Every difference between languages is a “choice point” for the syntactician, psycholinguist, and language learner. The syntactician must describe the differences in representations that the grammars of different languages can assign. The psycholinguist must describe how the comprehension mechanisms search the space of the representations permitted by a grammar to quickly and effortlessly understand sentences in real time. The language learner must determine which representations are permitted in her grammar on the basis of her primary linguistic evidence. These investigations are largely pursued independently, and on the basis of qualitatively different data. In this dissertation, I show that these investigations can be pursued in a way that is mutually informative. Specifically, I show how learnability con- cerns and sentence processing data can constrain the space of possible analyses of language differences.

In Chapter 2, I argue that “indirect learning”, or abstract, cross-contruction syntactic inference, is necessary in order to explain how the learner determines which complementizers can co-occur with subjects gaps in her target grammar. I

show that adult speakers largely converge in the robustness of the that-trace effect, a constraint on complementation complementizers and subject gaps observed in lan- guages like English, but unobserved in languages like Spanish or Italian. I show that realistic child-directed speech has very few long-distance subject extractions in En- glish, Spanish, and Italian, implying that learners must be able to distinguish these different hypotheses on the basis of other data. This is more consistent with more conservative approaches to these phenomena (Rizzi, 1982), which do not rely on ab- stract complementizer agreement like later analyses (Rizzi, 2006; Rizzi & Shlonsky, 2007).

In Chapter 3, I show that resumptive pronoun dependencies inside islands in English are constructed in a non-active fashion, which contrasts with recent findings in Hebrew (Keshev & Meltzer-Asscher, ms). I propose that an expedient explanation of these facts is to suppose that resumptive pronouns in English are ungrammat- ical repair devices (Sells, 1984), whereas resumptive pronouns in island contexts are grammatical in Hebrew. This implies that learners must infer which analysis is appropriate for their grammars on the basis of some evidence in linguistic envi- ronment. However, a corpus study reveals that resumptive pronouns in islands are exceedingly rare in both languages, implying that this difference must be indirectly learned. I argue that theories of resumptive dependencies which analyze resump- tive pronouns as incidences of the same abstract construction (e.g., Hayon 1973; Chomsky 1977) license this indirect learning, as long as resumptive dependencies in English are treated as ungrammatical repair mechanisms.

In Chapter 4, I compare active dependency formation processes in Japanese

and Bangla. These findings suggest that filler-gap dependencies are preferentially resolved with the first position available. In Japanese, this is the most deeply em- bedded clause, since embedded clauses always precede the embedding verb(Aoshima et al., 2004; Yoshida, 2006; Omaki et al., 2014). Bangla allows a within-language comparison of the relationship between active dependency formation processes and word order, since embedded clauses may precede or follow the embedding verb (Bayer, 1996). However, the results from three experiments in Bangla are mixed, suggesting a weaker preference for a lineary local resolution of filler-gap dependen- cies, unlike in Japanese. I propose a number of possible explanations for these facts, and discuss how differences in processing profiles may be accounted for in a variety of ways.

In Chapter 5, I conclude the dissertation.