ABSTRACT
In contrast to complexity and accuracy, which may pertain to oral and written second language L2 performance, fluency is first and foremost a measure of spoken language, even though writing research also uses measures of fluency. Such measures make it less difficult to identify and disentangle the sub dimensions of fluency from accuracy and complexity in written performance because they allow reviewing the process of writing fluency and not a product only. Measures of complexity, accuracy, fluency comes in three types of forms: frequency counts of a specific linguistic unit, ratio measures, that divide a specific unit by the total number of another unit and indices, which are calculations of a score by means of a more complex formula. Using hierarchical linear modelling grammatical complexity, accuracy, and fluency shows steady linear growth while lexical variety revealed a nonlinear trajectory. Dialogic performance in both populations was characterized by lower grammatical complexity, but higher accuracy and fluency.
