Linguistics Theses and Dissertations

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Browsing Linguistics Theses and Dissertations by Author "Baese-Berk, Melissa"

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    Factors affecting the incidental formation of novel suprasegmental categories
    (University of Oregon, 2021-11-23) Wright, Jonathan; Baese-Berk, Melissa
    Humans constantly use their senses to categorize stimuli in their environment. They develop categories for stimuli when they are young and constantly add to existing categories and learn novel categories throughout their life. A key factor when learning novel sound categories is the method a person uses to acquire the novel sound categories. Different learning methodologies interact with different neural processes and mechanisms, leading to diverse learning outcomes. However, auditory learning research has only recently begun to focus on the ways that various auditory processing structures interact with different learning methodologies. This dissertation investigates the acquisition of novel tone categories using natural tokens and an incidental learning paradigm. Throughout the experiments we demonstrated that native English participants with no prior experience with the target tone categories, from 18 to 66 years old, can use an incidental learning paradigm with natural tokens to form four novel tone categories after 30 minutes of training with very high, even perfect, accuracy. These findings confirm results from previous studies that suggest that participants can effectively learn novel sound categories through incidental learning paradigms, and we extend the investigation of factors impacting incidental learning into natural speech sound categories. Across the four experiments we examined factors known to impact novel sound category acquisition. We demonstrated that high variability of tokens within trials resulted in greater learning than when the variability was spread out across trials. We also demonstrated that training on a single talker results in robust learning to novel tokens but a sharp decline when generalizing to novel talkers. By contrast, if participants are trained on multiple talkers during training, there is less learning, but there is little or no difference when generalizing learning to novel talkers. We also demonstrated that the presence of an unfamiliar vowel in the auditory stimuli did not impact the incidental formation of novel tone categories during perception only training. Further, we demonstrated that producing the tokens on each trial destroyed perceptual learning, and we presented multiple hypotheses regarding the nature of the disruption for future investigation. We also demonstrated that the presence of an unfamiliar vowel did not further disrupt perceptual learning over training with familiar segments. Thus, as a whole, this dissertation illustrated that incidental learning paradigms are an effective and efficient means for learning novel tone categories and investigating factors known to impact novel sound category acquisition.
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    Factors that affect generalization of adaptation
    (University of Oregon, 2023-03-24) Lee, Dae-yong; Baese-Berk, Melissa
    As there is a growing population of non-native speakers worldwide, facilitating communication involving native and non-native speakers has become increasingly important. While one way to help communication involving native and non-native speakers is to help non-native speakers improve proficiency in their target language, another way is to help native listeners better understand non-native speech. Specifically, while it may be initially difficult for native listeners to understand non-native speech, the listeners may become better at this skill after short training sessions (i.e., adaptation) and they may better understand novel non-native speakers (i.e., generalization). However, it is not well-understood how native listeners adapt and generalize to a novel speaker. This dissertation investigates how speaker and listener characteristics affect generalization to a novel speaker. Specifically, we examine how acoustic characteristics and talker information interact in generalization of adaptation, how accentedness of non-native speech affects generalization to a novel speaker, and how listeners’ linguistic experience affects generalization of adaptation. The results suggest that acoustic similarity between speakers may help generalization and that listeners’ reliance on talker information is down-weighted, as long as speakers that listeners are trained with and tested with have similar acoustic characteristics. Furthermore, the results show that exposure to more accented non-native speech disrupts generalization of adaptation compared to exposure to less accented non-native speech, suggesting that having exposure to non-native speakers does not always help generalization. The results also show that having extended linguistic experience with non-native speakers may disrupt generalization to a novel non-native speaker. The results of the present study have implications for how speaker- and listener-related factors affect generalization of adaptation. Specifically, we suggest that, at least in the early stages of learning, generalization of adaptation is constrained by acoustic similarity and that generalization to a non-native speaker utilizes mechanisms that are general to speech perception, rather than specific to this type of adaptation. We suggest that exposure to non-native accented speech that is too different from the speech that listeners are familiar with may disrupt generalization. Further, we suggest that the representation of non-native accents becomes less malleable with extended linguistic experience.
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    Production and Perception of Native and Non-native Speech Enhancements
    (University of Oregon, 2020-12-08) Kato, Misaki; Baese-Berk, Melissa
    One important factor that contributes to successful speech communication is an individual’s ability to speak more clearly when their listeners do not understand their speech. Though native talkers are able to implement various acoustic-phonetic speech enhancements to make their speech more understandable to their listeners (e.g., by speaking more slowly, loudly, or by articulating sounds more clearly), such goal-oriented adaptations employed by non-native talkers are much less well-understood. This dissertation investigates how talkers’ ability to implement speech enhancements is shaped by their target language experience and how these enhancements impact listeners’ perception. Specifically, we examine acoustic characteristics of speech enhancements produced by native English talkers and non-native English talkers of higher- and lower-proficiency in different contexts: in a reading task where talkers are explicitly asked to read materials clearly, as well as in a simulated communication task where listeners’ communicative needs for enhanced intelligibility are signaled implicitly in the context. We further examine perceptual consequences of speech enhancements in terms of intelligibility (whether listeners understand the speech) and other subjective evaluations of the speech, including perceived degree of comprehensibility (how easy the listeners perceive the speech is to understand). The results show that native talkers and higher-proficiency non-native talkers generally make larger acoustic modifications than lower-proficiency talkers. However, such effects of talkers' target language experience differ depending on the type of acoustic manipulations involved in the productions. Furthermore, an improvement in intelligibility does not necessarily correspond to an improvement in other subjective evaluations of the speech, suggesting that perceptual benefits resulting from speech enhancements could vary depending on how listeners are asked to evaluate the speech. The results of this dissertation highlight that talkers have the flexibility to accommodate listeners’ communicative needs in a native and non-native language, and suggest that this flexibility is shaped by the combination of talkers’ linguistic backgrounds and the focus of adaptation. Furthermore, the current work provides evidence that perceptual consequences of speech enhancements are multi-faceted, and suggest that acoustic features of speech enhancements responsible for an improvement in intelligibility may differ from those influence other types of subjective evaluations.