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THE GRAND ILLUSION DOWN THE AGES AND UP FROM BIRTH

The neural circuits in our brain manage the beautifully coordinated and smoothly appropriate behavior of our body. They also produce the entrancing introspective illusion that thoughts really are about stuff in the world. This powerful illusion has been with humanity since language kicked in, as we’ll see. It is the source of at least two other profound myths: that we have purposes that give our actions and lives meaning and that there is a person “in there” steering the body, so to speak. To see why we make these mistakes and why it’s so hard to avoid them, we need to understand the source of the illusion that thoughts are about stuff.

In Chapter 8 we saw that the “thoughts” in the brain can’t be about anything at all, either things inside or outside the brain. The brain doesn’t store information that way. Rather, it stores information about the world in vast sets of input/output circuits that respond appropriately to one another and to their environment. These responses are so appropriate that it looks to us from the outside that other people’s brains are full of thoughts about the environment. From the inside, the illusion is even more powerful. So, where exactly does it come from?

To explain where the illusion that thoughts are about stuff comes from, we start with a simple case of the exquisite appropriateness of the input/output circuits to their environment. A fly passes in front of a frog’s visual field. The frog’s tongue flicks at the fly and brings it into its mouth. We watch this display and marvel at the frog’s ability, something we can’t do. We marvel at the fact that the frog knew that the little black thing in front of it was a source of food, knew exactly where it was headed, and knew where to flick its tongue in order to capture and eat it. Where did it store the information it needed to do this neat trick? In its neural circuitry, of course. But how did its neural circuits attain the ability to store this information?

The answer: natural selection. In the evolutionary past, there was strong selection for genes that build nerve circuits in the visual system that are stimulated to fire just by little black moving dots in the frog’s visual field. Big dots won’t do it, nor will motionless little ones. The advantage of such circuits is obvious. The only moving little black dots in the frog’s environment are insects it can eat. There was also selection for (genes that build) other circuits wired to take as inputs the visual system’s output and send their own output to other neural circuits that ultimately trigger tongue flicking. The process was just blind variation and environmental filtration. Over the evolutionary history of frogs, variation resulted in a few neural circuits connected to the eyes and the tongue in ways that happened to result in eating; most didn’t. The ones that did were selected for. There is nothing special about these neural circuits or different from other neural circuits that can do this job, other than their fortuitously connecting circuits from the eye to circuits for the tongue. Theses neurons aren’t any more about the fly than others that could do the same job but don’t because they are hooked up to other circuits. Frogs aren’t smart enough to learn how to flick flies by operant conditioning. Their survival is testimony to how finely Mother Nature (aka genetic natural selection) can tune the appropriateness of responses to the environment.

We are, of course, amazed at the environmental appropriateness of the frog’s tongue flicking. We say, “The frog knows where the fly is. There must be neurons in its brain that contain information about the fly’s speed and direction.” It’s perfectly natural for us to say this, but it’s an illusion that results solely from the environmental appropriateness of the dot-detection to tongue-flicking chain of neural inputs and outputs. The frog’s neural circuitry can’t be about the fly; they can’t be about