Analyzing variability in L2 ultimate attainment

Ultimate attainment is typically more heterogeneous among second-language (L2) learners than among native speakers (e.g. Bley-Vroman, 1990). The present study offers a suite of simple analytical procedures aimed at exploring types and loci of variability in L2 attainment vis-à-vis those in the corresponding first language (L1), with special attention to certain learner-external factors that might condition such variabilities. To demonstrate the methods and their potential, we apply these procedures to learner and native acceptability judgment data published in Birdsong (1992). Under means analyses of item ratings and coefficients of variation (CV), a group of adult Anglophone learners of L2 French (ENS) are found to resemble native French controls (FNS). In contrast, under correlational analyses of ratings and CVs, ENS resemble FNS on grammatical items, but diverge on ungrammatical items. Correlational and means analyses of both CV and acceptability ratings reveal that ENS-FNS convergence is not predictable from the degree of FNS ratings variability, contra DeKeyser (2012). For both groups, we observe an interaction between FNS ratings variability and the grammatical status of items (ungrammatical vs. grammatical). Finally, for neither group do we find a relationship between the order of item presentation and ratings severity or CVs. We present our perspectives as a road map for future analyses of variabilities inherent in language learning outcomes.