Published online by Cambridge University Press: 07 November 2008
Variability, both systematic and nonsystematic, has been the subject of much debate in recent years in the study of learner interlanguage. This article presents empirical evidence from a longitudinal study of a small group of advanced learners of French. Variability is noticeable throughout the period of learning of a particular structure in French. Nonsystematicity observed in individual learners' performance is explained in the light of developmental stages such as those put forward in Gatbonton's diffusion model. When looked at in terms of developmental processes, nonsystematic variability becomes an essential element of progress. Patterns of development are observed across the subjects, and learning can thus be seen to follow a systematic route.