The Symbol Grounding Problem is related to the problem of how words get their meanings, and of what meanings are. The problem of meaning is in turn related to the problem of consciousness, or how it is that mental states are meaningful. The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... Consciousness is a quality of the mind generally regarded to comprise such key features as subjectivity, self-awareness, sentience, sapience, and the ability to perceive the relationship between oneself and ones environment. ...

A symbol is an arbitrary object, an element of a code or formal notational system. It is interpretable as referring to something, but its shape is arbitrary in relation to its meaning: It neither resembles nor is causally connected to its referent (see Saussure's L'arbitraire du signe). Its meaning is agreed upon and shared by convention. In communications, a code is a rule for converting a piece of information (for example, a letter, word, or phrase) into another form or representation, not necessarily of the same sort. ... Saussure Ferdinand de Saussure (November 26, 1857 - February 22, 1913) was a Swiss linguist. ...

Objects cannot be symbols autonomously; symbols are elements in symbol systems. The meanings of the symbols in a symbol system are systematically interrelated and systematically interpretable. Symbols are combined and manipulated on the basis of formal rules that operate on their (arbitrary) shapes, not their meanings; i.e., the rules are syntactic, not semantic. Yet the syntactically well-formed combinations of symbols are semantically interpretable. (Think of words, combined and recombined to form sentences that all have different meanings, but are systematically interrelated with one another.)

There is no symbol grounding problem for symbols in external symbol systems, such as those in a mathematical formula or the words in a spoken or written sentence. The problem of symbol grounding arises only with internal symbols, symbols in the head -- the symbols in what some have called "mentalese or the language of thought. External symbols get their meaning from the thoughts going on in the minds of their users and interpreters. But the internal symbols inside those users and interpreters need to be meaningful autonomously. Their meaning cannot just be based on a definition, because a definition is just a string of symbols, and those symbols need to be have meaning too. Definitions are meaningful if their component symbols are meaningful, but what can give their component symbols meaning? Fodors language of thought (LOT) hypothesis states that cognition is a process of computation over compositional mental representations. ... Fodors language of thought (LOT) hypothesis states that cognition is a process of computation over compositional mental representations. ...

If it were formal definitions all the way down, this would lead to a problem of infinite regress. If the meaning depended on an internal interpreter, then it would not be autonomous (and it makes no sense to say that the meanings of the symbols in my head depend on the interpretation of someome outside my head). An infinite regress is a series of propositions arises if the truth of proposition P1 requires the support of proposition P2, and for any proposition in the series Pn, the truth of Pn requires the support of the truth of Pn+1. ...

It is tempting to suppose that the meaning of a symbol that occurs inside an autonomous sensorimotor system (or robot) is whatever internal structures and process give that robot the ability to detect, identify, and interact with that symbol's external referent. But that would only be the symbol's grounding, not yet its meaning.

Designing a human-scale grounded symbol system that can pass the Turing Test (a robot whose performance capacities are equivalent to and indistinguishable from our own) is (or should be) the methodological and empirical goal of cognitive science. But would a Turing-scale robot's internal symbols have meaning rather than just grounding? The Turing test is a proposal for a test of a machines capability to perform human-like conversation. ... Rendering of human brain based on MRI data Cognitive science is usually defined as the scientific study either of mind or of intelligence (e. ...

The only difference between a grounded Turing-scale robot and us would be whether or not it was conscious (i.e., whether or not it had feelings). If it feels, then there is someone home in the robot for its internal symbols to be meaningful to. If the robot is not conscious, then its internal symbols have only grounding (in its sensorimotor capacity) but not meaning. Turing's test can be interpreted as showing that discovering what internal structures and processes are sufficient to ground symbols autonomously is as much we can ask of cognitive science; the other minds problem prevents us from being able to learn more.

References

• Stevan Harnad (1990) The Symbol Grounding Problem Physica D 42:pp. 335-346.
• Stevan Harnad (2003) Symbol-Grounding Problem in Encyclopedia of Cognitive Science. MacMillan: Nature Publishing Group.