Chapter 6. Processability Theory
This chapter presents a psycholinguistic account of the developmental sequences found in second language acquisition (SLA). Building on Levelt’s (1989) model of speech production, Processability Theory (PT: Pienemann 1998, 2005) proposes that the order in which morpho-syntactic structures are acquired will be controlled by the processing requirements of those structures. The cross-linguistic validity of PT will be illustrated by the analysis of learner data in some typologically diverse languages. The findings show that the hierarchical sequence of processing procedures is similar across languages, if the emergence criterion is used, and also that the influence of any previously acquired is constrained by the processability of the structures. The implications of these findings for SLA research and profiling will be discussed.