Poster F72, Tuesday, March 28, 8:00 – 10:00 am, Pacific Concourse
Neural Consequences of Syntactic Surprisal during Reading
Trevor Brothers1, Matthew W. Lowder1, John M. Henderson1, Fernanda Ferreira1, Matthew J. Traxler1, Tamara Y. Swaab1; 1University of California, Davis
While it is clear that readers can use semantic context to generate predictions for upcoming words, much less is known about abstract, syntactic predictions generated at the level of word categories. In the current study, we used a computational modelling approach, in which the syntactic expectedness (or surprisal) of each word in a text is calculated using a probabilistic incremental parser. By correlating these syntactic surprisal values with ongoing EEG, we can estimate when readers are first sensitive to subtle violations of syntactic expectation within natural (error-free) text. Twenty participants read short, two-sentence narratives for comprehension while EEG was recorded from the scalp. The syntactic surprisal of each word was calculated using a probabilistic context-free grammar (Roarke, et al., 2009), and this measure of syntactic difficulty was used to predict brain responses following word onset. In this analysis we also controlled for nine additional contextual and lexical variables known to influence neural responses during reading. Syntactic surprisal did not modulate the amplitude of the N400. Instead, words high in syntactic surprisal generated a late positivity (500-700ms) over frontal electrode sites. The topography of this syntactic surprisal effect was distinct from posterior “P600 effects”, triggered by syntactic anomalies. This result suggests that readers are sensitive to subtle differences in syntactic predictability within natural texts, and that syntactic surprisal and syntactic violations may produce dissociable brain responses (Kaan & Swaab, 2003). We will discuss the potential relationship between syntactic surprisal effects and other late frontal positivities linked to violations of semantic expectancies.
Topic Area: LANGUAGE: Syntax