Livewired. David Eagleman
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interesting in recent years: when new occupants move into the visual cortex, they retain some of the former architecture—like the mosques in Turkey that used to be Roman cathedrals. As an example, the area that processes visual written language in the sighted is the same area that becomes active when the blind read Braille.21 Similarly, the main area for processing visual motion in the sighted is activated for tactile motion in the blind (for example, something moving across the fingertips or the tongue).22 The main neural network involved in visual object recognition in the sighted is activated by touch in the blind.23 Such observations have led to the hypothesis that the brain is a “task machine”—doing jobs like detecting motion or objects in the world—rather than a system organized by particular senses.24 In other words, brain regions care about solving certain types of tasks, irrespective of the sensory channel by which information arrives.
There’s a side note here that we’ll return to in later chapters: age matters. In those born blind, their occipital cortex is completely taken over by other senses. If a person goes blind at an early age—say, at five years old—the takeover is less comprehensive. For the “late blind” (those who lost vision after the age of ten), the cortical takeovers are even smaller. The older the brain, the less flexible it is for redeployment, just as North American borders now shift very little after settling into place for five centuries.
The same thing we see with the loss of vision happens with the loss of any sense. For example, in the deaf, the auditory cortex becomes employed for vision and other tasks.25 Just as Lord Nelson’s loss of a limb led to cortical takeovers by neighboring territories, so too does the loss of hearing, smell, taste, or anything else. The cartography of the brain constantly shifts to best represent the incoming data.26
Once you begin looking for it, you’ll see this competition for territory everywhere around you. Think of an airport in a major city. If there are a large number of incoming flights from a particular airline (United), and fewer flights from another (Delta), then it would be no surprise to see the number of United counters grow, while those from Delta shrink. United would take over more of the gates, more of the baggage claims, and more space on the monitors. If another airline went fully out of business (think Trans World Airlines), then all of its presence in the airport would be quickly taken over. And so it goes with the brain and its sensory inputs.
Now we understand how competition leads to takeover. But all this leads to a question: When a sense captures more area, does that give it greater capabilities?
THE MORE THE BETTER
A young boy named Ronnie was born in Robbinsville, North Carolina. Soon after he was born, it became clear he was blind. At one year and one day old, his mother abandoned him, citing that his blindness was her punishment from God. He was raised in poverty by his grandparents until he was five, then sent off to a school for the sightless.
When he was six years old, his mother came by, just once. She had another child now, a girl. His mother said, “Ron, I want you to feel her eyes. You know, her eyes are so pretty. She did not shame me the way that you did. She can see.” That was the last time he ever had contact with his mother.
As hard as his childhood was, it became clear that Ronnie had a gift for music. His instructors spotted his talents, and Ronnie began to formally study classical music. One year after he picked up the violin, his teachers declared him a virtuoso. He went on to master piano, guitar, and several other string and woodwind instruments.
From there he went on to become one of the most popular performers of his day, locking down both pop music and country-western markets. He secured forty country hits at the number-one slot. He earned six Grammy Awards.
Ronnie Milsap is just one of many blind musicians; others include Andrea Bocelli, Ray Charles, Stevie Wonder, Diane Schuur, José Feliciano, and Jeff Healey. Their brains have learned to rely on the signals of sound and touch in their environment, and they become better at processing those than sighted people.
While musical stardom is not guaranteed for blind people, brain reorganization is. As a result, perfect musical pitch is overrepresented in the blind, and blind people are up to ten times better at determining whether a musical pitch subtly wobbles up or down.27 They simply have more brain territory devoted to the task of listening. In a recent experiment, participants who were sighted or blind had one ear plugged up and were then asked to point to the locations of sounds in the room. Because pinpointing a sound requires a comparison of the signals at both ears, it was expected that everyone would fail miserably at this task. And that’s what happened with the sighted participants. But the blind participants were able to generally tell where the sounds were positioned.28 Why? Because the exact shape of the cartilage of the outer ear (even just one ear) bounces sounds around in subtle ways that give clues to location—but only if one is highly attuned to pick up on those signals. The sighted have less cortex devoted to sound, and so their ability to extract subtle sound information is underdeveloped.
This sort of extreme talent with sound is common among the blind. Take Ben Underwood. When he was two years old, Ben stopped seeing out of his left eye. His mother took him to the doctor and soon discovered he had retinal cancer in both eyes. After chemotherapy and radiation failed, surgeons removed both his eyes. But by the time Ben was seven years old, he had devised a useful, unexpected technique: he clicked with his mouth and listened for the returning echoes. By this method, he could determine the locations of open doorways, people, parked cars, garbage cans, and so on. He was echolocating: bouncing his sound waves off objects in the environment and listening to what returned.29
A documentary about Ben kicked off with the statement that he was “the only person in the world who can see with echolocation.”30 The statement was erroneous in a couple of ways. First, Ben may or may not have seen the way a sighted person would think of sight; all we know is that his brain was able to convert sound waves into some practical understanding of the large objects in front of him. But more on that later.
Second, and more important, Ben was not the only one using echo-location: thousands of blind people have done so.31 In fact, the phenomenon has been discussed since at least the 1940s, when the word “echolocation” was first coined in a Science article titled “Echolocation by Blind Men, Bats, and Radar.”32 The author wrote, “Many blind persons develop in the course of time a considerable ability to avoid obstacles by means of auditory cues received from sounds of their own making.” This included their own footsteps, or cane tapping, or finger snapping. He demonstrated that their ability to successfully echolocate was drastically reduced by distracting noises or earplugs.
As we saw earlier, the occipital lobe can be taken over by many tasks, not just those of hearing. Memorization, for example, can benefit from the extra cortical real estate. In one study, blind people were tested to see how well they could remember lists of words. Those with more of their occipital cortex taken over could score higher: they had more territory to devote to the memory task.33
The general story is straightforward: the more real estate, the better. This sometimes leads to counterintuitive results. Most people are born with three different types of photoreceptors for color vision, but some people are born with only two types, one type, or none, giving them diminished (or no) ability to discriminate among colors. However, color-blind people don’t have it all bad: they are better at distinguishing between shades of gray.34 Why? Because they have the same amount of visual cortex, but fewer color dimensions to worry about. Using the same amount of cortical territory available for a simpler task gives improved performance. Although the military excludes color-blind soldiers from certain jobs, they have come to realize that the color-blind can spot enemy camouflage better than people with normal color vision.
And although we’ve been using the visual system to introduce the critical points, cortical redeployment happens everywhere. When people lose hearing, previously “auditory” brain tissue comes to represent other senses.35 Thus, it won’t come as a surprise that deaf people have better peripheral visual attention, or that they can often see your accent: they can tell what part of the country you’re from, because they’re so good at lip-reading. Similarly, after an