In 1998, Pienemann proposed his processability theory (PT), a novel psycholinguistic theory of second language (L2) grammar development, based primarily on German, English, and Swedish data. Ten years later, PT has grown substantially, expanding its scope in three directions. First, new L2s as diverse as Chinese, Japanese, Italian, and Arabic have strengthened the theory typologically. Second, new learning conditions and applications have enriched the scope of PT beyond teachability and testing, to include bilingual SLA, language impairment, first language transfer, pidgin and creole languages, rapid profiling, and written production. Third, and most importantly, the architecture of PT has been expanded by the addition of a second set of principles that contributes to the formal modeling of levels of processability—namely, the mapping of argument-structure onto functional structure in lexical mapping theory. These additional principles resolve some problems left unsolved by the original (Pienemann, Reference Pienemann1998) version of PT and account for new issues raised by less configurational languages than English, such as Italian and Japanese (Pienemann, Di Biase, & Kawaguchi, Reference Pienemann, Di Biase, Kawaguchi and Pienemann2005). Thus, this theory can now deal not only with the development of obligatory morphosyntactic structures acquired following an implicational pattern but also with choices at the structural-pragmatic interface. These choices are also anchored on the structural development of the learner and are hierarchically ordered: from canonical to noncanonical, from least marked to more marked choices.

This work is an excellent summary of the current stage of the development of PT itself and an illustration of the range of issues it covers. Part 1 serves as an introduction to PT and includes chapters that present (a) the whole theory by Pienemann; (b) an excellent overview by Fabbri of lexical functional grammar, the framework in which PT has chosen to represent grammatical facts; and (c) a discussion of PT’s explanatory power by Keßler, who demonstrates how PT can successfully address 6 of the 10 key issues identified by VanPatten and Williams (Reference VanPatten and Williams2007) as needing explanation by SLA theories. Part 2 addresses issues new to PT. Kawaguchi shows how PT can neatly accommodate into its developmental schedules the encoding of grammatical relations in typologically different languages (e.g., English, a head-marking language; Arabic and Italian, two pro-drop languages; and Japanese, a dependent-marking language). Zhang tests two positions on language transfer—the full transfer/full access model (Schwartz & Sprouse, Reference Schwartz and Sprouse1996) and PT’s developmentally moderated transfer hypothesis (Pienemann, Di Biase, Kawaguchi, & Håkansson, Reference Pienemann, Di Biase, Kawaguchi and Pienemann2005)—and shows how her longitudinal Chinese L2 data support the latter. Rahkonen and Håkansson report on the impact of formal and informal learning on written production data and discuss the role of infrequent structures in the input for explaining their late emergence in Swedish L2. Part 3 presents three studies, each on classroom applications. Keßler and Keatinge refine the English L2 rapid profiling procedures in which trained analysts can efficiently assess where learners stand on the developmental trajectory. Di Biase convincingly proves, with primary school Italian L2 data, how even a small amount of form-focused communicative activities can speed up the learning process substantially, provided the targeted grammar features are developmentally moderated, as defined by PT. Finally, Lenzing analyses two textbooks for teaching English and reports that the sequence in which these books introduce grammatical structures renders them unprocessable in PT terms and therefore unlearnable.