The Thing with Feathers (21 page)

It may seem odd that we find it easier to absorb new information by
adding
to the load of data. Why is it more reliable to remember a number alongside Tiger Woods singing in a limousine than to simply recall the number on its own? Why do we have to construct elaborate stories merely to memorize the order of cards in a deck—which, by itself, is just fifty-two short entries? You’d think the additional layers of nonsense would require more gigabytes of storage space.

The brain-computer metaphor goes only so far, and in this case is misleading. Brains and hard drives accomplish some of the same memory functions, but they don’t operate the same way; though they both store information, they access memory differently. On a computer, a file is stored at a strict location—if you don’t know its address, you can’t find it. Brains seem to behave more like a search engine, using what’s known as content-addressable memory, meaning they bring up information by using subjects and keywords. Often, when searching for an obscure memory, the brain will find what it’s looking for only after another thought sets it off—that familiar eureka feeling of having something on the tip of your tongue when it pops up in an unrelated conversation.

This search-engine method is generally a good system for organizing vast stores of information. In one sense, the brain is one huge database of knowledge—but, again, the analogy doesn’t quite work. Various scientists have tried to estimate the capacity of their own brains in bytes, as if the brain were a computer’s hard drive, which becomes a vaguely circular exercise. According to one line of logic, the human brain has about 100 billion neurons, each of which might be able to store a
single piece of information, so one human brain could conceivably hold a couple terabytes of memory—about the same as a few of the latest laptops. Others point out that neurons aren’t isolated; if each one could connect with 1,000 other neurons, we’d actually have about 2.5 petabytes of storage—on the same order of magnitude as the total data processed by Google every day. Still others estimate that a brain might be able to store multiple exabytes (1 followed by eighteen zeros) of data, somewhere in the range of the combined capacity of all digital storage devices on earth today. These wildly varying numbers at least clearly illustrate our lack of understanding of the brain’s functions and the futility of comparing analog and digital, organic and robotic machines.

Still, there are a few intriguing similarities between the memories of computers and brains. Computers store information in a strictly defined hard drive, and brains also catalog long-term memories in one location, a region called the hippocampus. Many studies of memory have tried to relate hippocampus size with the ability to remember information, and there does seem to be a correlation. But again there are differences. While computer hard drives aren’t used for processing, the hippocampus is integrated with the rest of the brain and helps perform active functions. It is heavily involved in imagination, and it is the primary region used in spatial navigation. So we shouldn’t be surprised that, unlike a computer, we can remember images better than digits. Our hardware is set up to associate memories with vision and other senses.

Clark’s nutcrackers and self-professed mental athletes share a trait that computers don’t: While boasting uncanny memories, both birds and people primarily use spatial techniques to recall facts. Whether it’s pine seeds or playing cards, the brain—any brain—needs a story—any story—to latch on to important
information. Sometimes, a picture really is worth a thousand words.

Remember that spatial map that nutcrackers use to track down cached pine seeds? It’s a memory palace. Perhaps the ancient Greek poet Simonides should have looked to the birds for inspiration instead of a collapsing banquet hall. We struggle to believe that bird brains can remember where tens of thousands of seeds are stashed, but as it turns out, they use the same methods we do—which should give us hope for our own species.

We like to think the human brain is superior, but a recent experiment showed that birds are better at caching seeds than we are. A graduate student was pitted against a captive nutcracker, each burying dozens of pine seeds inside an aviary, then, after the passage of time, both digging up as many of their own caches as possible. The nutcracker beat the student by a large margin in a rare head-to-head cognitive win for birdkind. But in hindsight, it wasn’t really a fair contest. The canny nutcracker had had a lifetime of practice, and from its standpoint, caching seeds was a life-and-death proposition; it would starve if it ever forgot where its food was hidden in the wild. The graduate student had no such practice or motivation. Winners of memory championships believe that our brain responds to exercise like a muscle; if we can teach ourselves to memorize packs of cards in seconds, we could also learn to memorize thousands of food caches (assuming we wanted to bury our groceries around the yard). Perhaps if someone like Nelson Dellis went up against a nutcracker, the result would have been different. Not even computer scientists can quantify the limits of our own memory—the mind boggles itself on the subject.

The brain’s incredible mental capacity is granted with a clichéd caveat: Use it or lose it. In normal human brains, the
hippocampus shrinks by one or two percent per year in adults (up to about five percent a year in Alzheimer’s patients), and an idle hippocampus may shrink faster. In one fascinating study of chickadees, wild-caught birds lost a staggering 23 percent of their hippocampal volume just
five weeks
after being brought into captivity; caged birds, the scientists reckoned, had less necessity to navigate, interact, and remember information than their wild counterparts, so their brains shriveled (this measurement is known to fluctuate seasonally in the wild, too). But research has also indicated that this loss is negotiable, and that the brain may maintain itself better when regularly challenged. Use your head, in other words, or you’ll literally lose your head.

Although Simonides seemed to sense this truth, some of his ancient Greek acquaintances reportedly scoffed at his memory palace mnemonic technique. When the method was described to the Athenian politician Themistocles, he reputedly quipped: “I would rather a technique for forgetting, for I remember what I would rather not remember and cannot forget what I would rather forget.” More than 2,000 years later, scientists are still working on that one.

part three

SPIRIT

SELF-IMAGE

ART

ALTRUISM

LOVE

magpie in the mirror

REFLECTIONS ON AVIAN SELF-AWARENESS

W
hen a group of German researchers announced in 2008 they had discovered that captive Eurasian magpies can recognize themselves in a mirror, many scientists were surprised. Until then, only humans, the great apes, orcas, dolphins, and elephants—large mammals with big brains—had been shown to recognize their own images, despite a slew of experiments with mirrors and other animals, including many other types of birds. Yet this particular study showed unambiguous results. Three out of five individual magpies—Gerti, Goldie, Schatzi, Harvey, and Lilly—clearly recognized the bird in the mirror as themselves.

The mirror test, as it’s generally known, is straightforward: Stick an animal in front of a mirror and watch what happens. If it recognizes its reflection, it passes; if not, it fails. The tricky part is interpreting the results. There are two main problems: determining whether the animal really recognizes itself, and then figuring out what it means.

The German researchers knew this, and documented their study well enough to allay suspicion that the birds had really passed the test. They performed three different experiments with their five captive magpies. First, they introduced the birds to an open room with a dull gray plate leaning against one wall, and then replaced the plate with a mirror to see whether the magpies behaved differently in front of their reflection. Second, to gauge interest in the mirror, the researchers herded the magpies into an aviary with two connected compartments, one with the mirror and one with the nonreflective plate, and recorded how much time the birds preferred to spend in either
side. Finally, the researchers marked the five magpies with a spot of colorful dye on the chin that would be invisible to the birds except by using the mirror. If the birds scratched at the spot on their own chins while gazing into the mirror, they would show a basic understanding that their reflection wasn’t some other bird with something on its face. This type of “mark test” is the traditional cornerstone of mirror experiments with animals.

The first experiment clearly showed that the mirror affected the magpies’ behavior. At first, all five of the birds became visibly confused. They postured to their reflection as if it were another bird and searched behind the mirror for the perceived companion. The magpie named Harvey picked up several small objects in his beak and presented them to his reflection while flipping his wings as if in courtship, and continued to display aggressively in additional trials, as did Lilly. Gerti, Goldie, and Schatzi seemed to realize the deception more quickly and quit any kind of social behavior after one or two experiences in the mirrored room.

In the second experiment, Gerti, Goldie, and Schatzi explored the mirror at greater length, often slowly moving in front of it while intently watching their reflections, and spent most of their time in the mirrored compartment, showing intense interest, while Harvey and Lilly preferred to sit in the non-mirrored side. A rift was developing between the reactions of the first three magpies and the latter two.

The final mark test was most compelling. When a colorful mark was placed on their chins, Gerti, Goldie, and Schatzi each tried to claw at themselves when they saw their reflection. Gerti and Goldie continued to scratch at their chins in trial after trial, stopping only after the mark or mirror had been removed. The only explanation for their behavior was
self-recognition; when the birds were tested with a black mark that blended into their dark plumage, they appeared not to notice it, showing that they were indeed using the mirror. Gerti, Goldie, and Schatzi thus became the first three birds ever to pass the mirror test.

Because no bird had ever been shown to recognize itself in a mirror before, this experiment exceeded all expectations, with three out of five passing the test. The happy German researchers pointed out that chimpanzees, which have demonstrated the clearest evidence of visual self-awareness of any animal except humans, manage to pass the mirror test only about 75 percent of the time, even in the most productive studies. The magpie experiment wasn’t meant to cast sweeping judgments of avian intelligence—even if all five birds had passed, the sample size was too small to make generalizations—but rather to show a potential ability that hadn’t previously been recognized in birds at all. To that end, the study was wildly successful.

But it couldn’t answer the mirror test’s overall question: What does it mean, anyway? Ornithology had suddenly crossed into psychology and even philosophy. Ever since Descartes published his famous “Cogito ergo sum” revelation—“I think, therefore I am”—in the early 1600s, self-awareness has been a basic tenet of philosophy, and what some believe is an essential element of what it means to be human. Self-recognition may be the first step, but from there, the concept of self-awareness spirals into discussions of consciousness—an intuitive but slippery word that defies scientific definition despite centuries of debate. Although nobody claims that magpies are philosophers (or humans), the mirror experiment raised some new questions about avian intelligence and how it differs from our own. The implications of visual self-recognition in magpies aren’t altogether clear, but the ability to knowingly admire your image in
a looking glass must mark a kind of intelligence. Most animals can’t do it, and that makes magpies interesting.

At least, we
think
most animals can’t do it. Some scientists regard the mirror test as a flawed experiment, maintaining that it’s impossible to prove a negative result because we can never really know what animals are thinking. Short of asking directly, how could we ever tell for sure? Maybe animals just don’t care about mirrors enough to bother cooperating with our experiments. Because mirrors don’t offer many advantages in the wild, animals might think they’re boring and ignore them even if they know how they work.

And animals that have never seen a mirror might take time to get used to it, just as humans do. Children need repeated exposure to mirrors before they can comprehend the trickery of their own reflection—babies generally don’t figure it out until about age two—and even adults who have been blind their whole lives can be fooled by mirrors once their sight has been suddenly restored. Although we generally take our own reflections for granted, they require some practice, even for us.

Despite these criticisms, there does seem to be a worldly divide between those who can and can’t recognize their own reflection, and the German researchers showed that magpies belong in the first category, with us and just a couple of other higher animals. Interesting, indeed. But what does it mean? And why magpies?