Learn the Definition of Mental Grammar and How it Works

Mental grammar is the generative grammar stored in the brain that allows a speaker to produce language that other speakers can understand. It is also known as competence grammar and linguistic competence. It contrasts with linguistic performance, which is the correctness of actual language use according to a language's prescribed rules. 

Mental Grammar

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What Is Psycholinguistics?

By Richard Nordquist

The concept of mental grammar was popularized by American linguist Noam Chomsky in his groundbreaking work "Syntactic Structures" (1957). Philippe Binder and Kenny Smith noted in "The Language Phenomenon" how important Chomsky's work was: "This focus on grammar as a mental entity allowed enormous progress to be made in characterizing the structure of languages." Related to this work is Universal Grammar or the predisposition for the brain to learn the complexities of grammar from an early age, without being implicitly taught all the rules. The study of how the brain actually does this is called neurolinguistics.

"One way to clarify mental or competence grammar is to ask a friend a question about a sentence," Pamela J. Sharpe writes in "Barron's How to Prepare for the TOEFL IBT." "Your friend probably won't know why it's correct, but that friend will know if it's correct. So one of the features of mental or competence grammar is this incredible sense of correctness and the ability to hear something that 'sounds odd' in a language."

It's a subconscious or implicit knowledge of grammar, not learned by rote. In "The Handbook of Educational Linguistics," William C. Ritchie and Tej K. Bhatia note,

"A central aspect of the knowledge of a particular language variety consists in its grammar—that is, its implicit (or tacit or subconscious) knowledge of the rules of pronunciation (phonology), of word structure (morphology), of sentence structure (syntax), of certain aspects of meaning (semantics), and of a lexicon or vocabulary. Speakers of a given language variety are said to have an implicit mental grammar of that variety consisting of these rules and lexicon. It is this mental grammar that determines in large part the perception and production of speech utterances. Since the mental grammar plays a role in actual language use, we must conclude that it is represented in the brain in some way.
"The detailed study of the language user's mental grammar is generally regarded as the domain of the discipline of linguistics, whereas the study of the way in which the mental grammar is put to use in the actual comprehension and production of speech in linguistic performance has been a major concern of psycholinguistics." (In "Monolingual Language Use and Acquisition: An Introduction.")

Prior to the early 20th century and previous to Chomsky, it wasn't really studied how humans acquire language or what exactly in ourselves makes us different from animals, which don't use language as we do. It was just classified abstractly that humans have "reason," or a "rational soul" as Descartes put it, which really doesn't explain how we acquire language, especially as babies. Babies and toddlers don't really receive grammar instruction on how to put words together in a sentence, yet they learn their native tongue just by exposure to it. Chomsky worked on what it was that was special about human brains that enabled this learning.