Abstract: A language tutoring machine communicates with a user for teaching of a linguistic sub-system in a particular language. The language tutoring system comprises at least one computational module that functions to produce and comprehend utterances which employ the linguistic sub-system. The at least one computational module embodies two models which operationalizes the linguistic sub-system; a student model approximating a specified user's performance when producing and comprehending language involving the linguistic sub-system, and a teacher model which represents an archetypal configuration of the language-system. The teacher model and student model use the same formalisms, advantageously Incremental Recruitment Language (for conceptualising and interpreting) and Fluid Construction Grammar (for expression and parsing).