Testing Processability Theory in L2 Spanish: Can readiness or markedness predict development?

The goal of this dissertation is to test the five stages of Processability Theory (PT) for second language (L2) learners of Spanish and investigate how instruction can facilitate the development through the stages. PT details five fixed stages in the acquisition of L2 morphosyntax based on principles of speech processing (Levelt, 1989) and modeled on Lexical- Functional Grammar (LFG) (Kaplan & Bresnan, 1982; Bresnan, 2001). In addition, two models that predict how instruction can affect staged language development are tested: the Teachability Hypothesis (Pienemann, 1984, 1989), which says that instruction will only be effective if aimed at the next developmental stage and Projection Model (Zobl, 1983, 1985), which claims that instruction on more marked items can project to less marked, related items. In Study 1, the specific stages for L2 Spanish morphology and syntax were proposed and tested on a cross-sectional corpus of conversational data by learners (n=21) with L1 English. Implicational scaling confirmed the five stages for the syntax and morphology with 100% scalability. Syntax was also found to emerge before morphology at all five stages. Studies 2 and 3 tested the effect of instruction aimed at Stages 3, 4 and 5 for beginning (first and second semester) learners of Spanish ( N=57). Learners' oral production and stage gains were measured between a pre-test, a post-test two days after instruction, and a delayed post-test three weeks later. Learners' production of the target structures increased after instruction on the next, next + 1 or next + 2 stages, while the control groups made no significant changes. These results present counter-evidence to the prediction of the Teachability Hypothesis that instruction only on the next stage can aid learners to advance to subsequent developmental stages. Overall, the results offer further cross-linguistic support for the PT hierarchy, while refuting one of its corollaries, the Teachability Hypothesis