We show that the pupillometry method, which continuously captures minute changes in pupil size, provides a natural, real-time measure sensitive to mismatches between prosodic and syntactic group- ing. Pupillometry is increasingly used as a measure of language comprehension, finding increased pupil size for syntactically complex sentences (e.g., Engelhardt et al., 2010), violations of expected meter (Scheepers et al., 2013), and inadequate or misleading pitch accent (Zellin et al., 2011).
Using materials from Kjelgaard & Speer (1999), we found that improper prosodic boundary location in- creases pupil size, which increased differentially when the syntactic structure was independently hard to parse. The findings suggest that prosodic mis-alignment created additional cognitive load during auditory sentence comprehension, confirming that prosodic boundaries are immediately incorporated into structural analysis. We discuss implications for theories of prosody-syntax alignment in real-time sentence parsing, along with methodological and statistical innovations afforded by this method.