It's a Jungle in There: How Competition and Cooperation in the Brain Shape the Mind Read Online Free Page A

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 theextent 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.
No Chief Executive
    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,