Chomsky s view of language performance and language competence and Tolman s distinction between learning and performance are examples of this separation. Psychology sacrificed sufficiency for generality. These approaches postulated an underlying mental representation that is constant from episode to episode, but is manifested with slight variability on any particular occasion.
Variability arises from something outside of the domain that psychology is intended to explain.
These underlying structural accounts cannot, by definition, explain the variability in performance because this variability is outside the purview of the theory. A symbol system does not need to know anything about what the symbols represent in order to function. Searle s Chinese room example shows that a system can operate well without any grounding. Without a homunculus to read the thoughts and translate them into action it is not clear how one does get from thought to action in a traditional symbolic representational view of cognition.