Processability Theory
Processability Theory (PT), developed by Manfred Pienemann (1998, 2005), predicts that L2 learners can only produce and comprehend linguistic structures that their current language processor can handle. The theory builds on Levelt's (1989) speech production model and is formalized using Lexical-Functional Grammar (Bresnan, 2001).
The Processing Hierarchy
PT proposes five hierarchical stages, each defined by the type of grammatical information exchange (feature unification) the learner can perform. Each stage is a prerequisite for the next:
| Stage | Procedure | Example (English) |
|---|---|---|
| 1 | Lemma access | Single words, formulae (hello, my name is) |
| 2 | Category procedure | Lexical morphemes, canonical word order (SVO) |
| 3 | Phrasal procedure | Phrasal agreement (these dogs, is walking) |
| 4 | S-procedure | Inter-phrasal information exchange (subject-verb agreement: he walks) |
| 5 | Subordinate clause procedure | Main-subordinate clause linkage, embedded questions |
At any point, the hierarchy is "cut off" where processing prerequisites are missing — the learner maps conceptual structures directly onto surface form below that threshold.
Teachability Hypothesis
Pienemann's (1985) earlier Teachability Hypothesis follows directly: instruction can only promote acquisition of structures the learner is developmentally ready to process. Teaching beyond the learner's current stage is ineffective. This constrains PPP and any synthetic syllabus that sequences structures by perceived difficulty rather than processing readiness.
Empirical Support and Critique
PT has been tested across multiple L2s (English, German, Swedish, Japanese, Italian) with generally supportive results for the predicted stages. Critics note the theory focuses narrowly on morphosyntax and says little about lexical, phonological, or pragmatic development. It also does not account well for individual variation or the role of input frequency.
References
- Pienemann, M. (1998). Language Processing and Second Language Development: Processability Theory. John Benjamins.
- Pienemann, M. (2005). Cross-Linguistic Aspects of Processability Theory. John Benjamins.
- Levelt, W.J.M. (1989). Speaking: From Intention to Articulation. MIT Press.