By nearly all accounts, the mastery of morphology in a second language (L2) is difficult, especially for adult learners. This paper provides an overview of recent research investigating the kinds of challenges L2 learners face in acquiring and spelling out morphosyntactic features, including the extent to which L2 morphology can be successfully acquired, the extent to which morphological errors accurately reflect underlying knowledge of those features (and how we might assess this), and the role of L1 influence in ultimate attainment of the L2.

It is widely known that second language (L2) English learners misuse articles. Interestingly, recent studies (Ionin, Ko, & Wexler, 2004; Ko, Ionin, & Wexler, 2010; among others) have shown that L2 learner errors are not random but constrained by universal semantic features such as definiteness, specificity and partitivity. This study investigates how these semantic features affect Japanese speakers in their English article choice, adopting the same data collection strategy (forced elicitation task) as Ko et al. (2010). I mainly focus on partitivity effects, which have yet to be studied with L1 Japanese speakers. The results indicate that partitivity triggered errors in the Japanese speakers' article choices, which provides further evidence for the argument in the previous studies that L2 learners commit systematic errors in choosing articles as a result of their access to the semantic feature inventory in Universal Grammar. It is also, however, found that the effects of the semantic features are not equal. Specifically, the experimental data suggests the possibility that the effects of specificity might be more persistent than those of partitivity. It is then argued that over the course of the acquisition of English articles, L2 learners may go through a stage where specificity exerts stronger influence on them than partitivity, and the disparity in effect size could be attributed to the greater difficulty of determining the value of specificity on the basis of the context. That is, learners may have trouble with the valuation of specificity in some contexts while they are less likely to do so with partitivity. Consequently, L2 learners may not have received indirect negative evidence necessary to learn that specificity, unlike definiteness, plays no role in the selection of English articles.

This study reports the results of our investigation with a multiple-choice questionnaire on the interpretation of infinitive null subjects in English control and raising constructions by 30 Japanese high school students. Given that they involve two distinct syntactic derivations with two types of empty categories, the results bear on developmental acquisition pertinent to base-generation versus A-movement in L2 grammar. Interestingly, the participants did not show a strong subject-object asymmetry in the control constructions, unlike L1 children. They did show, however, a particular delay in the raising constructions, like L1 children. Based on these results, it is claimed that control constructions are not difficult for low-proficiency learners because they exist in L1 Japanese, and the participants can use their L1 knowledge together with the Extended Project Principle and the Minimal Distance Principle. However, the raising structures are not easy for Japanese learners of English because the construction on par with seem-to word order does not exist in Japanese, thereby forcing them to misapply their L1 knowledge of A-movement and observe the locality constraint. The analysis suggests that the interpretation over the experiencer is delayed due to an intervention effect relative to locality in L2 acquisition as well.