God Soul Mind Brain

among them. White Eve, for example, knew nothing about Black Eve. She was not conscious of anything Black Eve thought or did.

    I am arguably venturing onto shaky ground here, since the disorder is controversial. It is easy to dismiss the sensational claims as pseudoscience. But I think it is possible to understand how such a thing could in principle exist more or less as it is described. Normally the social machinery builds perceptual models of other people’s minds. A model of a mind contains a vast, linked set of information on personality, on goals, on intentions, on agendas. It also contains information on the contents of the person’s awareness. The nature of the model is that it is internally linked—it is “associative”—meaning that when one part of it is accessed, the rest comes too. The model is the means by which we understand the other person’s mind. The social machinery also builds a perceptual model of the self. What is to stop it from building more than one perceptual model of the self, each with its own personality, each with its own information on the contents of conscious awareness? When you are asked whether you are consciously aware of A or B or C, if you have multiple self models, your answer will depend on which self model is searched. How such a disorder—having one’s social machinery create more than one self model—could possibly develop in the first place is a separate question of the life history of the patient. Nobody knows the answer to that question. But once we understand consciousness to be a perceptual model, it follows that the machinery could in principle support multiple competing models that alternate due to the process of multistable perception.

Boxes and arrows

    I drew a diagram to try to get across the main point.

    Diagram 4-1

    Biology is messy, and a simple diagram is never truly accurate. As I explain the various parts of this diagram, the scientist in me will point out caveats and problems. But do not take this self-criticism as a lack of faith in the hypothesis. It is simply the knee-jerk habit of a scientist. I have chosen to leave in these criticisms, because I think the underlying ideas survive them and come out stronger as a result. Despite all the caveats, this simple diagram captures the basic idea.

    Diagram 4-1 shows a crude drawing of different brain systems depicted as boxes. The boxes are connected by arrows indicating the flow of information. This method of diagramming the brain as a set of boxes with arrows is a traditional method, but obviously leaves a great deal to be desired. Probably a better depiction of a brain area would be a cloudy collection of hundreds of millions of dots, each dot representing a nerve cell (a neuron). Instead of arrows connecting brain areas, thin lines would connect the neurons. If brain area A is densely connected to brain area B, that relationship would be depicted in the ideal diagram as a large number of spidery lines connecting the neurons of cluster A to the neurons of cluster B. Such a diagram would be much closer to the real architecture of the brain. However, since that level of detail and complexity is prohibitive in a diagram, and since the purpose of a diagram is to show underlying concepts by simplifying the details, the boxes and arrows will do. I hope you will be patient with the explanation below. If it sounds complicated and full of too many box this and box that, just look back at the diagram and the words should become clear.

    The diagram includes boxes for two different types of perception: visual perception and social perception. Of course there are many other types of perception, but the diagram gets across the basic idea that different pieces of machinery in the brain compute different aspects of perception. The diagram also contains two overlapping boxes to represent cognition. The reason why these boxes are overlapping is that the neuronal machinery for cognition seems to be multipurpose. Some of the same machinery almost certainly comes into play for visual cognition as for social cognition.

    The separation of functions into four boxes is clearly a simplification. Moreover, the diagram leaves out most of the brain. It lacks boxes for touch, hearing, and smell, for controlling hand movement, for processing language, for reward and emotion, for memory. But despite all these simplifications, it gets across some preliminary, first-order ideas.

    Social perception (box 1) receives