This article examines the knowledge of topic and subject particles in heritage speakers and L2 learners of Japanese and Korean. We assume that topic marking is mediated at the syntaxinformation structure interface, while subject marking pertains to narrow syntax. In comparing phenomena mediated at different levels of linguistic organization, we provide evidence for the hypothesis that information structure-level phenomena present greater challenges for bilingual speakers than those mediated within syntax. While these results may be interpreted as evidence of generalized interface-related deficits, we show that such a global explanation is not supported.Instead, a more nuanced account is developed, based on the recognition of different types of topic (anaphoric, generic, and contrastive) and different types of subject (descriptive and exhaustive). Under the proposed account, the non-native speakers' deficits follow from three unrelated effects: the status of topic as an interface category, structural complexity, and the memory demands necessary for its interpretation in context.
Introduction
Interfaces: The integration problem1 This project was supported in part by grants from Center for Advanced Study of Language (CASL) at the University of Maryland and from NSF (SMA-1429961) to the second author. Any opinions, findings, conclusions or recommendations expressed in this material are those of the authors. We would like to thank Sun-Hee Bae, Miwako Hisagi, Kenneth Mai, Hiroki Nomoto, Aika Taguchi, and three anonymous reviewers for helpful comments on this paper. All errors are our responsibility.
2Heritage language and second language (L2) acquisition represent two distinct pathways to adult bilingualism. They differ along a number of dimensions, including the specific circumstances of language exposure and the nature of competence deficits across different language modules. As early bilinguals, heritage speakers begin the acquisition of a socially non-dominant language in a family setting, and in this respect, their experience with the target language compares to that of early L1 learners, at least at the outset of the language acquisition process. The main difference is that heritage speakers' L1 language acquisition is subsequently interrupted by exposure to another language. Adult L2 learners, on the other hand, are late bilinguals whose exposure to the non-dominant language typically takes place in an instructed setting.Despite these differences in acquisition scenarios, both groups of speakers similarly fall short of exhibiting complete mastery of the target language. Even at the highest levels of proficiency, both populations remain in a state of near-native attainment, deviating from target native grammars represented by the monolingual baseline. In particular, early and late bilinguals (heritage speakers and L2 learners alike) have been reported to display deficits in the domain of inflectional morphology and narrow syntax, and both groups also seem to have difficulties with discourse-level phenome...