Research in cognitive science may focus on one or more “levels of explanation”: the metaphorical level, drawing on common sense; the conceptual level, in which verbal concepts are defined as part of a network of relationships (neural, molecular or even biochemical level, etc.).
The research and applications presented in this book are situated on the conceptual level, where the human cognitive system is seen as a system manipulating symbols. The concepts used at this level are structured by a network of relationships, and the expected observables obtained from the symbol manipulation process may be relatively complex behaviors. A classic example would be the series of calculations produced by a high-school freshman solving a factorization problem in math.
We make no attempt to precisely define the term “symbol”, the subject of intense debates throughout the 1970s and 1980s which remain unresolved to this day. We shall simply observe that at a “finer” level of explanation, for example neural level, cognitive processes are described using concepts of “activation”, “inhibition”, etc.; on the other hand, neither neurons nor neural areas “manipulate” anything. At the explanatory level chosen here, a symbol is a representation of a thing. For example, the word “hand” represents a part of the human body; this body part may also be represented by a drawing, a sign, etc.
The level of symbol manipulation considered in the works of this series comes after the treatment of ...