Is the brain a computer?

Overview

This course focuses on computational neuroscience as the study of how nervous systems perform computations and process information. But is the brain a computer? Or is this conception an analogy drawn from modern technology that we (perhaps inappropriately) apply to the functional organization of nervous systems?  What is a computer, exactly? And which brain (i.e., central nervous system) do you have in mind? Human? Mouse? Nematode?

Assignment

  • Read or listen to “The Empty Brain” by Robert Epstein (4200 words, 25 minutes). Then, respond in writing and upload your thoughts to Blackboard (see writing prompts and further instructions below).
  • Watch the video “Turing Machines Explained with a Pencil” (below).
  • Read and consider the quote from Hilary Putnam (below) about the importance of computers/machines in the philosophy of mind. 

Consider the following diametrically apposed position statements.

Churchland affirms that the brain is a computer.

The expression “Computational Neuroscience” reflects the possibility of generating theories of brain function in terms of the information-processing properties of structures that make up nervous systems. It implies we ought to be able to exploit the conceptual and technical resources of computational research to help find explanations of how neural structures achieve their effects, what functions are executed by neural structures, and the nature of representation by states of the nervous system.  [Churchland et al. 1993]

Epstein denies that the brain is a computer:

We don’t store words or the rules that tell us how to manipulate them. We don’t create representations of visual stimuli, store them in a short-term memory buffer, and then transfer the representation into a long-term memory device. We don’t retrieve information or images or words from memory registers. Computers do all of these things, but organisms do not.

… [C]omputers really do operate on symbolic representations of the world. They really store and retrieve. They really process. They really have physical memories. They really are guided in everything they do, without exception, by algorithms.

Humans, on the other hand, do not – never did, never will. Given this reality, why do so many scientists talk about our mental life as if we were computers?  [Epstein 2016]

What are we to make of this disagreement?

Writing prompts (200-300 words each).

Type your answers or write neatly. Then, scan and upload your response to the class Blackboard site. Write in a professional manner, but from your personal perspective (as you would in a journal) with the understanding that I will read what you write. Write out the prompt prior to your response, so both question and answer are there when you review your notes.

  • Our definition of computational neuroscience (see above) is prima facie incompatible with main thrust of Robert Epstein’s essay. Choose several statements from “The Empty Brain” and explain why you agree or disagree.
  • We discussed in class how “information” and “information processing” are vague terms that must be unpacked before we can have a productive conversation about the brain and computation. Can you think of any other relevant concepts that need closer examination?
  • Give a few examples of metaphors in the science of human physiology and ordinary human language that involve technology. “The heart is a pump.” “Sorry, I got my wires crossed.”
  • How has the way people think about our bodies changed over the centuries? What are the potential problems associated with using the metaphor of a machine for the human body?

Come to the next class prepared to share what you have written with other students!

Turing machines explained with a pencil.

Hilary Putnam on computers/machines in the philosophy of mind

What is the importance of computers/machines in the philosophy of mind?  I think that machines have both a positive and a negative importance.  The positive importance of machines was that it was in connection with machines, computing machines in particular, that the notion of functional organization first appeared.  Machines forced us to distinguish between an abstract structure and its concrete realization. Not that the distinction came into the world for the first time with machines.  But in the case of computing machines, we could not avoid rubbing our noses against the fact that what we had to count as to all intents and purposes the same structure could be realized in a bewildering variety of different ways; that the important properties were not physical-chemical.  That the machines made us catch on to the idea of functional organization is extremely important.  The negative importance of machines, however, is that they tempt us to oversimplification.  The notion of functional organization became clear to us through systems with a very restricted, very specific functional organization.  So the temptation is present to assume that we must have that restricted and specific kind of functional organization.  [Putnam 1975, p. 299-300 in our reading: Philosophy and our mental life.]

Further Reading

Savage, John E. (1998). Models Of Computation: Exploring the Power of Computing. Addison-Wesley.  [PDF]