Hunting the Homunculus

In the endless search for self-knowledge through the centuries a central question has been how we come to have any knowledge at all. Common sense has no doubts: as John Locke put it “perception is the first step towards knowledge, and the inlet of all the materials of it.” But if this is so where does the news come from, and how and where is it received? Does it arrive in ready-made packets at some place in the brain where it is collected by a central agent, the mind, soul, or some hidden homunculus? Worse still, what is it that perception receives? Where do the facts come from? Are they all out there in the form of objects and events in a real world?

These are classical questions for philosophy, but recent approaches to them have included studies of the brain by neuroscientists and the construction by cognitive scientists of theoretical and practical models of perception and thinking. The theory of neural Darwinism as proposed by Gerald Edelman of Rockefeller University brings these two approaches together. He gives a detailed account of brain activity, and provides computer models of the principles that are involved. He claims to show in this theory how selection under the influence of experience is the principle by which brains accomplish their feats of perception, learning, and memory. Edelman wisely leaves to later the application of these ideas to the general problems of consciousness, emotion, and language.

In spite of this restraint the theory does in fact give promise of providing understanding of some problems that interest us very much, such as how there can be recovery of function after damage to the brain. The theory also provides a view of how we come to analyze the world, without postulating the presence of a non-material central agent or homunculus. This is a problem that is rarely faced by neuroscientists, who may study nerve cells, conditioned reflexes, cortical areas, or brain waves without deciding who or what it is that “uses” these to produce behavior, much less mentality. In spite of a vast amount of new information there is still no generally accepted view of how the brain functions as a whole, and most physiologists would probably say that it is not realistic even to think of such a thing. The very idea smacks of the “homunculus fallacy.” Apart from metaphysical considerations, anatomists and physiologists do not find any evidence for central agents, so they are left without any general theory at all.

Perhaps the reason for this serious failure is that neuroscientists mostly think about individual units but not about the population of neurons and their connections, the synapses in the brain. Populations are the very subject matter of Edelman’s theory of neural Darwinism. As the name suggests this theory holds that the organization of the brain is achieved by competition for survival between neurons, and hence by selection of the nervous connections that are effective for survival. Nature does not produce its marvelous results …

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