Effects of cooperating and conflicting prosody in spoken English garden path sentences: ERP evidence for the boundary deletion hypothesis.

In reading, a comma in the wrong place can cause more severe misunderstandings than the lack of a required comma. Here, we used ERPs to demonstrate that a similar effect holds for prosodic boundaries in spoken language. Participants judged the acceptability of temporarily ambiguous English "garden path" sentences whose prosodic boundaries were either in line or in conflict with the actual syntactic structure. Sentences with incongruent boundaries were accepted less than those with missing boundaries and elicited a stronger on-line brain response in ERPs (N400/P600 components). Our results support the notion that mentally deleting an overt prosodic boundary is more costly than postulating a new one and extend previous findings, suggesting an immediate role of prosody in sentence comprehension. Importantly, our study also provides new details on the profile and temporal dynamics of the closure positive shift (CPS), an ERP component assumed to reflect prosodic phrasing in speech and music in real time. We show that the CPS is reliably elicited at the onset of prosodic boundaries in English sentences and is preceded by negative components. Its early onset distinguishes the speech CPS in adults both from prosodic ERP correlates in infants and from the "music CPS" previously reported for trained musicians.

Prosody-syntax interactions in aging: event-related potentials reveal dissociations between on-line and off-line measures.

This study used ERPs to determine whether older adults use prosody in resolving early and late closure ambiguities comparably to young adults. Participants made off-line acceptability judgments on well-formed sentences or those containing prosody-syntax mismatches. Behaviorally, both groups identified mismatches, but older subjects accepted mismatches significantly more often than younger participants. ERP results demonstrate CPS components and garden-path effects (P600s) in both groups, however, older adults displayed no N400 and more anterior P600 components. The data provide the first electrophysiological evidence suggesting that older adults process and integrate prosodic information in real-time, despite off-line behavioral differences. Age-related differences in neurocognitive processing mechanisms likely contribute to this dissociation.

Event-related potentials show online influence of lexical biases on prosodic processing.

This event-related potential study examined how the human brain integrates (i) structural preferences, (ii) lexical biases, and (iii) prosodic information when listeners encounter ambiguous 'garden path' sentences. Data showed that in the absence of overt prosodic boundaries, verb-intrinsic transitivity biases influence parsing preferences (late closure) online, resulting in a larger P600 garden path effect for transitive than intransitive verbs. Surprisingly, this lexical effect was mediated by prosodic processing, a closure positive shift brain response was elicited in total absence of acoustic boundary markers for transitively biased sentences only. Our results suggest early interactive integration of hierarchically organized processes rather than purely independent effects of lexical and prosodic information. As a primacy of prosody would predict, overt speech boundaries overrode both structural preferences and transitivity biases.