Piero Scaruffi(Copyright © 2013 Piero Scaruffi | Legal restrictions )
These are excerpts and elaborations from my book "The Nature of Consciousness"
The Road from Neurons to Symbols
Computational models of neural networks have greatly helped in understanding how a structure like the brain can perform. Computational models of cognition have improved our understanding of how cognitive faculties work. But neither group has developed a theory of how neural processes lead to symbolic processes, of how electro-chemical reactions lead to reasoning and thought.
A bridge is missing between the physical, electro-chemical, neural processes and the macroscopic mind processes of reasoning, thinking, knowing, etc., in general, the whole world of symbols. A bridge is missing between the neuron and the symbol. Several philosophers have tried to fill the gap.
The "harmony" theory proposed by the US computer scientist Paul Smolensky is an effort in this direction. Smolensky worked out a theory of dynamic systems that perform cognitive tasks at a subsymbolic level. The task of a perceptual system can be viewed as the completion of the partial description of static states of an environment. Knowledge is encoded as constraints among a set of perceptual features. The constraints and features evolve gradually with experience. Schemata are collections of knowledge atoms that become active in order to maximize what he calls "harmony". The cognitive system is, de facto, an engine for activating coherent assemblies of atoms and drawing inferences that are consistent with the knowledge represented by the activated atoms. A harmony function measures the self-consistency of a possible state of the cognitive system. Such harmony function obeys a law that resembles simulated annealing (just like the Boltzmann machine): the best completion is found by lowering the temperature to zero.
The US philosopher Patricia Churchland aims at a unified theory of cognition and neurobiology, of the computational theory of the mind and the computational theory of the brain. According to her program, the symbols of Fodor's mentalese should be somehow related to neurons, and abstract laws for cognitive processes should be reduced to physical laws for neural processes.
Nonetheless, the final connection, the one between the connectionist model of the brain and the symbol-processing model of the mind, is still missing.
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