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  As we explore the details of these different means of wayfinding, we will gradually mark out the boundary that separates human abilities to deal with problems of space from those of other animals. Some animals rely on special senses, such as magnetic field sensitivity or the ability to analyze special properties of light waves that we cannot see. Other animals possess prodigious talents for memorizing their paths or the appearance of thousands of subtle landmarks in a seemingly featureless expanse of forest or meadow. Human beings follow a somewhat different course. Though some of us, particularly ancient wayfinders in preliterate societies, have been able to train ourselves to be sensitive to subtle perceptual cues about locations and routes, we more commonly find our way by connecting different types of images of places with stories that link one image to another. This kind of navigation can sometimes get us effectively from one place to another, but we sacrifice much of our understanding of how places are connected, the geometry of the world, in favor of a simpler view of the spaces we inhabit as a series of connected nodes. We can learn what is connected, but our command of the hows and wheres of such connections is shaky at best.

  In the second part of the book, we will explore the implications of the differences between human beings and other animals for problems that involve our understanding of where we are. How do the sizes and shapes of our dwellings, offices, factories, civic buildings, and cities reflect our abilities (or inabilities) to come to terms with physical space? How does our unique conception of space as a topology of connected nodes influence the way that we interact with colleagues at work? How has modern technology, especially instantaneous communication using everything from the telephone to the Internet, changed our understanding and use of physical space? Has the fact that our minds are fuzzy about the geometry of the everyday world accelerated the extent to which such technologies have penetrated our lives? Would an animal that understood in its bones the meaning of space have been able to adapt to the hyperspace of the World Wide Web and virtual environments spanning the globe?

  RECAPTURING PLACE BY RETHINKING SPACE

  There can be little doubt that our ability to stand outside of real space and look back into it, reflect upon it, and shape it to our own designs and purposes has been responsible for much of the form of modern life. We have used technology to adapt the world to our purposes, and our own ability to adapt to technology is made possible by the way our brains perceive space. At the same time, our ability to step outside of the world’s geometry mentally has resulted in a sad kind of detachment between us and the rest of the planet. This state of detachment may contain some important clues about another of the great paradoxes of human nature: how can a being whose mind is capable of such dramatic acts of understanding and creation wreak such havoc on its own home that its very future stands in some doubt? Perhaps the more pressing question is whether understanding where mental space comes from and what is done with it can help us to find solutions to such vexing problems. Can we rethink our relationship with space to make us more aware of the effects of our actions on the state of the planet? Can the artful design of buildings and cities encourage us to make connections to our spaces and places that will help us to take more responsibility for them? Could the secret to recapturing our sense of environmental stewardship reside in recapturing some of the connections with the planet that were possessed by ancient human forebears whose lives depended at every moment on their understanding of where they were? Can we co-opt some of the same technology that has helped us to conquer space in our personal lives to make us more aware of the wider sweep of space that is beyond the purview of our senses?

  I hope you will find this book an optimistic one. It would be sad to think that a species that can produce Einstein, Mozart, Mother Teresa, and Shakespeare could short-circuit its own future, and the future of its home planet, because of a curious cerebral glitch that has simultaneously allowed us to conquer the wide spaces of the solar system but to become lost in a shopping mall. It seems more important than ever that we recognize that the most important impediments to our survival and flourishing are not technological barriers but psychological ones. More than anything else, moving forward in time and space will require that we understand not just who we are but where we are.

  PART I

  WHY ANTS DON’T GET LOST

  AT THE MALL

  HOW HUMANS AND ANIMALS NAVIGATE SPACE

  CHAPTER 1

  LOOKING FOR TARGETS

  SIMPLE TACTICS FOR FINDING OUR WAY

  THAT WE SHARE WITH ALL OTHER ANIMALS

  Following the light of the sun, we left the Old World.

  CHRISTOPHER COLUMBUS

  We’ve all done it. At a meeting, a conference, a wedding, or a simple potluck gathering with friends, the food appears. Though manners may prompt us to restrain ourselves for a few minutes, our antennae wave, our restless feet shuffle, and we make a beeline for the tables. If a scientist were to hover above us and measure our movements, it would be easy to show the average guest-to-plate distance as a steadily decreasing mathematical function. This class of behavior, called taxis, is the simplest kind of spatial behavior that can be imagined. All that is required is a target (that magnificent roast of beef), a sensor or two (our well-tuned nostrils and eyes), and some kind of motive force (sore feet squeezed into formal shoes will do nicely).

  Life does not always treat us so kindly, though. On our way to the table, Longtalker Larry makes a perfect intercept course. How to rearrange the missile trajectory so as to home in on the canapés while avoiding verbal entanglement with Larry? The buffet table has two rows of food. On the closest side is Aunt Betty’s famous potato salad, but it looks a little bland. The better bet is Sarah’s Spicy Potatoes, but they’re just out of reach. We’ll need to thread our way through a crowd, momentarily losing sight of the target completely, in order to plan the return foray to starch Valhalla on the distal side of the room. What’s the quickest way? Perhaps the party is in a building we’ve never seen before. The sweet aromas are everywhere, but compared to what vision gives us, they don’t make much of a spatial cue. Which way do we go first? How do we conduct an efficient search?

  Compared with many of the stories of feats of navigation that I will relate to you, finding your way to and then around a table full of food is small potatoes (Sarah’s if you’re lucky). Nevertheless, all such behaviors, ranging from the trivially simple taxis to the complex wayfinding task, point to one basic truth of biology. Unlike the potted geranium sitting in my window, you and I, like all other animate beings, need to be able to move from one place to another to survive. In order to remain nourished, I must get up from my chair and go to the fridge to find food. In order to avoid a premature demise, I need to leap out of the way of the bus that hurtles down the road toward me. The whole raw biological point of my individual survival is to reproduce. But this, too, requires movement. In order to pass my genes on, I need to be able to get up and walk around until I find a mate. (This, you may argue, is something of an oversimplification.) To survive, we must come to terms with space and time. Whatever the physicists and philosophers might say about these things, movement is defined as a change in place over some duration of time. Given this, it is not at all surprising that nature has produced a wide array of mechanical devices that produce movement (legs, wings, fins, and so on). In addition, we have evolved an even more impressive arsenal of tools that allow us to know where to move—that is, to find our way through space to important goals such as sustenance, warmth, safety, and sex.

  The simplest tricks of navigation are perhaps so obvious that we don’t even think of them as being tricks. You are walking down the aisle in a grocery store when, just ahead of you, you see the box of spaghetti you’ve been seeking. With little or no conscious effort, the box is soon in your hand and then in your shopping cart. What’s to explain? This seemingly trivial piece of behavior—moving to a clearly visible target—is something that we do hundreds of times a day. Such behaviors are required
of all animals that move, yet they are accomplished in a wide variety of ways.

  The most primitive kinds of animals, one-celled creatures such as bacteria, though their needs may be simple, must still possess a basic toolkit that allows them to find their way to conditions that sustain life: light, heat, and sustenance. Sometimes these unicellular denizens of our soil, water, and even our own bodies can employ a search strategy much like a child playing a game of blind man’s bluff. Their rates of movement rise and fall with the activity of sensors tuned to the concentrations of heat, light, or chemicals that surround them, and these changes in movement bring them inexorably into contact with their goal. Other than the movement of a plant bending toward the light, it is difficult to imagine a simpler mechanism by which a living thing can deal with the problems of space.

  In other cases, such tiny creatures as these may possess specialized equipment to help them guide their movements. In 1996, a group of scientists, headed by Dr. David McKay of NASA’s Johnson Space Center, claimed they had discovered fossil evidence for the existence of life on Mars in a lump of meteoric rock that had been collected from the Antarctic.1 Analysis of the chemical composition of the rock left little doubt that it was of Martian origin, and the peculiar formations inside the rock looked suspiciously biological. Researchers thought they could see tiny cell bodies, reminiscent of our own earthly bacteria.

  As some of McKay’s early evidence has been disputed by others,2 the initial excitement has died down, but he remains convinced that the particles of magnetite that were found in the sample once constituted a part of a Martian life form. Magnetite is found in various places on our planet, but one of the most interesting homes for this magnetic mineral is inside single-celled organisms that employ a unique style of navigation. So-called magnetotaxic animals use particles of magnetite as tiny compasses that orient their bodies with planetary geography. Though these magnetite bodies take advantage of the earth’s magnetic field in exactly the same way that makes the Boy Scout compass face north, in this case it is not to help them to read maps correctly but to do something much simpler: the magnetite pulls these tiny aquatic animals downward into the lakebeds lining their watery homes, where they find food, safety, and comfortable temperatures. The origin of the magnetite found in McKay’s samples is a matter that still swirls in controversy, but if he is correct, not only will his discovery constitute the first evidence of extraterrestrial life but his claim will be based on an elementary form of navigation.

  The rudimentary navigational tools that I have described are based on a mechanism that allows an animal to drift up or down a gradient of light, heat, magnetism, or the concentration of some chemical. Such mechanisms can serve a variety of functions where animals need to get from where they are to an easily defined target such as a strong source of light or a warm pool of water. Simple as they are, some things are still not well understood about these elementary mechanisms. Indeed, some of the fine details of bacterial navigation have led researchers to suggest that these tiny beings possess a type of cognition not different in kind from that found in much larger multicellular animals.

  When a hungry urban primate tries to zero in on Sarah’s Spicy Potatoes in the buffet line, this is yet another form of taxis, but for reasons that will soon be clear, the technical hurdles that must be overcome to reach such targets are considerably more complicated than those faced by the average amoeba or slime mold.

  THE POWER OF TWO

  A frog sits motionless at the edge of a muddy stream, seemingly oblivious to the passage of time and the flow of events. When a fly happens within striking range, the frog’s tongue lashes out to capture it with such speed and precision that the fly seems to have vanished into thin air. Clever scientific experiments using time-lapse photography have shown that the frog can not only discern the direction of the fly’s movement but also assess the fly’s distance with enough precision to ensure accurate contact between sticky tongue tip and hapless fly torso.3

  Though prey catching in frogs might seem very different from taxic behavior in bacteria, what they share is that they are simple behaviors designed to help an animal make a connection with a spatial target. One advantage that an animal like a frog has over a microscopic one-celled critter is simply that of size. With a big enough body, sensors can be placed in such a way that they can be used to triangulate on the location of a target. A pair of sensors—the eyes in this case—can make precise estimates of the locations of target objects without having to engage in the complicated trial-and-error methods used by much smaller animals.

  Bilateral symmetry (that is, a body composed of two more or less identical halves) is common in nature, and with such symmetry comes paired sense organs. The mechanism by which pairs of sensors can produce useful orienting behaviors can be exceedingly simple. A basement hobbyist can easily construct a small machine capable of such seeking behaviors using nothing more than a pair of sensors (for example, simple light detectors that can be purchased for a few pennies at an electronics shop), a pair of wheels, and a powered motor. By wiring the machine together in such a way that each sensor is attached to a wheel on the opposite side of the body, the machine can be made to roll rapidly toward sources of light. Alternatively, reversing the wiring will produce a timid machine that seeks out dark corners.4

  More sophisticated uses of paired sensors involve comparing the images that are presented to each sensor to arrive at an estimate of the location and distance of a target. When we look at an object, its image falls in slightly different locations in each of our two eyes, and our brain can compute the distance of the object based on such differences. When we listen to a sound, the differences in the qualities of sounds arriving at our two ears can be used in similar fashion to compute the location of the sound source. The power of two in this case means that animals possessing paired sensors do not need to engage in hit-and-miss games of blind man’s bluff in order to get close to the things they need. Instead, comparing the messages conveyed by each of the two sensors provides a rapid and accurate estimate of the location of a target. In simple machines built with light detectors and wheels, or in frogs and toads sitting stoically waiting for dinner to come within tongue’s reach, the use of paired sensors is a considerable advance over the simple taxic mechanisms of bacteria. In more sophisticated animals like us, many more layers of neural machinery are involved in regulating our movements with respect to targets of interest. As preponderantly visual beasts, the story begins with our eyes.

  Spend a minute or two observing how your own eye movements contribute to your perception of the world. Find a point somewhere in the room and try hard to maintain your gaze on that location. While doing this, notice how much you can see of objects just outside your fixation point. If you hold your gaze steady, you’ll notice that your perception of the rest of your setting consists of nothing more than a few blobs of varying brightness. Notice how little can been seen clearly when the eyes are held in a stationary position. Visual details are available in a small region of space around your fixation point, but nowhere else. To build an integrated view of the layout of the space we occupy, we need to move our eyes ceaselessly.

  Working in the 1960s, when the technology for studying eye movements was primitive compared to the tools that are available to us today, Alfred Yarbus, a pioneer in the scientific study of eye movements, had participants in his experiments wear small mirrors that were attached to their eyeballs by means of small suction cups. (Yes, it was unpleasant. And, yes, Yarbus participated in his own experiments.)5 In some experiments, participants were asked to examine paintings while Yarbus recorded the patterns of their eye movements. When the eye-movement recordings were superimposed on the paintings so that it was possible to see what the participants had been looking at, Yarbus discovered that eye movements were not scattered randomly across the paintings; nor did they seem to carry out any kind of systematic search (such as from top to bottom or from left to right, as one might imagine a machine would do). Instea
d, the eyes tended to seek out the parts of the picture that were most salient. For example, an inordinate amount of attention was paid to the eyes of the human figures in a painting. Yarbus was able to show that the pattern of eye movements seen during the viewing of a painting depended on the context of the viewing. If he asked people to answer questions about what they were seeing, their eye movements would reflect the strategies that they were using to search for answers. Our eye movements are not driven by what is biggest, brightest, or flashiest in a visual scene. They reflect the purpose of our looking.

  Though Yarbus’s clever experiments stimulated legions of future researchers to use measurements of eye movements as a kind of window into our minds, he was limited by the crude technology of his day. Participants were required to have their heads restrained for periods as long as three minutes while viewing his pictures, and the little stalks that were attached to their eyeballs were uncomfortable and distracting. Today, it is possible to measure eye movements with great accuracy using a much less invasive method. Participants in such experiments can simply wear a pair of glasses that contains miniature cameras to record the movements of their eyes. Using this method, much has been learned about how our eyes capture critical information.