Competence vs. performance

It’s all Chomsky’s fault apparently (Chomsky 1965, p. 4):

“We thus make a fundamental distinction between competence (the speaker-hearer’s knowledge of his language) and performance (the actual use of language in concrete situations). […] A record of natural speech will show numerous false starts, deviations from rules, changes of plan in mid-course, and so on. The problem for the linguist, as well as for the child learning the language, is to determine from the data of performance the underlying system of rules that have been mastered by the speaker-hearer and that he puts to use in actual performance.”

So the idea is that people are trying to do C but only manage to do P, because of various constraints. We (children, adults, theorists) see (imperfect) P, and want to infer C. We go to school and go through various rigmaroles to better approximate C. The same distinction is applied in reasoning. Various options: people are irrational (with respect to C); maybe C = P, if we look hard enough to see it. Or bright people have P = C. Or bright people want P = C.

What fascinates me in reasoning is the role played by small groups of experts who produce particular systems of reasoning—logical calculi, probabilistic machinery—along with proofs that they have properties which they argue are reasonable properties to have. Then others come along to use the systems. Hey, this looks like a good logic to know; maybe it’ll help make my arguments better if I use it. Maybe this probability calculus will make it easier to diagnose illness in my patients. And so forth. Then somebody else comes along and decides whether or not we’re consistent with a competence theory’s judgements, or whether we’re interpreting things a different way; whether another competence theory (application thereof) might be more appropriate for a given situation or a different psychological model of the situation.

Easy to get tied up in knots.

I don’t like the competence/performance distinction.  Maybe I just don’t like the words.  I’ll make a stab at expressing why one day…


Chomsky, N. (1965). Aspects of the Theory of Syntax. MIT Press.


One comment

  1. Peter Turney

    I don’t like the competence/performance distinction because it seems to be an excuse for ignoring empirical data. The best thing for linguistics, in my opinion, has been the increasing use of experimentation in computational linguistics.

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