A Probabilistic Model of Parallelism 1 Running head: A PROBABILISTIC MODEL OF PARALLELISM A Probabilistic Corpus-based Model of Syntactic Parallelism

Work in experimental psycholinguistics has shown that the processing of coordinate structures is facilitated when the two conjuncts share the same syntactic structure (Frazier, Munn, & Clifton, 2000). In the present paper, we argue that this parallelism effect is a specific case of the more general phenomenon of syntactic priming—the tendency to repeat recently used syntactic structures. We show that there is a significant tendency for structural repetition in corpora, and that this tendency is not limited to syntactic environments involving coordination, though it is greater in these environments. We present two different implementations of a syntactic priming mechanism in a probabilistic parsing model and test their predictions against experimental data on NP parallelism in English. Based on these results, we argue that a general purpose priming mechanism is preferred over a special mechanism limited to coordination. Finally, we show how notions of activation and decay from ACT-R can be incorporated in the model, enabling it to account for a set of experimental data on sentential parallelism in German.