It's a Jungle in There: How Competition and Cooperation in the Brain Shape the Mind (3 page)

It turns out, ironically, that the Pandemonium model as introduced by its developer was not quite as anarchic as it could have been. In the model, communication among components goes only one way—from bottom to top. We now know that among the levels of the brain, there is communication every which way—from bottom to top, from top to bottom, and so on. Across all the levels of the brain, neural ensembles communicate with each other directly or indirectly. Out of this seeming disorder come thought, perception,
action, and emotion. The brain’s unruliness is not an inconvenient truth to be rued. Rather, it’s what gives rise to the mind as we experience it.

If you allow for an unruly ruckus in your head, you don’t have to be undisciplined in your theorizing about what goes on there. You can speak of elves, imps, and demons for the fun of invoking these metaphorical beings, but all the while you can, and indeed must, appreciate that these entities are just functional mechanisms.

Functional mechanisms are required in a theory of the brain because mechanisms, in general, are needed to explain how things work. Also, and less trivially, brain mechanisms map onto the mental and behavioral functions they afford. Experience has aspects. Smelling is different from seeing, hearing is different from feeling, and so on. This basic fact of phenomenology (experience) suggests that the mind has distinct mechanisms corresponding to distinct qualities of experience.

A second reason to sanction the idea of distinct functional brain mechanisms (to which this book’s demons, elves, and gnomes correspond) is because the way we learn is, in general, gradual. No one learns to play a major piano concerto from day 1 at the piano. Piano students learn the elements of keyboarding first, gradually building up to more complex works. Even then, they study any given concerto one part at a time. Likewise for learning layouts of buildings or figuring out what it takes to satisfy your boss or your new
beau
or
bella
. If you agree that memories have different features, you need a way of explaining how those features are remembered. A useful way of doing so is to say that features are retained if their retention happens to heighten the chance for survival.

A third reason for assuming different functional mechanisms in the brain is that damage to the brain can result in selective deficits. A bop on the back of your head can make you blind. A blockage of blood to your left temporal lobe can make you aphasic (unable to use language). An injury to the front of your brain can leave you less feisty than you were before. Such selective deficits suggest that the brain has specific functional mechanisms.
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From the last statement, it’s important to stave off a possible misunderstanding. While it’s convenient to say that if there are mechanisms for
hearing
, for example, it’s important not to assume that those mechanisms reside only on “Eardrum Avenue.” Similarly, if there are mechanisms for
seeing
, it’s just as important to say that those mechanisms don’t live only on “Retina
Road.” Some aspects of experience may be traceable to particular regions of the brain—what I meant by Eardrum Avenue and Retina Road (fanciful names, in case you’re unsure)—but many aspects of experience are not. Understanding the meaning of a word, for example, is not traceable to just one place in the brain, at least as far as we know. Even if some place in the brain may appear to code a concept such as a famous actress, it can do so only by virtue of where it is physically situated in the brain and to which other parts of the brain it connects.
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Similarly, appreciating the beauty of a painting or feeling blue doesn’t have a single cranial locale, as far as we know. Many aspects of experience, or possibly
all
aspects of experience, reflect the goings-on of multiple brain regions acting as a population.

This remark is important apropos the appeal to little beings in the head. When I speak of those little beings, referring to them always metaphorically and never literally, I don’t mean to suggest that there is a one-to-one mapping between them and particular brain sites. The equation I am drawing instead is to functional mechanisms, which can be either widely distributed or locally represented in the brain.

I said above that many aspects of experience, or possibly all aspects of experience, reflect the goings-on of multiple brain regions acting as a
population
. I want to underscore that last word—
population
—because it is important for the thesis of this book.

When evolutionary biologists consider how species fare in the environment, they usually pursue population-level analyses. In fact, one of the most influential evolutionary biologists of the twentieth century, Ernst Mayr, made his most noteworthy contribution by exhorting evolutionary biologists to engage in “population thinking.” He argued that it makes more sense to think in terms of
groups
of organisms comprising a species than to think in terms of one individual at a time.
⁷
By his reckoning, one raccoon might be worth considering in connection with that animal’s going through your garbage, say, but to understand the place of any given raccoon in the larger ecosystem, it makes more sense to think about raccoons
en masse
, as a
population
. Population thinking, as Mayr called it, lets scientists make use of powerful quantitative tools like those employed in statistics to analyze the group as a whole. The population approach is useful not just in studies of evolutionary biology but also in studies of neural ensembles.
⁸

If it makes sense to speak of populations, why speak about individual mental fellows—those demons and elves to which I’ve referred? The reason is
didactic (for teaching). As I’ve already mentioned, this way of speaking about the brain can make the material fun and engaging, which is not to diminish the profundity of the questions to be addressed about the brain, nor to sidestep the often sad consequences of brain damage. In addition, and just to emphasize what I’ve already said, I don’t mean to ascribe full-bodied ambitions, hopes, or desires to the cranial creatures I’ll credit with undergirding cognition. On the contrary, I want to emphasize that every mental elf is totally dumb, doing just what it does with no awareness of how it fits into the larger scheme of things. No mental gnome has any more idea of the neural ecosystem of which it’s a part than does an amoeba in a lake or a fungus on a tree. But like conglomerates of amoebas or fungi, populations of neural demons have emergent properties, and that is where things get interesting.

How can those emergent properties arise from the collective actions of individual neural elves that, on their own, are clueless to their places in the neural ecosystem? Though the elves are ignorant of where or how they fit in, they’re not clueless about who their “friends” and who their “foes” are. With their friends they cooperate; with their foes they compete. The way they express cooperation, mechanistically, is through excitation, and the way they express competition, mechanistically, is through inhibition. If a neuron is friends with another neuron, it excites that other neuron. If a neuron is enemies with another neuron, it inhibits that other neuron. These two simple mechanisms—excitation and inhibition—allow for amity and animus, respectively, in the neural jungle.

One way that cooperation and competition are manifested is in levels of control. Much as there are dominance hierarchies in nature—pecking orders among poultry, for example—there are dominance hierarchies in the brain. The idea that neural ensembles dominate other neural ensembles is widespread in neuroscience. Oddly, though, there has been little discussion of how the levels of control come into being or why they exist. Thinking about these questions helps clarify the brain’s (and so the mind’s) dynamics.

Consider what it means to have dominant and less dominant mechanisms in the brain—to have “big guns” and “little pistols,” if you will. The bigger the guns, the fewer of them there can be. This may help explain why attention is limited, and why it exists at all. The defining feature of attention—a topic covered in
Chapter 4
—is selectivity, and the ultimate result of selectivity is being able to think of only one thing at once.
⁹
Your mind may flit back and forth from one idea to the next, but it’s impossible to have more than one thought at a time. If you’re thinking hard about this paragraph, for example, you can’t think equally intensively about what you’ll do on Saturday night. You might momentarily jump to that topic now that I’ve just mentioned it,
but for you to think as carefully about the topic of this paragraph as you did before, you have to return to it, leaving Saturday night to another time.

The fact that only one idea can be kept in mind suggests that some mental function is taken over by that idea. Whatever that mental function is, it’s the top spot in the mental milieu, the spot where competition is most intense.

Why should there be a top spot? To survive, mental creatures need helpful inputs. One way they can get helpful inputs is by affecting the output system that directs inputs back to them. If you’re a creature that survives by getting auditory input from the voice of the person you inhabit, then for you to survive it’s essential that that voice be heard. So if there is something you can do to increase the odds of that event, so much the better. Likewise, if you’re a creature that lives by the wafting of julep molecules into your owner’s nose, your chance of survival is better if he or she sniffs julep every so often. If something you do has the effect of getting your owner to sample that minty smell, your chances of survival can increase. You, being a dumb neural element, have no idea that what you’re doing may trigger julep sniffing, but if it does, you will be more likely to survive than if it doesn’t.
¹⁰

With many mental demons facing the constraint of needing input, there’s intense competition for access to the system that affects that input. The system that does this is, ultimately, the motor system, the system that moves muscles. To sniff you have to make movements that achieve sniffing, to speak (in order for you to hear your own voice) you need to move your mouth, and so on. There are only so many actions you can perform at once. You can’t move your hand forward and backward at the same time. You can’t speak and eat at the same time. Because you can do only a few things simultaneously, there is competition for the system controlling those actions. And those actions, in turn, affect what comes back into the nervous system, thereby affecting the survival chances of the creatures relying on those special inputs.

Turning to the headier realm of thought, I venture to say that if you can think of only one thing at a time, it’s because you can
do
only one thing at a time. Think of cars entering the Lincoln or Holland Tunnel on their way to Manhattan from New Jersey. The cars making their way to the toll collector funnel down. The closer the cars get to the entryway, the smaller the number of cars there can be.

Just as few cars can get very close to the toll collector or E-ZPass, very few thoughts can get close to consciousness at any one time—somewhere between 4 and 9 of them for most people.
¹¹
The smallness of the number of items that can be maintained reflects competition among cognitive candidates. To the
extent that few actions can be carried out at once, competition for access to the launch pad for action is likely to be intense.
¹²

Competition isn’t the whole story, however. Just as vehicles need to make way for other cars, trucks, and buses at portals to tunnels and bridges, neural systems must make way for other neural systems. There must be
cooperation
in the brain as well as
competition
. The cooperation needn’t be deliberate or explicit, as in signing a treaty or holding a door open for a follower.
¹³
Instead, it can be more implicit and may simply take the form of sending signals that tend to excite rather than inhibit other neurons or muscles. If exciting a neuron or muscle that tends to excite you tends to increase your chance of surviving, then, over time, it’s likely you’ll excite that neural system. You needn’t realize you are doing so and certainly don’t need an explicit plan to do so, but if the effect of your signaling other parts of the nervous system is, indirectly, to excite yourself, then that action is one you will perform repeatedly.

It is critical for the account developed here not to require that somewhere in the brain there is some single, most powerful, mental creature. There must be no chief executive officer, no awe-inspiring pooh-bah.
¹⁴
Why not?

Suppose you’re perched on the edge of a cliff and there, on the other side of the ravine, is another cliff you have to leap to in order to continue your journey. You feel yourself hesitating. “Should I really jump across that chasm?” “No,” you or some other part of you replies. Then you hear another voice in your head saying, “Go for it,” and then some other voice chimes in: “No, don’t!”

To whom do these voices belong? To you, of course, yet they seem to come from different individuals within you—a brave you, a cautious you, a you who triumphs, a you who trembles. It’s hard to tell which you is the real one. The chorus of voices makes you feel like you’re not one person but many. The truth is, you are many. You are a
population
.

Abandoning the idea that you’re a single self may be disconcerting. Can you decide anything if you’re not one person? The answer is that you can, because populations do so all the time. In elections, populations decide who will be mayor, governor, or president. In the market, populations decide things too. At the time of this writing, it was stylish for female students at my university to wear shorts that had the word “Pink” brandished in large letters across their behinds (not that I noticed, of course). A while ago, Penn State students proudly carried the word “Aeropostale” across their sweaters. Earlier, Tommy Hilfiger was the
nom de style
. Fashions are decided through collective
decision making. Neither Tommy Hilfiger, Amy Aeropostale (a name I made up), nor Paula Pink (another name I made up) issued edicts decreeing that everyone should wear their brands. The students decided collectively that those were the styles they’d favor.
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