Computers are sometimes characterized as symbol manipulators.

• Computers read input, normally stored as symbols that are represented as some sequence of 0's and 1's. (Sensors translate typing, temperature, or other input into a symbolic form.)
• Computers follow rules to manipulate those 0's and 1's to yield more symbols, represented as sequences of 0's and 1's.
• Computers output these sequences of 0's and 1's, representing the output in symbolic form as text, graphics, or sound. (A robot could translate the output sequences/symbols into physical forms.)

Altogether, computer processing involves representing symbols in some way, manipulating those symbols, and outputting the results symbolically. That is, at a fundamental level, computers symbol manipulators.

Results from theoretical computer science show that expanding the symbols from 0's and 1's to any richer symbolic system (e.g., the English alphabet) does not affect the problems that computers can solve. Some symbolic systems may be more convenient than others, but any system with at least two symbols has the same representation power as any other system.

Summary of Computer Processing: Computers process by manipulating symbols.

Processing by Humans

Many aspects of computer processing seem analogous to how the brain works:

• Our bodies collect input through sensory receptors (e.g., taste buds, temperature and pressure cells).
• Neurons translate input into electro-chemical pulses that are transmitted to the brain.
• Neurons within the brain react to these pulse stimulae.
• After a sequence of neuron interactions, neurons may transmit pulses that control muscles and other "output" devices.

Fundamental question: Does processing within the human brain involve anything beyond this manipulation of symbols?

The Symbol System Hypothesis

Answer: No, the above outline completely explains human thinking!

Certainly, the Symbols System Hypothesis is consistent with view of determinism, behaviorism, and the perspectives of B. F. Skinner.

If the Symbols System Hypothesis is incorrect,

• What might be missing; what other part(s) of brain processing should be added?
• What evidence supports the identified missing pieces?

created 8 January 2007 last revised 9 January 2007

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