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 an expert would say yes or no. Eventually the novices became, like their mentors, vessels of the mysterious, ineffable expertise.
The Knowledge Gap
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 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. 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 he has played Tetris, he’ll report that he was dreaming of colorful falling blocks but will 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. 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 the way he does, you know it immediately.
One of the most impressive features of brains—and especially human brains—is the flexibility to learn almost any kind of task that comes their way. Give an apprentice the desire to impress his master in a chicken-sexing task and his brain devotes its massive resources to distinguishing males from females. Give an unemployed aviation enthusiast a chance to be a national hero and his brain learns to distinguish enemy aircraft from local flyboys. This flexibility of learning accounts for a large part of what we consider human intelligence. While many animals are properly called intelligent, humans distinguish themselves in that they are so flexibly intelligent, fashioning their neural circuits to match the task at hand. It is for this reason that we can colonize every region on the planet, learn the local language we’re born into, and master skills as diverse as playing the violin, high-jumping, and operating space shuttle cockpits.
The Liar in Your Head
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 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 leg. As a result of this apparently delusional behavior, Douglas was dismissed from his seat on the Supreme Court.
What Douglas experienced is called anosognosia. This term describes a total lack of awareness about an impairment. It’s not that Justice Douglas was lying—his brain actually believed that he could move just fine. But shouldn’t the contradicting evidence alert those with anosognosia to a problem? It turns out that alerting the system to contradictions relies on particular brain regions, especially one called the anterior cingulate cortex. Because of these conflict-monitoring regions, incompatible ideas will result in one side or another’s winning: The brain either constructs a story that makes them compatible or ignores one side of the debate. In special circumstances of brain damage, this arbitration system can be damaged, and then conflict can cause no trouble to the conscious mind.
Now Batting: Your Subconscious
On August 20, 1974, in a game between the California Angels and the Detroit Tigers, The Guinness Book of Records clocked Nolan Ryan’s fastball at 100.9 miles per hour. If you work the numbers, you’ll see that Ryan’s pitch departs the mound and crosses home plate—60 feet, 6 inches away—in four-tenths of a second. This gives just enough time for light signals from the baseball to hit the batter’s eye, work through the circuitry of the retina, activate successions of cells along the loopy superhighways of the visual system at the back of the head, cross vast territories to the motor areas, and modify the contraction of the muscles swinging the bat. Amazingly, this entire sequence is possible in less than four-tenths of a second; otherwise no one would ever hit a fastball. But even more surprising is that conscious awareness takes longer than that: about half a second. So the ball travels too rapidly for batters to be consciously aware of it.
One does not need to be consciously aware to perform sophisticated motor acts. You can notice this when you begin to duck from a snapping tree branch before you are aware that it’s coming toward you, or when you’re already jumping up when you first become aware of a phone’s ring.
Reprinted by arrangement with Pantheon Books, a division of Random House, Inc., from Incognito by David Eagleman. Copyright © 2011 by David Eagleman.