The Problems of Scope and Classification

The field of second language acquisition (SLA) has long sought relevant factors to explain differential attainment for early and late learners. Since the appearance of Lenneberg's Biological Foundations of Language (1967), the idea of a critical period for language learning has guided a great deal of the research on second language acquisition. Though Lenneberg made little specific mention of SLA, his critical period hypothesis has evolved into a full-blown theory for the field, often assumed to be a 'unitary account of non-native like outcomes' (Birdsong, 1999: 9). Still, the question remains why late language learners typically perform in notably 'non-native' ways. In the search for answers, we too rarely recognize the highly individual and complex nature of the endeavor. This is an especially salient issue given that SLA is most often an uninstructed, i.e. non-classroom, process among immigrants to foreign lands who face harsh social and economic conditions, possibly remaining culturally isolated for years.

Given this context of great challenge, many fall far short of a native speaker ideal, while others succeed beyond all expectations. By all accounts, we cannot yet explain either extreme of the success scale: entrenched fossilization and exceptional learning. The empirical evidence points to no specific faculty or mechanism in either the neurological or cognitive realm to explain exceptional performance in L2 (Obler, 1989; Schneidermann, 1991 as cited in Birdsong & Molis, 2001). Why, then, do more learners not attain to this level? In a recent review of cognitive research on bilingualism, Gonzalez and Schallert (1999) confirm that language processing is a multi-level task, incorporating knowledge from structural, semantic, discursive and cultural levels of language.