females who were shown images of naked men. That didn’t happen when men were shown naked men, or when women were shown naked women—with one exception, of course. When the experiment was repeated on homosexual subjects, the results flipped in the manner you might expect. The results mirrored the subjects’ sexual preferences.

Despite their successes, when asked afterward what they had seen, all the subjects described just the tedious progression of rapidly changing mosaic images the researchers had presented to their right eye. The subjects were clueless that while their conscious minds were looking at a series of snoozers, their unconscious minds were feasting on Girls (or Boys) Gone Wild. This means that while the processing of the erotic image was never delivered to the consciousness, it did register powerfully enough in the unconscious that the subjects had a subliminal awareness of it. We are reminded again of the lesson Peirce learned: We don’t consciously perceive everything that registers in our brain, so our unconscious mind may notice things that our conscious mind doesn’t. When that happens we may get a funny feeling about a business associate or a hunch about a stranger and, like Peirce, not know the source.

I learned long ago that it is often best to follow those hunches. I was twenty, in Israel just after the Yom Kippur War, and went up to visit the Golan Heights, in Israeli-occupied Syria. While hiking along a deserted road I spotted an interesting bird in a farmer’s field, and being a bird-watcher, I resolved to get a closer look. The field was ringed by a fence, which doesn’t normally deter bird-watchers, but this fence had a curious sign on it. I pondered what the sign might say. It was in Hebrew, and my Hebrew wasn’t quite good enough to decipher it. The usual message would have been “No Trespassing,” but somehow this sign seemed different. Should I stay out? Something told me yes, a something I now imagine was very much like the something that told Peirce who had stolen his watch. But my intellect, my conscious deliberative mind, said, Go ahead. Just be quick. And so I climbed the fence and walked into the field, toward the bird. Soon I heard some yelling in Hebrew, and I turned to see a man down the road on a tractor, gesturing at me in a very animated fashion. I returned to the road. It was hard to understand the man’s loud jabbering, but between my broken Hebrew and his hand gestures, I soon figured out the issue. I turned to the sign, and now realized that I did recognize those Hebrew words. The sign said, “Danger, Minefield!” My unconscious had gotten the message, but I had let my conscious mind overrule it.

It used to be difficult for me to trust my instincts when I couldn’t produce a concrete, logical basis for them, but that experience cured me. We are all a bit like patient TN, blind to certain things, being advised by our unconscious to dodge to the left and right. That advice can often save us, if we are willing to open ourselves to the input.

PHILOSOPHERS HAVE FOR centuries debated the nature of “reality,” and whether the world we experience is real or an illusion. But modern neuroscience teaches us that, in a way, all our perceptions must be considered illusions. That’s because we perceive the world only indirectly, by processing and interpreting the raw data of our senses. That’s what our unconscious processing does for us—it creates a model of the world. Or as Kant said, there is Das Ding an sich, a thing as it is, and there is Das Ding fur uns, a thing as we know it. For example, when you look around, you have the feeling that you are looking into three-dimensional space. But you don’t directly sense those three dimensions. Instead, your brain reads a flat, two-dimensional array of data from your retinas and creates the sensation of three dimensions. Your unconscious mind is so good at processing images that if you were fitted with glasses that turn the images in your eyes upside down, after a short while you would see things right side up again. If the glasses were then removed, you would see the world upside down again, but just for a while.²⁴ Because of all that processing, when we say, “I see a chair,” what we really mean is that our brain has created a mental model of a chair.

Our unconscious doesn’t just interpret sensory data, it enhances it. It has to, because the data our senses deliver is of rather poor quality and must be fixed up in order to be useful. For example, one flaw in the data your eyes supply comes from the so-called blind spot, a spot on the back of your eyeball where the wire connecting your retina and your brain is attached. This creates a dead region in each eye’s field of vision. Normally you don’t even notice it because your brain fills in the picture based on the data it gets from the surrounding area. But it is possible to design an artificial situation in which the hole becomes visible. For example, close your right eye, look at the number 1 on the right side of the line below, and move the book toward you (or away from you) until the sad face disappears—it will then be in your blind spot. Keeping your head still, now look at the 2, the 3, and so on, still with your left eye. The sad face will reappear, probably around the number 4.

To help compensate for their imperfections, your eyes change position a tiny bit several times each second. These jiggling motions are called microsaccades, to distinguish them from ordinary saccades, the larger, more rapid patterns your eyes ceaselessly follow when you study a scene. These happen to be the fastest movements executed by the human body, so rapid that they cannot be observed without special instruments. For example, as you read this text your eye is making a series of saccades along the line. And if I were talking to you, your gaze would bounce around my face, mostly near my eyes. All told, the six muscles controlling your eyeball move it some 100,000 times each day, about as many times as your heart beats.

If your eyes were a simple video camera, all that motion would make the video unwatchable. But your brain compensates by editing out the period during which your eye is in transit and filling in your perception in a way that you don’t notice. You can illustrate that edit quite dramatically, but you’ll need to enlist as your partner a good friend, or perhaps an acquaintance who has had a few glasses of wine. Here is what you do: Stand facing your partner, with about four inches separating your noses, then ask your partner to fixate midway between your eyes. Next, have your partner look toward your left ear and back. Repeat this a couple of times. Meanwhile, your job is to observe your partner’s eyes and note that you have no difficulty seeing them move back and forth. The question is, If you could stand nose to nose with yourself and repeat the procedure, would you see your own eyes move? If it is true that your brain edits out visual information received during eye movements, you would not. How can you perform this test? Stand facing a mirror, with your nose two inches from the mirror’s surface (this corresponds to four inches from a real person). Look first right between your eyes, then at your left ear, then back. Repeat a couple of times. Miraculously, you get the two views but never see your eye move between them.

Another gap in the raw data delivered by your eyes has to do with your peripheral vision, which is quite poor. In fact, if you hold your arm out and gaze at your thumbnail, the only part of your field of vision with good resolution will be the area within, and perhaps just bordering, your nail. Even if you have twenty-twenty vision, your visual acuity outside that central region will be roughly comparable to that experienced by a person who needs thick glasses and doesn’t have them. You can get a taste for that if you look at this page from a distance of a couple feet and stare at the central asterisk in the first line below (try not to cheat—it isn’t easy!). The F’s in that line are a thumbnail apart. You’ll probably be able to recognize the A and F just fine, but not much of the other letters at all. Now go down to the second line. Here, the increasing size of the letters gives you some help. But if you’re like me, you won’t be able to clearly read all the letters unless they are as large as they appear in the third line. The size of the magnification required for you to be able to see the letters at the periphery is an indication of the poor quality of your peripheral vision.

The blind spot, saccades, poor peripheral vision—all these issues should cause you severe problems. When