Implicit learning as a mechanism for syntactic acquisition and processing: Evidence from syntactic priming.

Abstract

Learning to decode and communicate meaning from how words are combined is a challenge that children must meet in order to acquire the syntax of their language. The mechanisms of this process are hotly debated: do children have innate linguistic knowledge guiding their learning or are their innate abilities limited to learning mechanisms that infer knowledge from input? Syntactic priming offers an experimental paradigm that can test different theories of syntactic acquisition. Presenting a prime sentence of a particular syntactic structure (e.g., the passive: the swimmer was eaten by a crocodile) tends to increase the likelihood of participants later producing that structure over an alternative (e.g., the cyclist was swooped by the magpie vs the active: the magpie swooped the cyclist). A syntactic priming effect implies shared representation between the prime and target, illuminating the nature of the underlying syntactic representation. In addition, syntactic priming may be a short-term manifestation of a proposed mechanism of syntactic acquisition and processing: implicit error-based learning. The aim of this thesis was to investigate the contribution that research using syntactic priming can make to our understanding of mechanisms of syntactic acquisition and processing. The first part of this thesis focuses on acquisition. It reports the first longitudinal study of syntactic priming in children aged 3;0 - 4;6 years, tracking the development of priming with and without shared lexical content between primes and participants' responses (e.g., both being swooping events). The developmental trajectories of abstract and lexically-dependent knowledge are key to differentiating between theories of syntactic acquisition. Abstract priming emerged early and decreased across development once the target structure had been acquired, while lexically-specific priming emerged later and increased over development. This pattern is most consistent with an implicit error-based learning account rather than lexicalist accounts where initial syntactic representations are tied to lexical items, or purely nativist accounts where priming effects are expected to be stable, like the representations they tap into. The second study in Part 1 of this thesis synthesised the existing syntactic priming literature. A meta-analysis of syntactic priming studies in children showed that the priming effect is robust and reliable. The structural alternation under investigation and aspects of study design were identified as influences on the syntactic priming effect that researchers should consider. A key finding was that priming was larger with, but not dependent on, shared lexical content between primes and participants' responses, supporting the findings of the longitudinal study. The second part of this thesis explored combining syntactic priming with pupillometry, a real-time psychophysiological measure. The implicit error-based learning account proposes a cognitive architecture that is continuous from children to adults, linking syntactic acquisition in children to syntax processing in adults. It posits that prediction error leads to representational change. Pupil size provided a potential index of prediction error, allowing exploration of the mechanistic link between unexpected syntactic structure and representational change as measured via priming. Overall, this thesis applies three lenses to syntactic priming - longitudinal research, meta-analysis, and online psychophysiological measurement - to extend the utility of the methodology, the conclusions we can draw from it and the depth of evidence for an implicit error-based learning account of syntax processing and acquisition.