Pitch variability in spontaneous speech production and its connection to usage-based grammar

This study explores pitch variability in language production and its implication for processing advantages of holistic units, with a specific focus on the relationship between disyllabic word production and their distributional properties in language use. Using a 185-million-word native corpus as a proxy for the statistical properties of native usage, the study examines how pitch variability of disyllabic words in a spontaneous speech corpus of Taiwan Mandarin is influenced by lexical frequency, predictive contingencies, and retrodictive contingencies. Building upon the duration-based pairwise variability index (PVI), this study introduces two variants of pitch-related PVI (f0PVI) to quantify pitch variability within speech segments. We assess their effectiveness through three phonetic analyses. The first analysis shows that disyllabic words exhibit significantly lower f0PVI values than their non-holistic part-word counterparts, indicating the metric's capability to distinguish holistic linguistic units. The second analysis uncovers a significant inverse correlation between the pitch variability metrics of disyllabic words and their frequency values, highlighting a strong link between reduced prosodic prominence and the frequency-based processing advantages in lexical production. Finally, the third analysis demonstrates moderated effects of retrodictive lexical contingency on pitch variability, contingent on the word's alignment with prosodic junctures. We discuss the implications of contextual predictability in lexical retrieval and its role in the dynamic planning process of speech production. Our findings underscore f0PVI as a robust prosodic measure for the automatized processing and entrenchment of linguistic units arising from repeated usage.