§4-9. A-Brains and B-Brains
---Socrates: Imagine men living in an underground den, which has a mouth open towards the light—but the men have been chained from their childhood so that they never can turn their heads around and can only look toward the back of the cave. Far behind them, outside the cave, a fire is blazing, and between the fire and the prisoners there is a low wall built along the way, like the screen, which puppeteers have in front of them, over which they show the puppets.
---Glaucon: I see.
---Socrates: And do you see men passing along the wall carrying all sorts of vessels, and statues and figures of animals made of wood, stone, and various materials, which appear over the wall? Some of them are talking, others silent.
---Glaucon: You have shown me a strange image …
---Socrates: Like us, they see nothing but only the shadows of themselves and of those other objects, which the fire throws on the opposite wall of the cave… Then in every way such prisoners would deem reality to be nothing else than those shadows...
Can you think about what you are thinking right now? Well, in a literal sense, that’s impossible—that each such thought would change what you’re thinking now. However, you can settle for something slightly less—if you imagine that your brain (or mind) is composed of two principal parts: Let’s call these your A-brain and B-Brain.
Now suppose that your A-Brain gets signals that stream from such organs as eyes, ears, nose, and skin; then it can use those signals to discern some events that occur in the external world—and then it can react to these, by sending signals that make your muscles move—which in turn can affect the state of the world. By itself, it’s a separate animal.
However, your B-Brain has no such external sensors, but only gets signals that come from A. So B cannot ‘see’ any actual things; it can only see A’s descriptions of them. Like a prisoner in Plato’s cave, who sees only shadows on that wall, the B-brain mistakes A’s descriptions for real things, not knowing what they might actually mean. What the B-Brain sees as its ‘outer world’ are only events in the A-brain itself.
Neurologist: And that also applies to you and me. For, whatever you think you touch or see, the higher levels of your brain never can actually contact these—but can only interpret the representations of them that your other resources construct for you.
When the fingertips of two ardent lovers come into intimate physical contact, no one would claim that this, by itself, has any special significance. For there is no sense in those signals themselves: their meanings to each lover lies in each one’s representations of the other one’s mind.[75] Nevertheless, although the B-Brain cannot directly perform a physical act, it still could affect the external world, albeit indirectly—by sending signals that change how A will react. For example, if A gets stuck at repeating itself, it might suffice for B just to interrupt.
Student: Like when I’ve misplaced my spectacles, I tend to keep seeking it on the same shelf. Then a silent voice reproaches me, suggesting that I look somewhere else.
In the ideal case, B could tell (or teach) A exactly what it ought to do. But even if B does not have such specific advice, it might not need to tell A what to do; it may suffice only to criticize the strategy A is using now.
Student: But what if I were walking across a road, when suddenly my B-brain said “Sir, you’ve repeated the same actions with your leg for more than a dozen consecutive times. You should stop right now and do something else.”
Indeed, that could cause a serious accident. To prevent such mistakes a B-Brain must have appropriate ways to represent things. This accident would not occur if B represent ‘walking to a certain place’ as a single extended act—as in “Keep moving your legs till you’ve crossed that street”—or in terms of progress toward some goal—as in, ‘keep reducing the remaining distance.’ Thus, a B-brain could act like a manager who has no special expertise about how to do any particular job—but still can give ‘general’ guidance like these.
If A’s descriptions seem too vague, B tells it to use more specific details.
If A is buried in too much detail, B suggests more abstract descriptions.
If what A is doing is taking too long, B tells it try some other technique.
How could a B-Brain acquire such skills? Some could be built into it from the start, but it should also be able to learn new techniques. To do this, a B-Brain itself may need help, which in turn could come from yet another level. Then while the B-Brain deals with its A-Brain world, that ‘C-Brain’ in turn will supervise B.
Student: How many levels does a person need? Do we have dozens or hundreds of them?
In Chapter §5 we’ll describe a model of mind whose resources are organized into of six different levels of processes. Here is an outline of what these might be: It begins with a set of instinctive reactions with which we are equipped with from birth. Then we become able to reason, imagine, and plan ahead, by developing ways to do what we call deliberative thinking. Yet later we develop ways to do “reflective thinking” about our own thoughts.—and still later we learn ways to self-reflect about why and how we could think about such things. Finally we start to think self-consciously about whether we ought to have done those things. Here is how that scheme might apply to Joan’s thoughts about that street-crossing scene:
Of course, this is oversimplified. Such levels can never be clearly defined—because, at least in later life, each of those types of processes may use resources at other levels of thought. However, this framework will help us to start to discuss the kinds of resources that adults use—and some ways that these might be organized.
Student: Why should there be any ‘levels’ at all—instead of just one large, cross-connected cloud of resources?
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This example is from Frederik Pohl’s prescient short story Day Million in his anthology, Day Million, Ballantine Books 1970 ISBN: 0330236067