Contributions of social, contextual, and lexical factors in speech processing

This project examines the individual and combined effects of social, contextual, and lexical factors on speech processing. The results of the project are reported in: Dossey, E., Jones, Z., & Clopper, C. G. (2023). Relative contributions of social, contextual, and lexical factors in speech processing. Language and Speech, 66, 322-353. https://journals.sagepub.com/doi/10.1177/00238309221107870. This work was partially supported by the National Science Foundation (BCS-1056409)

Effects of talker and token variability on perceptual learning of dialect categories

Dialect classification is difficult for naive listeners, but perceptual learning tasks using sentence-length utterances have been shown to produce modest improvements in performance. The goal of the current study was to explore perceptual learning by naive listeners in a speeded dialect classification task with shorter, word-length utterances. In a series of experiments, participants were trained in a two-alternative forced-choice speeded dialect classification task (Cleveland vs. Cincinnati) with feedback and were then tested in the same task with novel talkers and novel words without feedback to assess learning. Variability in the stimulus materials in the training phase, including the number of talkers from each dialect and the number of different tokens produced by each talker, was manipulated across experiments to determine how variation in the input affected perceptual learning of dialect categories. The results revealed that training materials consisting of utterances produced by multiple different talkers from each dialect with multiple different tokens produced by each talker led to a significant improvement in dialect classification performance compared to a baseline condition without training. These findings suggest that dialect classification performance can improve with training on short, word-length utterances, but that robust dialect category learning requires high variability stimulus materials.7 page(s

Phonetic reduction, vowel duration, and prosodic structure

Word frequency, phonological neighborhood density, semantic predictability in context, and discourse mention have all been previously found to cause reduction of vowels. Other researchers have suggested that reduction based on these factors is reflective of a unified process in which “redundant” or “predictable” elements are reduced, and that this reduction is largely mediated by prosody. Using a large read corpus, we show that these four factors show different types of reduction effects, and that there are reduction effects of prosody independent of duration, and vice versa, suggesting the existence of multiple processes underlying reduction

Variation in /u/ fronting in the American Midwest

Previous research has suggested that a greater degree of social indexing of gender, race, and regional background is produced in linguistic contexts that promote phonetic reduction. The goal of the current study was to explore this hypothesis through an examination of the realization of an ongoing sound change in the American Midwest—/u/ fronting—as a function of four linguistic factors that contribute to phonetic reduction: lexical frequency, phonological neighborhood density, discourse mention, and speaking style. The results revealed minimal effects of the linguistic factors on the degree of /u/ fronting among talkers with greater overall advancement in the /u/ fronting change-in-progress, suggesting that the process of /u/ fronting is nearing completion among some American Midwesterners. However, the results also revealed more /u/ fronting in plain laboratory speech than in clear laboratory speech and in low-frequency, low-density words than in low-frequency, high-density words among talkers with lower overall advancement in the /u/ fronting change-in-progress. The directions of these effects are consistent with the hypothesis that social indexing is greater in reduction-promoting contexts. Further, the relative sizes of these effects suggest that speaking style contributes more to variability in social indexing than lexical properties, such as frequency and neighborhood density

Interactions among lexical and discourse characteristics in vowel production

Various factors are known to affect vowel production, including lexical frequency, neighborhood density, contextual predictability, mention in the discourse, and speaking style. This study explores interactions among all five of these factors on vowel duration and dispersion. Participants read paragraphs containing target words varying in frequency, density, and predictability. Each target word appeared twice in the paragraph. Participants read each paragraph twice: as if they were talking to a friend ( plain speech ) and as if they were talking to a hearing-impaired or non-native interlocutor ( clear speech ). Measures of vowel duration and dispersion were obtained. Results revealed that high frequency words and words in plain speech were shorter and less dispersed in the vowel space than low frequency words and words in clear speech, and that second mentions were less dispersed in the vowel space than first mentions, as expected. A series of interactions among the lexical and discourse factors was also observed for both vowel duration and vowel dispersion, suggesting maximization of phonetic reduction in some contexts that impose limited processing costs on the listener and maximization of phonetic enhancement in other contexts that impose heavy processing costs on the listener

Assessing predictability effects in connected read speech

A wide range of reduction phenomena have been described in the literature as predictability effects, in which more predictable units (i.e. words, syllables, vowels) are reduced in duration or other acoustic dimensions relative to less predictable units. The goal of the current study was to critically evaluate these predictability effects on vowel duration in read speech to explore the extent to which they reflect a single underlying phenomenon. The results revealed shorter vowel duration for words with high phonotactic probability, for high-frequency words (in clear speech only), and for words in plain lab speech relative to clear speech. However, the results also revealed qualitatively different effects of three measures of contextual probability (cloze probability, written trigram probability, and spoken trigram probability). Greater spoken trigram probability predicted longer vowel duration, contrary to expectations, and this effect was limited to high-frequency words in first mentions and in plain speech. Cloze probability and written trigram probability exhibited even more complex interactions with other predictability measures. These results provide evidence for fundamental differences in these measures of predictability, suggesting that a more nuanced perspective on predictability effects and the mechanisms underlying them is necessary to account for the complexity of the empirical data

Ohio State Stories (OSS) Corpus Data Processing

Data processing workflow, associated Praat and R scripts, and sample data files from the Ohio State Stories corpus. The corpus is available here: https://u.osu.edu/storiescorpus/. This work was partially supported by the National Science Foundation (BCS-1056409)

Children's perception of dialect variation

A speaker's regional dialect is a rich source of information about that person. Two studies examined five- to six-year-old children's perception of regional dialect: Can they perceive differences among dialects? Have they made meaningful social connections to specific dialects? Experiment 1 asked children to categorize speakers into groups based on their accent; Experiment 2 asked them to match speakers to (un)familiar cultural items. Each child was tested with two of the following: The child's Home dialect, a Regional variant of that dialect, and a Second-Language variant. Results showed that children could successfully categorize only with a Home vs. Second-Language dialect contrast, but could reliably link cultural items with either a Home vs. Second-Language or a Regional vs. Second-Language dialect contrast. These results demonstrate five- to six-year-old children's developing perceptual skill with dialect, and suggest that they have a gradient representation of dialect variation.23 page(s