Reconceptualising Processability Theory: Morphosyntactic Staging and Its Misalignment with Emergentist Acquisition Trajectories in L2 Arabic

Abstract

Processability Theory (PT), as originally formulated by Pienemann (1998), has long served as a foundational scaffold for sequencing L2 instructional interventions and predicting developmental readiness. However, growing empirical evidence drawn from longitudinal learner corpora in typologically distant languages challenges its universal morphosyntactic staging hierarchy. This study employs a mixed-methods corpus-driven design, analysing 1,240 learner-produced written and oral texts from advanced L2 Arabic learners across three institutional contexts in Morocco, Germany, and South Korea. Applying computational morphological parsing alongside think-aloud protocol analysis, we demonstrate that emergentist acquisition trajectories systematically diverge from PT-predicted stage sequencing, particularly at the noun phrase and verb agreement levels. Our findings call for a substantive revision of PT's cross-linguistic applicability and propose a revised emergentist-compatible staging model grounded in usage-based construction grammar frameworks.