The term linguistic competence refers to the unconscious knowledge of grammar that allows a speaker to use and understand a language. Also known as grammatical competence or I-language. Contrast with linguistic performance.
As used by Noam Chomsky and other linguists, linguistic competence is not an evaluative term. Rather, it refers to the innate linguistic knowledge that allows a person to match sounds and meanings. In Aspects of the Theory of Syntax (1965), Chomsky wrote, "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)."
Examples and Observations
"Linguistic competence constitutes knowledge of language, but that knowledge is tacit, implicit. This means that people do not have conscious access to the principles and rules that govern the combination of sounds, words, and sentences; however, they do recognize when those rules and principles have been violated… For example, when a person judges that the sentence John said that Jane helped himself is ungrammatical, it is because the person has tacit knowledge of the grammatical principle that reflexive pronouns must refer to an NP in the same clause." (Eva M. Fernandez and Helen Smith Cairns, Fundamentals of Psycholinguistics. Wiley-Blackwell, 2011)
Linguistic Competence and Linguistic Performance
"In Noam Chomsky's theory, our linguistic competence is our unconscious knowledge of languages and is similar in some ways to Ferdinand de Saussure's concept of langue, the organizing principles of a language. What we actually produce as utterances is similar to Saussure's parole, and is called linguistic performance. The difference between linguistic competence and linguistic performance can be illustrated by slips of the tongue, such as 'noble tons of soil' for 'noble sons of toil.' Uttering such a slip doesn't mean that we don't know English but rather that we've simply made a mistake because we were tired, distracted, or whatever. Such 'errors' also aren't evidence that you are (assuming you are a native speaker) a poor English speaker or that you don't know English as well as someone else does. It means that linguistic performance is different from linguistic competence. When we say that someone is a better speaker than someone else (Martin Luther King, Jr., for example, was a terrific orator, much better than you might be), these judgements tell us about performance, not competence. Native speakers of a language, whether they are famous public speakers or not, don't know the language any better than any other speaker in terms of linguistic competence." (Kristin Denham and Anne Lobeck, Linguistics for Everyone. Wadsworth, 2010)
"Two language users may have the same 'program' for carrying out specific tasks of production and recognition, but differ in their ability to apply it because of exogenous differences (such as short-term memory capacity). The two are accordingly equally language-competent but not necessarily equally adept at making use of their competence.
"The linguistic competence of a human being should accordingly be identified with that individual's internalized 'program' for production and recognition. While many linguists would identify the study of this program with the study of performance rather than competence, it should be clear that this identification is mistaken since we have deliberately abstracted away from any consideration of what happens when a language user actually attempts to put the program to use. A major goal of the psychology of language is to construct a viable hypothesis as to the structure of this program… " (Michael B. Kac, Grammars and Grammaticality. John Benjamins, 1992)