This paper explores the consequences of the language-integrated nature of the bilingual mental lexicon for L2 sentence processing. It reviews L2 processing studies on gender agreement and syntactic structure building that test whether delays and cross-linguistic influence in lexical processing of the L2 lead to differences between L2 and L1 sentence processing. Slower L2 lexical processing delays and attenuates effects of syntactic structure in L2 sentence processing. In addition, cross-linguistic lexical influence can engender non-target patterns in L2 compared to L1 sentence processing. The paper spells out the assumptions and predictions of the Lexical Bottleneck Hypothesis, and I discuss how its insights can be incorporated into current models of L2 sentence processing.

This study investigates illicit object drop by elementary/lower-intermediate Japanese-speaking learners of English (JLEs). While it is reported in the literature (e.g., Wakabayashi & Negishi, 2003) that elementary/lower-intermediate JLEs frequently drop objects in obligatory contexts, why they produce such errors is still under debate. Using a forced-choice pointing task (Jiang & Haryu, 2014, 2016; Noble, Rowland & Pine, 2011), we investigate to what extent L1 transfer from Japanese (which allows extensive null arguments) is responsible for JLEs' object drop errors. The results of the experiments show that native Japanese speakers interpret sentences with one nominative argument (e.g., the man and the woman are gorping) differently in their L1 (Japanese) than in their L2 (English). Based on the results, it is concluded that L1 transfer has little effect on illicit object drop by JLEs.

This discussion article tries to explain the variability commonly observed in second language learners' use of grammatical morphemes. For almost two decades, second language studies have tried to specify THE right answer for why (even very advanced) L2 learners exhibit persistent difficulty in using inflectional morphemes, typically substituting bare forms for inflected forms. This line of inquiry is in fact misguided, as argued in previous work (e.g., Wakabayashi, 2013). We advance the present study in a more principled ‘analytic’ way, building on the framework of Distributed Morphology (Halle & Marantz, 1993), and it will be made clear that variability in second language use arises at multiple levels, due to incompleteness at Numeration within the Lexicon, at operations within morphosyntax, at Vocabulary Insertion, and at mechanisms of performance that function after linguistic operations have concluded.