The aim of this paper is to present a review of psycholinguistic studies designed to examine the impact of transcription skills in written text compositions and to compare psycholinguistic and linguistic results about the issue of number agreement, with some didactical implications. In psycholinguistics, the issue of the impact of handwriting and spelling skills on the quality and management of written text production was renewed by developmental models of composing. Handwriting and spelling appeared to be as two main cognitive constraints during text production in any novice writer. A great number of research was devoted to assess the influence of handwriting and/or spelling processes both on the quality of the produced text and on the on line management of the other composition processes. However, spelling production is not only linked to the writer's working memory resources. In the field of linguistics, and with another methodological approach, research indeed shows how correct agreements in French depend on children's conceptions on morphology, syntax and morphography.