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Authors: Shimon Edelman

The Happiness of Pursuit: What Neuroscience Can Teach Us About the Good Life (13 page)

BOOK: The Happiness of Pursuit: What Neuroscience Can Teach Us About the Good Life
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The varieties of episodic memory maintained by a species depend on its habitat. For a desert bighorn, this has always meant just a patch of territory. We humans started that way too, but have by now assimilated into this category various spaces that are not entirely, or even not at all, spatial. Instead, these spaces are abstract, like the possibility space. In such a space, one can still meaningfully discuss proximity (which translates into similarity between abstract objects, such as two action plans). Even for us, however, the roots of abstract representations are firmly planted in the basic functional need to explore and make sense of the wild environment into which we are born, armed only with the knowledge of how to learn and a notion that every thing has its place.
For human babies, forays into the wild begin in the playroom or in the backyard as they crawl about and explore the little world centered on the place where they are released by a caregiver. Among the kinds of regularities that babies need to discern in the maelstrom of sensory information that spins around them are names for things—certain sound or gesture combinations that go with certain objects or actions. Sometimes objects do receive explicit labels; only inconsiderate or stoned parents would ever exclaim, “Look at the bunny!” while pointing at something other than an actual bunny (live or stuffed). More often than not, however, the baby has only circumstantial evidence to go by, as when an object gets both mentioned and shown, but not at the same time.
Experimental studies show that in such cases babies learn more reliably if the naming of an object and its appearance are made to share the same physical location—for instance, by offering the baby a verbal label for a novel object while snapping fingers in the place where it had appeared earlier. In using space in this manner, human babies very likely rely on the same brain circuits and mechanisms that support location-bound episodic memory in other mammals (all of which have a hippocampus). It is because of this sharing of dedicated computational resources between episodic memory and language-related tasks that drivers are more likely to get lost if they are made to navigate a not entirely familiar city while maintaining a conversation.
13
A Moveable Feast
 
Not only mammals qualify for an episodic memory system: chickadees, nutcrackers, jays, and titmice have it too. These and many other species of birds depend for their survival on caching food items, such as seeds or dead worms, that they later retrieve. The number of caches typically runs in the thousands, underscoring the large memory capacity that is needed to support this behavior. Carefully controlled studies have revealed that this memory is episodic: rather than relying exclusively on common characteristics of a cache location, birds memorize the actual locations they visit. They also remember the type of the food item that they store in each location: scrub jays, for instance, return to caches of perishable wax worms before revisiting places where they have stored pine nuts, which do not spoil.
14
Because of the usual selection pressure, the ability to memorize past episodes is indulged by evolution only insofar as it carries future dividends. The scrub jay’s obvious future payoff from remembering where it cached a wax worm is a tasty snack at a later time, but there is also a less obvious and much more interesting side to episodic memory, avian or human: it can support time-travel, of a kind that is perfectly compatible with the laws of physics and fully paid for by the evolutionary benefits it confers.
It is easy to see how a mind that is equipped with episodic memory has what it takes to travel mentally into the past: it can do so by recalling the circumstances of previously experienced episodes and re-creating them in the represented present, within the workspace of the mind’s war room. With only a slight modification, the very same set of cognitive tools can also support mental travel into the future: one needs merely to modify certain aspects of the represented situation to turn retrospection into prospection.
15
The study that demonstrated this ability in scrub jays took advantage of their gourmand predisposition. Jays prefer not to eat the same food day in and day out if they can help it. To motivate them to think about a future meal, experimenters taught the birds, over the course of a few days, that in one of two locations they would find a breakfast of peanuts and in the other— kibble. When given a choice of food to store on the eve of the test day, the jays cached kibble in the peanuts-for-breakfast location and vice versa, thus demonstrating not only a love of dietary variety but also an ability to indulge it by anticipating and acting upon a future need rather than an immediate urge.
16
In this task, the key aspect of the represented breakfast location that the bird’s brain needs to modify to switch between the present and the future is its food label. In the “present” setting, the food cue is simply what the perceptual system tells the rest of the brain it is. In contrast, in the “future” setting it is what the bird expects, or would like it to be, given its earlier experience with the location. It is easy to envisage how switching between these two settings can be accomplished by neuronal circuits in which “place cells” act in tandem with neurons that represent various food concepts.
Systems based on episodic memory explore the future by reimagining the past, just as in way-finding they plan future moves by consulting past peripatetics. In the rat brain, episodic place-specific cells, whose response properties are shaped by the animal’s situated experience, can also fire prospectively as the rat ponders the choice that would bring it to the location in question. The circuits that encode episodic information and thereby allow rats to weigh future options are consolidated during sleep as the animals dream about the places they visited during the day and rehearse their actions.
This is very likely the same neural system that helps humans navigate, not just through “space” space, but also through what I called earlier the possibility space, in which sequences of complex actions are learned, planned, and executed (as demonstrated with such flair by Chico Marx’s anticipation of Groucho’s every move in front of the nonexistent mirror). But does exploration of possibility spaces really count as mental time-travel? One could argue that planning for the future may in principle proceed “functionally,” by taking estimated future needs into account, without ever leaving the experienced—or, to use a philosophical term,
phenomenal
—present.
What distinguishes a truly experiential, phenomenally prospective state from one that pertains to the future only functionally is spatial grounding. A first-person perspective—the feeling of being right here, right now—is a key component of everyday phenomenal experience (about which I’ll have more to say in Chapter 6). This feeling is easy to manipulate, as the following two little experiments will demonstrate. (Don’t attempt them if instead of reading this book you are listening to it while driving.)
First, think of your fridge; now open it mentally and tell me whether there is any milk left. Is there? If despite my warning you did try this experiment while driving, and if you are still in one piece, slow down and listen to any noises originating from underneath your car: while mentally sticking your head inside your fridge, you may have run over something that you should have braked for.
Now, imagine that a freak storm has buried your neighborhood under deep snow and think of opening your fridge in two days’ time. Is there any milk left now? Your answer is likely to differ from the previous one, because things have changed: the kitchen looks strangely bright because of all the snow outside, and the milk carton feels much lighter. This stands to reason: you are in the same imagined place now as before, but at a different imagined time.
These exercises (easy, fun, and safe, if you followed the instructions) illustrate the phenomenal realism of mentally shifting the first-person perspective from here and now to there and then. This makes mental space-time travel real in the most important relevant sense: for the experiencer, who necessarily always has the last word in matters pertaining to his or her or its own experience, it
feels
real enough.
17
Because your space-time machine is inside you, rather than the other way around, it works only for you. Only you can use it, and then only to travel to your own (imagined) past or future, or, if you fix the time dial and spin the space dial, your own (imagined) geography. Because there must be a “there” and a “then” for you to go to before you can leave the here and now, the more you have been around (in time and space), the richer the virtual universe that you can explore. Most importantly, because this exploration in turn enriches your cognitive arsenal, making you better fit to face the
real
real world, it is viewed favorably by evolution.
The evolutionary angle helps us understand not only why mental space-time travel comes to us so easily, but also why we indulge in it at every opportunity—to the extent that special training in awareness meditation is needed to overcome the virtual wanderlust.
18
Episodic memory mechanisms make it possible for the hedonic value of a happy experience to transcend the boundaries of real time and space. This is why reminiscing about past happy experiences or anticipating future ones may feel good—under the right circumstances.
As Dante notes in
The Divine Comedy
, “There is no greater sorrow / than to be mindful of the happy time / In misery.”
19
By the same account, however, happiness is brought into sharper focus when experienced against a dark background. In Book XV of
The Odyssey
, the old man of Ithaca who tends pigs for the household of its long-absent king befriends a beggar, newly arrived on the island after much ill luck and hardship. Having heard his complaint, the wise swineherd encourages the beggar to enjoy the offered food, wine, and shelter, because, he says, “In later days a man / can find a charm in old adversity, / exile and pain.”
20
The swineherd does not recognize in the beggar Ulysses, who has secretly arrived back in Ithaca after twenty years of war and peregrinations. The genre of the novel having not yet been invented, Homer does not tell us what it was that Ulysses felt during his long exile, but it seems safe to assume that what kept him going was the promise of happiness—the anticipation of the much-hoped-for return home.
Following the sensibilities of the age, the story does not suffer Ulysses to return home empty-handed. The fabled Phaiakians, who ferry him overnight from their island to Ithaca and set him, still sleeping, on the shore, leave him many gifts: cloaks and tunics, cauldrons and tripods, bronze swords and golden wine-cups, and (somewhat improbably) bars of gold. Everything that we hear about Ulysses tells us, however, that apparel, accessories, and even gold have no dominion over him. Ajax, having lost the debate over the Shield of Achilles, goes mad with thwarted greed and kills himself; Ulysses, having won it, happily gives it up.
Recent empirical studies of the comparative hedonic value of various kinds of experience suggest that Ulysses was wise in treating material possessions lightly. The enjoyment of material purchases tends to fade with time: the kick you get out of becoming the owner of a new cooking cauldron is soon gone, even if satisfaction from its use persists. In comparison, experiential purchases leave a trace of happy episodic memories that can be relived: go sailing around the Mediterranean and you’ll appreciate the thrills of that experience for the rest of your life, even if it takes you a decade to get back home.
21
As Ulysses arrives at long last in Ithaca, he is fabulously rich, and not because of the Phaiakian fortune. Among his real treasures are his memories of the victory at Troy and of the long and circuitous journey home. Listen to Constantine Peter Cavafy, the melancholy Greek poet of exile:
Keep Ithaka always in your mind.
Arriving there is what you are destined for.
But do not hurry the journey at all.
Better if it lasts for years,
so you are old by the time you reach the island,
wealthy with all you have gained on the way,
not expecting Ithaka to make you rich .
22
 
It is all good, down to the last line, where, it seems to me, Cavafy, who lived and died alone in distant Alexandria, speaks out of bitterness. Ithaca does make Ulysses rich, with the priceless treasures of home: the sound of the surf in its coves, the texture of its stones under his sandals; the smell of its wild thyme; the sight of its olive trees and vines; the taste of their fruit; and also: the approval and admiration of his father, Laërtes; the valor and presence of mind of his son, Telemakhos; and the companionship and love of his spouse, Penelope.
 
SYNOPSIS
 
Not just cognition but life itself, which depends on biochemical information processing, would be impossible were it not for the world’s predictability. Yet, the patterns formed by many types of events that matter to a mind that is trying to fend for itself, such as competition among individuals and species, shift over time. Because of that, and because of how difficult it is to squeeze specific helpful hints about how the world works through the informational bottleneck of the genome, evolution’s best bet is on minds that can learn through experience and thereby both attune themselves to environmental regularities and deal with environmental change.
What kind of computation does it take? To discern regularities that can be relied upon in planning future behavior, the brain must keep track of past events and the sequences they form and distill from them trends that can be projected into the future. This insight reveals the true computational task of a faculty of the mind that is familiar to all of us as memory. Far from being a mere repository for odd pieces of information, your memory is charged with relating the episodes of your life to each other, seeking recurring patterns—crisscrossing paths that run through the space of possible perceptions, motivations, and actions.
Because of its likely evolutionary roots in way-finding, episodic memory relies heavily on taking note of locations in which events happen and of their spatial relationship, turning a representation of the layout of the physical environment into a foundation for the abstract space of patterns and possibilities that it constructs over the mind’s lifetime. As they fall into place the paths through the possibility space can support mental travel in space and time, which are both simulated to the best of the mind’s knowledge and ability. Episodic memory is thus the mind’s personal space-time machine—a perfect vehicle for scouting for and harvesting happiness.
 
BOOK: The Happiness of Pursuit: What Neuroscience Can Teach Us About the Good Life
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