Processability Theory and the role of morphology in English as a second language development: a longitudinal study

Abstract

This article tests a prediction made by Processability Theory (Pienemann, 1998; 2005) that morphological acquisition is the driving force in English as a second language (ESL) development. It first outlines the model of psycholinguistic processing assumed by Processability Theory and shows how stages fall out from it. It then presents the hypothesis that morphological information propels development before sentence-level processing at stage 5 and describes what this should predict for ESL learners. A study is then presented that tested these predictions on oral data collected from two Mandarin speaking, adolescent, ESL learners over one academic year. The study found the acquisition of structures both predicted and not predicted by Processability Theory. While the results afford some evidence consistent with the claims about stages of development, they also provide counter-evidence to the hypothesis that the acquisition of morphology drives development up to stage 5: one learner acquired the predicted syntax for stages 3 and 4 without the morphology, and both learners acquired syntactic structures before associated morphology. Indeed, the findings suggest that the acquisition of morphology, and syntax, varies with learner orientation. To explain these findings, the article presents a proposal that draws on both Processability Theory and generative approaches to second language acquisition (SLA), and concludes by considering the implications of the study.