Mind, Body, World- Foundations of Cognitive Science, 2013a

motto should hold. A principle of rationality, operating on propositional attitudes,
should offer real predictive power.
However, the logicism underlying the intentional stance leads to a serious problem
for classical cognitive science. This is because a wealth of experiments has shown
that human reasoners deviate from principles of logic or rationality (Hastie, 2001;
Tversky & Kahneman, 1974; Wason, 1966; Wason & Johnson-Laird, 1972). “A purely
formal, or syntactic, approach to [reasoning] may suffer from severe limitations”
(Wason & Johnson-Laird, 1972, p. 244). This offers a severe challenge to classical
cognitive science’s adherence to logicism: if thinking is employing mental logic,
then how is it possible for thinkers to be illogical?
It is not surprising that many attempts have been made to preserve logicism
by providing principled accounts of deviations from rationalism. Some of these
attempts have occurred at the computational level and have involved modifying the
definition of rationality by adopting a different theory about the nature of mental
logic. Such attempts include rational analysis (Chater & Oaksford, 1999) and probabilistic
theories (Oaksford & Chater, 1998, 2001). Other, not unrelated approaches
involve assuming that ideal mental logics are constrained by algorithmic and
architectural-level realities, such as limited memory and real time constraints.
The notion of bounded rationality is a prototypical example of this notion (Chase,
Hertwig, & Gigerenzer, 1998; Evans, 2003; Hastie, 2001; Rubinstein, 1998; Simon,
Egidi, & Marris, 1995).
The attempts to preserve logicism reflect the importance of the intentional
stance, and the semanticist’s motto, to cognitive science. Classical cognitive science
is committed to the importance of a cognitive vocabulary, a vocabulary that invokes
the contents of mental states (Pylyshyn, 1984).
3.9 Structure and Process
The physical symbol systems of classical cognitive science make a sharp distinction
between symbols and the rules that manipulate them. This is called the structure/
process distinction. For instance, in a Turing machine the symbols reside in one
medium (the ticker tape) that is separate from another medium (the machine head)
that houses the operators for manipulating symbols. Whatever the specific nature of
cognition’s universal machine, if it is a classical physical symbol system, then it will
exhibit the structure/process distinction.
In general, what can be said about the symbols that define the structure that
is manipulated by a physical symbol system? It has been argued that cognitive science’s
notion of symbol is ill defined (Searle, 1992). Perhaps this is because apart
from the need that symbols be physically distinctive, so that they can be identified
Elements of Classical Cognitive Science 85