Auditory evoked potentials reveal early perceptual effects of distal prosody on speech segmentation.

Prosodic context several syllables prior (i.e., distal) to an ambiguous word boundary influences speech segmentation. To assess whether distal prosody influences early perceptual processing or later lexical competition, EEG was recorded while subjects listened to eight-syllable sequences with ambiguous word boundaries for the last four syllables (e.g., tie murder bee vs. timer derby). Pitch and duration of the first 5 syllables were manipulated to induce sequence segmentation with either a monosyllabic or disyllabic final word. Behavioral results confirmed a successful manipulation. Moreover, penultimate syllables (e.g., der) elicited a larger anterior positivity 200-500 ms after onset for prosodic contexts predicted to induce word-initial perception of these syllables. Final syllables (e.g. bee) elicited a similar anterior positivity in the context predicted to induce word-initial perception of these syllables. Additionally, these final syllables elicited a larger positive-to-negative deflection (P1-N1) 60-120 ms after onset, and a larger N400. The finding that prosodic characteristics of speech several syllables prior to ambiguous word boundaries modulate both early and late ERPs elicited by subsequent syllable onsets provides evidence that distal prosody influences early perceptual processing, and later lexical competition.