Also called linguistic performance, it is a term, together with competence, introduced by Noam Chomsky into generative and transformational grammar, and which forms the basis of psycholinguistics. It refers to specific utterances made by the native speaker of a language, including false starts, hesitations and speech errors. Broadly, speaking, competence and performance is a distinction between ‘know’ and ‘do’, and as consequence a person’s performance does not necessarily reflect their linguistic competence, perhaps a major feature of early language development. A similar, but not identical, distinction to that between competence and performance was put forward by Chomsky in the 1980s: I-language and E-language. I-Language is the focus of study in syntactic theory, where it is taken to be the mentally represented linguistic knowledge possessed by a native speaker of a language. As a mental object, most of linguistics then becomes a branch of psychology. E-Language covers all other notions of what constitutes a language (e.g., a body of knowledge or a set of behavioral habits shared by a community or group). According to Chomsky, this way of regarding language does not aid the study of innate linguistic knowledge (i.e., competence), even though it may be useful in other areas of study such as anthropological linguistics. The I-Language/E-Language distinction has not been without criticism.
See Competence (linguistics), Generative grammar approach, Linguistics, Language development, Mutual gaze, Psycholinguistics, Syntactic bootstrapping, Transformational grammar approach