Hearing & Speech Sciences Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2776
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Item Evaluating the role of acoustic cues in identifying the presence of a code-switch(2024) Exton, Erika Lynn; Newman, Rochelle S.; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Code-switching (switching between languages) is a common linguistic behavior in bilingual speech directed to infants and children. In adult-directed speech (ADS), acoustic-phonetic properties of one language may transfer to the other language close to a code-switch point; for example, English stop consonants may be more Spanish-like near a switch. This acoustically-natural code-switching may be easier for bilingual listeners to comprehend than code-switching without these acoustic changes; however, it effectively results in the languages being more phonetically similar at the point of a code-switch, which could make them difficult for an unfamiliar listener to distinguish. The goal of this research was to assess the acoustic-phonetic cues to code-switching available to listeners unfamiliar with the languages by studying the perception and production of these cues. In Experiment 1 Spanish-English bilingual adults (particularly those who hear code-switching frequently), but not English monolingual adults, were sensitive to natural acoustic cues to code-switching in unfamiliar languages and could use them to identify language switches between French and Mandarin. Such cues were particularly helpful when they allowed listeners to anticipate an upcoming language switch (Experiment 2). In Experiment 3 monolingual children appeared unable to continually identify which language they were hearing. Experiment 4 provides some preliminary evidence that monolingual infants can identify a switch between French and Mandarin, though without addressing the utility of natural acoustic cues for infants. The acoustic detail of code-switched speech to infants was investigated to evaluate how acoustic properties of bilingual infant-directed speech (IDS) are impacted by the presence of and proximity to code-switching. Spanish-English bilingual women narrated wordless picture books in IDS and ADS, and the voice onset times of their English voiceless stops were analyzed in code-switching and English-only stories in each register. In ADS only, English voiceless stops that preceded an English-to-Spanish code-switch and were closer to that switch point were produced with more Spanish-like voice onset times than more distant tokens. This effect of distance to Spanish on English VOTs was not true for tokens that followed Spanish in ADS, or in either direction in IDS, suggesting that parents may avoid producing these acoustic cues when speaking to young children.Item Interactions between language experience and cognitive abilities in word learning and word recognition(2014) Morini, Giovanna; Newman, Rochelle S; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)There has been much recent interest in the finding of a "bilingual advantage". That is, bilingualism confers benefits on various non-linguistic cognitive measures, particularly executive control. Yet bilingual children often face a different situation when it comes to language: their profile often negatively diverges from that of monolinguals, potentially leading to classification as language-disordered. This, in turn, contributes to public policies that discourage bilingualism. Most studies have examined ways in which bilinguals are better or worse than monolinguals. However, it is possible that bilinguals simply approach tasks differently, or weight information sources differently. This leads to advantages in some tasks and disadvantages in others. This dissertation seeks a principled understanding of this conflict by testing the hypothesis that differences in linguistic exposure and age alter how individuals approach the problem space for learning and comprehending language. To become proficient in a language, learners must process complex acoustic information, while relying on cognition to accomplish higher thought processes like working memory and attention. Over the course of development, individuals rely on these skills to acquire an impressive vocabulary, and to recognize words even in adverse listening conditions (e.g., when speech is heard in the presence of noise). I present findings from four experiments with monolingual and bilingual adults and toddlers. In adulthood, despite showing advantages in cognitive control, bilinguals appear to be less accurate than monolinguals at identifying familiar words in the presence of white noise. However, the bilingual "disadvantage" identified during word recognition was not present when listeners were asked to acquire novel word-object relations that were trained either in noise or in quiet. Similar group differences were identified with 30-month-olds during word recognition. Bilingual children performed significantly worse than monolinguals, particularly when asked to identify words that were accompanied by white noise. Unlike the pattern shown by adults, when presented with a word-learning task, monolingual but not bilingual toddlers were able to acquire novel word-object associations. Data from this work thus suggest that age, linguistic experience, and the demands associated with the type of task all play a role in the ability of listeners to process speech in noise.