As her career developed, Bybee's contributions moved progressively from formalist theories towards a functional and cognitive perspective, incorporating insights from morphology, semantics, syntax, child language acquisition and historical linguistics.

In the early and mid-70's, Bybee proposed that the connection between the abstract phonological representation of a word and the actual forms experienced by language users was a more direct one than previously postulated.

[3] The proposal that the structure of language derives from actual communication rather than from abstract rules wired in the brain represented a major departure from the mainstream linguistics, an idea Bybee pursued in all her subsequent work.

In 1985, Bybee published her influential volume Morphology: A study of the Relation between Meaning and Form, in which she uncovered semantic regularities across 50 genetically and geographically diverse languages.

Alongside linguists Dan Slobin and Carol Moder, Bybee's work helped popularize the concept of mental schemas (or schemata) to explain grammatical structure, especially in terms of connections between morphological forms within a paradigm.

Words with high lexical strength are easy to access, serve as the bases of morphological relations and exhibit an autonomy that makes them resistant to change and prone to semantic independence.