Doctoral Dissertation Research Improvement Grant: Structure and Plasticity of Bilingual Sound Systems

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In an era of increasing globalization and immigration, the speech heard on a daily basis is becoming less homogenous, and various accents and dialects permeate everyday activities as interactions between people from different language backgrounds increase. Speakers of different languages use different acoustic information to decide what sounds they are hearing. For example, while both English and Spanish have a sound contrast between "p" and "b," listeners pay attention to different aspects of the sound signal (or different "acoustic cues") to determine the difference between these sounds in the two languages. This means that a person listening to another language, or to foreign-accented speech, may not be paying attention to the same parts of the sound that are relevant for the speaker, which could lead to difficulties in intelligibility. For effective speech comprehension, listeners must rapidly accommodate to different accents by shifting their attention to the aspects of the sounds that are relevant for the speaker. The proposed dissertation research explores how one's native language can shape the way sound categories are produced and perceived, as well as to what extent listeners adapt when confronted with changes in these categories.The first part of the research will explore which acoustic cues are most relevant to distinguishing contrasts like "p" vs. "b" in English and Spanish. The second set of experiments will explore how the "boundaries" of these sound categories can be shifted. Perhaps the most striking example of accommodation is provided by bilinguals, who switch from using the sounds of one language to another effortlessly and instantaneously. However, monolingual listeners also shift their sound category boundaries to accommodate to new accents. The proposed research will explore the plasticity of sound categories, or the rate and magnitude at which listeners shift their category boundaries when confronted with speech that is pronounced differently than usual, as happens when hearing an unfamiliar foreign accent. The research will also investigate whether bilinguals show more plasticity than monolinguals. Together, the results of the proposed experiments will increase understanding of how sound categories are structured in different languages and which factors contribute to the plasticity of these categories, with the broader aim of providing insight into the challenges involved in understanding foreign or foreign-accented speech.