Wayfinding
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What Simonides discovered through this experience was that by imprinting or stamping loci, or a place, in one’s mind and placing a memory in that place, it could be easily recalled. He recommended that one build an architectural structure with rooms and hallways imagined in great detail and then put information, names, and words in those places. When the orator or person needs to recall a piece of information, he revisits the building and the places where he has stored his memories. When it comes to long pieces of lyric poetry or ballads, the author of the Ad Herennium instructs students to learn the verses by heart by repeating them, and then replace the words with images and associate those images with loci.
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The method of loci was practiced by some of the great minds in Western history through the Renaissance, even after the invention of the printing press and ubiquity of the written word. Yates thought that these ancient memory systems were “at the great nerve centres of the European tradition” and that by the seventeenth century the art of memory was helping to midwife the age of scientific inquiry in Europe, helping scientists and naturalists to draw “particulars out of the mass of natural history, and ranging them in order.… Here the art of memory is being used for investigation of natural science, and its principles of order and arrangement are turning into something like classification.”
Some ancient Greeks it seems were wary of how the transformation from oral to literate culture might affect their memory capacity; they viewed the written word with apprehension. In the Phaedrus, Socrates recounts the story of the Egyptian god Theuth, who enthusiastically reveals the invention of letters to King Thamus, promising him that it will improve memory. But Thamus thought that he was mistaken.
For this invention will produce forgetfulness in the minds of those who learn to use it, because they will not practise their memory. Their trust in writing, produced by external characters which are not part of themselves, will discourage the use of their own memory within them. You have invented an elixir not of memory but of reminding; and you offer your pupils the appearance of wisdom, not true wisdom, for they will read many things without instruction and will therefore seem to know many things, when they are for the most part ignorant and hard to get along with, since they are not wise, but only appear wise.
Today the practice of rote memorization has been largely discarded in school curriculums, and we’re content to outsource memory to our phones or computers. But some people still use the method of loci. The majority of memory athletes, for instance. These are people who compete in the World Memory Championships and hold incredible records for memorizing the precise order of binary numbers presented over five minutes (over 1,000 digits total), or random words over fifteen minutes (300). In 2002, the Irish neuroscientist Eleanor Maguire decided to investigate why some people have better memories than others. She used neuroimaging sensors to watch which neural mechanics were at work when memory athletes memorized information. Ten individuals deemed “superior memorizers” were tested against a control group; none of them demonstrated exceptional intellectual ability. The only difference Maguire found was the part of the brain they used to recall information. The neuroimaging sensors found that while the right cerebellum was basically active in everyone tested, the memorizers also showed activity in the left medial superior parietal gyrus, bilateral retrosplenial cortex, and right posterior hippocampus—many of the brain regions implicated in spatial memory and navigation.
In order to memorize a series of numbers, then faces, and then photographs of detailed snowflakes, nine out of the ten superior memorizers had utilized a route strategy to recall the information. When the new items were presented, they placed them in a familiar loci and then recalled them by revisiting those places later. “The longevity and success of the method of loci in particular may point to a natural human proclivity to use spatial context—and its instantiation in the right hippocampus—as one of the most effective means to learn and recall information,” wrote Maguire and her coauthors in their study. As early as 1970, the Stanford psychologist Gordon Bower described the method of loci as a “journey” and a “mental walk” technique. The mnemonist creates a vivid mental place, akin to the brain’s spatial representation of an actual place, and navigates it during the quest for a specific memory. The method of loci takes a piece of abstract, disembodied information and gives it a spatial organization that transforms it into a memory supported by the hippocampus.
While Maguire didn’t find any structural brain differences between memory athletes who practiced the method of loci and a control group, she had previously found evidence that the hippocampus—the circuit in our brains responsible for building spatial representations used in navigation—is remarkably plastic. In 2000, she and a group of scientists at University College London published a study focused on the brains of London’s taxi drivers. To get a license to drive one of the city’s ubiquitous black cabs, drivers have to acquire what is called “The Knowledge,” which includes memorizing some twenty-five thousand streets and thousands of landmarks. Maguire wanted to know if these drivers would have more gray matter, the tissue containing synapses and a high density of neuronal cell bodies (the nucleus-containing center of the neuron), in their hippocampus as a result of this knowledge. The researchers used magnetic resonance imaging (MRI) scans and found that, amazingly, the answer was yes. London’s taxi drivers had significantly greater volume than a control group in their posterior hippocampus; it appeared that the number and complexity of navigational tasks a person practices influences the amount of gray matter.
Maybe, the researchers wondered, individuals with larger hippocampi were predisposed to become taxi drivers, a profession with a dependence on navigational skills. Yet their data showed that the amount of time spent in the profession correlated with greater volume, proving that the growth was accumulated. It was the environmental stimulus itself, the practice of navigation over time, that enabled plasticity, an ability to adapt and change, in this structure of the brain. Six years later, Maguire, Hugo Spiers, and Katherine Woollett published another study, comparing London’s bus drivers to taxi drivers. Both were navigating the same city, presumably dealt with the same levels of stress, and possessed similar levels of driving experience. The difference between them was that whereas the taxi drivers had to take novel routes that changed day to day depending on their passengers, the bus drivers followed fixed routes. By comparing the hippocampal matter in these two groups, the researchers hoped to conclusively understand whether driving itself was responsible for more hippocampal volume in taxi drivers, or spatial knowledge. Again, the taxi drivers were found to have greater gray matter volume.
The malleability of the hippocampus is arguably one of its most important features. Might an individual be able to influence through practice, environment, and skill their own cognitive potential? It seems so. The more time spent learning and practicing, the greater the gray matter, scientists have discovered, in the various parts of the brains of musicians, bilinguals, even jugglers. “The results from the present study continue to permit the view that learning, representing, and using a spatial representation of a highly complex and large-scale environment is a primary function of the hippocampus in humans,” the researchers reported, “such that this brain region might adapt structurally to accommodate its elaboration.”
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Before neuroscientists had discovered the role of the hippocampus—and its plastic qualities that could be harnessed for highly skilled navigation—the American aviator Harold Gatty argued unequivocally against the myth of a sixth sense, pointing instead to the seemingly limitless human capacity for learning. His book Nature Is Your Guide is a compendium of arcane and fascinating instructions about how people can learn to navigate without instruments. He wrote it in the late 1950s after an illustrious career teaching navigation on land and in the air, after he had retired to live in Fiji. (He died unexpectedly from a stroke just four months before it was published.) The book represents a lifetime
of knowledge accumulated by someone who loved adventure and seemed to be entranced with solving the puzzles of orientation and piloting using logic and his senses. Indeed, Gatty believed that in the process of “evolution of our civilisation,” people had lost what was once essential to our very survival: the power to observe nature.
Born in Tasmania, Gatty went to a naval academy at the age of fourteen and taught himself how to tell time by the stars while working on a steamship. He eventually opened a school of navigation in Los Angeles, teaching students how to read the sun and the stars. He invented a sextant to use in planes, and in 1931 he set a speed record by circumnavigating the globe in eight days. Gatty created Pan Am’s first transpacific air service route; Howard Hughes called him a “trail-blazing pioneer.”
Gatty’s book encompassed the globe, from deserts, mountains, and polar regions to oceans. His strategies for navigating these topographies drew on history and knowledge of Native Americans, Australian Aboriginals, Polynesians, Inuit, Europeans, and Saharan nomads. At every opportunity, Gatty emphasized that while those who grew up learning these skills will have “keener perceptions and more highly developed powers of observation than most of us,” anyone was capable of developing their memory, sense of time and distance, and observational skills with practice, in order to become what he called “natural navigators.” There was no special biological hardware at work in people who found their way without instruments. Their mastery was the result of tradition, a lifetime of exploration, and exhaustive knowledge of the landscape. If this was hard for his readers to grasp, Gatty said, that was because they had learned a conventional, Western version of history that taught them it was white explorers who had “discovered” native people in unexplored parts of the world. Gatty flipped that history: those same “natives,” he pointed out, had discovered their homes in much earlier and unaided feats of navigation.
Gatty believed technology itself had perpetuated a myth of biological difference between races. “[Scientists] build a wall of mystery, fable and myth around the natural navigations of the past. So used are we to navigating by the compass, the chronometer, the sextant, the radio, radar and echo sounder, that some of us just cannot believe that early peoples could make long journeys into unknown areas, and find their way through unexplored wilds and across uncharted seas with only their normal senses and traditional wisdom to guide them.”
These skills reminded Gatty of the Greek myth in which Ariadne gives Theseus a thread so he can find his way out of the maze of caves after slaying the Minotaur. In most places, said Gatty, the thread is an imaginary one. It is, just as Awa had described, a thread of memory.
WHY CHILDREN ARE AMNESIACS
The thread of memory that allows humans to explore without getting lost is one of humankind’s most fascinating cognitive powers. But there is a period when memory fails each of us. In infancy and early childhood we experience the world and formulate episodic memories—our recollection of events and autobiography—only to have them disappear and become unreachable to us in adulthood. Until I learned this, I was confused about why my early childhood memories were so fugitive until the age of six. Before that, there’s little I can grasp or distinguish as real versus imagined. After that, however, it’s as though my memory is ignited. I remember we moved to a rural New England town of just a few hundred people and rented a trailer at the end of a dirt road, nestled between a cow field and a long wooden chicken coop in which I could crawl and gather eggs. My mom planted a garden of herbs, flowers, and vegetables next to the coop and lugged a splintering telephone pole to its middle, putting an old green pie dish on top to make a bird bath. She canned fruit and cooked in a heavy iron skillet. After dropping me off at school in an exhaust-spewing Chinook camper truck, she taught autistic adults living at a nearby sheep farm how to weave on giant clacking looms and worked as a waitress. My dad, a housepainter, found work on the grander homes in the area or commuted to paint big Victorian houses. On the outside, our trailer was the quintessential redneck abode, but my parents were an odd amalgam; blue collar with serious spiritual aspirations, they counted their dimes to pay for pilgrimages to India and California.
What’s curious to me is that to this day I can draw a perfect map of this happy place. I know exactly where the grapevines grew along the granite-stone-lined ditch, the distance to the gnarled pear tree, the beehives, and every individual young pine tree on the perimeter of the cow pasture. I still know the curve of the stream and the exact place where it swelled to create a muddy bathing hole for me and thousands of tadpoles in the early summer, and its meandering path into a thicket and beyond to a beaver pond. I can draw each apple and peach tree, blackberry and raspberry patch, towering birch, and the dirt path through the trees to the giant field of goldenrod. I remember the placement of stones inside a bramble of old lilac bushes where no one else except for me could fit. There I camped out, secluded in my own private world, the first room of my own.
I would wager that if I gave you this map and transported you back in time, its to-scale detail would allow you to navigate this place accurately. And remarkably, my memory extends beyond our home to the entire town. Why did my mind have such a frustrating void of my early years and the sudden lucidity and exactitude of my spatial memory after the age of six? For a while I chalked it up to some sort of trauma simply because the four years we lived in the trailer were the most stable of my then-young life and, it would turn out, the last secure moments of my adolescence. We left it for a period of repeated displacement and then divorce; from the age of ten until I was twenty-eight I would never live in the same place for more than a year or two. Did this period of stability explain the resolution in which my mind could recall our ramshackle Eden? Did I remember it so well simply because I had been happy? And why, I wondered, did my memory of these years so often take the form of a map that included the myriad routes and places where I had explored and run riot?
It was a neuroscientist who first told me about the universal phenomenon of amnesia in children. Kate Jeffery is an English neuroscientist whose laboratory at University College London studies the behavior of hippocampal cells in rats. At the core of her interest is the mystery of why the human brain seems to use the same neural circuit for navigating space and episodic memory; she has called it one of the most outstanding questions about the brain. “Why would nature have used the same structures for both space and memory, which seem so very different?” she wrote in Current Biology. “An intriguing possibility is that the cognitive map provides, in a manner of speaking, the stage upon which the drama of recollected life events is played out. By this account, it serves as the ‘mind’s eye’ not only for remembering spaces, but also the events that happened there and even—according to recent human neuroimaging evidence—imagination.”
I met Jeffery at a conference in London and asked her about my own experiences with childhood memory. Was there an age at which our cognitive powers for spatial mapping are “turned on,” so to speak? How the spatial system develops in infancy, Jeffery told me, is still very much an open-ended question; we don’t know how much of our brains are hardwired or how much spatial experience is necessary in order to condition the functions of the brain. Some studies have shown that animals raised in featureless or small confinements struggle with simple spatial tasks, but how this translates to humans is unclear. “I think the field is still grappling with these issues. We’re not exactly sure. But there is a phenomenon, this period of time in infancy and beyond during which we don’t have lasting episodic memories, we don’t seem to be laying down those memories,” she said. And, Jeffery pointed out, young infants don’t form cognitive maps in the way adults do. “Their spatial organization of information is a lot less rich,” said Jeffery. “It’s possible that memories you form as an infant, because the hippocampus is still developing, may get overwritten or disturbed by the new circuitry that is still developing. And as an adult, you can’t retrieve those early life memories the way you can later ones.�
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The hippocampus of rats is anatomically similar to humans, and for Jeffery, looking into their brains and listening to the activity of their neurons firing as they move provides tantalizing glimpses into the physiology of spatial mapping and memory. As we sat together talking about these questions, I asked Jeffery if she could explain the process by which neuroscientists think the hippocampus perceives and creates representations of space. Jeffery graciously took a piece of paper and pencil and began sketching a series of boxes and arrows, building a classic circuit diagram to illustrate the neural components of the hippocampus. She started with a box representing the entorhinal cortex, labeled it “EC,” and split it into five layers representing various cell types. The entorhinal cortex, she told me, is the main interface between the neocortex, the part of the human brain associated with higher intelligence, and the hippocampus. All of the primary sensory areas—vision, olfaction, audition, touch, what Jeffery described as “a little bit of this, a little bit of that”—feed into the entorhinal cortex. From that box she began drawing arrows to other boxes labeled “DG,” “CA3,” “CA2,” “CA1,” and “SUB.” These were the main components of the hippocampal circuit, each one fed by the various layers of the entorhinal cortex. “By the time you get to the hippocampus, quite a lot of stuff has happened, these senses are very highly processed,” she explained. “But it turns out that layer two goes to CA3, layer three goes to CA1 and the subiculum, but there is an output from CA1 that goes back into layer five of the entorhinal cortex.” She paused, looked at my furrowed brow, and chuckled. “So it’s sort of like that but there’s lots of backwards and forwards.”