UC San Diego

This dissertation presents a survey of center-embedding across languages, the factors involved in the processing difficulties, and implications for the evolution of human language.First, I discuss prior typological, experimental, and theoretical research on syntactic center-embedding, with a particular focus on how its acceptability and processability differs between SVO languages and SOV languages. The evidence shows that both universal factors and language-specific factors are involved, including clause types, referential form of subjects, and case marking. Building on this cross-linguistic survey, I present the results of a corpus study demonstrating that center-embedding is more common in verb-final languages. In addition, I examine sentences from the corpus search, and other observed English examples of multiple center-embedding, with regard to the facilitating semantic and syntactic factors observed in experiments. In addition to linguistic data, I report on experimental results including a series of nonlinguistic iterated sequence learning experiments intended to elicit the formation of center-embedding. While embedded structures did appear, they rarely showed up at more than chance rates, but there were (sometimes significant) differences between conditions. Specifically, repeated icons in initial strings did seem to prompt the formation of embedding. Additionally, I report on a pair of artificial language experiments involving dependency structures. The results suggest that center-embedding is particularly hard to process, possibly even harder than crossed dependencies (which are very rare in natural language). The results thus stand at odds with natural language typology. Next I put these findings into a broader perspective, exploring the roots of center-embedding in nonlinguistic (and not exclusively human) cognitive abilities. Based on a range of observational and experimental evidence, I argue that center-embedding is an inheritance from nonlinguistic cognition, limited in its scope in language by specific features of language (i.e. time pressure and semantics). Drawing on previous animal cognitive research, I present the results of another novel experiment, an attempt to teach birds to recognize a form of simple center-embedded pattern; one subject showed signs of successful learning. Finally I discuss the greater implications of these findings for the evolution of center-embedding in particular and language evolution in general.