The interaction of pitch and timing in the perception of prosodic grouping
Brugos, Alejna Mari
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Speakers break their otherwise continuous speech stream into meaningful segments, the edges of which are marked by audible cues such as pauses, rate changes and pitch movement. Prosodic boundaries, as these segment edges and the cues marking them are known, play a role critical to language processing and spoken language acquisition. While great progress has been made in quantifying the complicated range of acoustic cues that mark boundaries, little is understood about the cognitive processes by which these cues guide linguistic interpretation. Further, while prosodic boundary measures typically treat critical cues from pitch and timing independently, evidence suggests that pitch and timing are perceptually interdependent. In fact, pitch factors may at times distort perceived duration. This dissertation presents 3 pairs of perception experiments investigating pitch-time interaction, including putative distortion of perceived duration from dynamic pitch and cross-‑silence pitch jumps (i.e., the kappa effect). Each pair uses the same set of stimuli, resynthesized with crossed continua of pitch and timing manipulations, in two different tasks: one psychoacoustic judgment of duration, and one of linguistic interpretation. Results suggest that perceptual interaction of major cues from timing (preboundary lengthening and pauses) and pitch (edge tones and reset) can be analyzed as reflecting gestalt-like grouping principles (proximity, similarity and continuity) that have been shown to play a role in perceptual grouping in other cognitive domains, including vision and non-speech auditory perception. In addition to these potentially more cognitive‐general principles, a new role is introduced for learned and potentially language-specific patterns to prosodic grouping, in particular intonational schemas, i.e., recognizable cross-phrase pitch patterns. Beyond this, results also support the hypothesis that perceived grouping is the driving force behind several types of pitchbased auditory illusions, including the auditory kappa effect. This dissertation offers insights into why prosodic boundaries are expressed with the particular pitch and timing cues that are common cross-linguistically. While much language form is arbitrary, the expression of grouping by way of acoustic cues appears to be much less so. This research has potential toexplain the perceptual foundations of boundary cues, and therefore the cross-linguistic similarities of prosodic grouping cues.