UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
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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 The Role of Age and Bilingualism on Perception of Vocoded Speech(2020) Waked, Arifi Noman; Goupell, Matthew J; Ratner, Nan; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation examines the role of age and bilingualism on perception of vocoded speech in order to determine whether bilingual individuals, children, and bilingual individuals with later ages of second language acquisition show greater difficulties in vocoded speech perception. Measures of language skill and verbal inhibition were also examined in relation to vocoded speech perception. Two studies were conducted, each of which had two participant language groups: Monolingual English speakers and bilingual Spanish-English speakers. The first study also explored the role of age at the time of testing by including both monolingual and bilingual children (8-10 years), and monolingual and bilingual adults (18+ years). As such, this study included four total groups of adult and child language pairs. Participants were tested on vocoded stimuli simulating speech as perceived through an 8-channel CI in conditions of both deep (0-mm shift) and shallow (6-mm shift) insertion of the electrode array. Between testing trials, participants were trained on the more difficult, 6-mm shift condition. The second study explored the role of age of second language acquisition in native speakers of Spanish (18+ years) first exposed to English at ages ranging from 0 to 12 years. This study also included a control group of monolingual English speakers (18+ years). This study examined perception of target lexical items presented either in isolation or at the end of sentences. Stimuli in this study were either unaltered or vocoded to simulate speech as heard through an 8-channel CI at 0-mm shift. Items presented in isolation were divided into differing levels of difficulty based on frequency and neighborhood density. Target items presented at the ends of sentences were divided into differing levels of difficulty based on the degree of semantic context provided by the sentence. No effects of age at testing or age of acquisition were found. In the first study, there was also no effect of language group. All groups improved with training and showed significant improvement between pre- and post-test speech perception scores in both conditions of shift. In the second study, all participants were significantly negatively impacted by vocoding; however, bilingual participants showed greater difficulty in perception of vocoded lexical items presented in isolation relative to their monolingual peers. This group difference was not found in sentence conditions, where all participants significantly benefited from greater semantic context. From this, we can conclude that bilingual individuals can make use of semantic context to perceive vocoded speech similarly to their monolingual peers. Neither language skills nor verbal inhibition, as measured in these studies, were found to significantly impact speech perception scores in any of the tested conditions across groups.Item AN ANALYSIS OF CODE SWITCHING EVENTS IN TYPICALLY DEVELOPING SPANISH-ENGLISH BILINGUAL CHILDREN(2020) Guevara, Sandra Stephanie; Ratner, Nan; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Code-switching (CS) patterns were investigated in language samples of 14 typically-developing Spanish-English bilingual preschool-aged children. CS occurred primarily when the children spoke in Spanish. We investigated code-switched events, vocabulary measures, and disfluencies to better understand if children utilize code-switching to fill in lexical gaps in Spanish, as measured by disfluencies surrounding the code-switch. Results indicate that children’s spoken vocabulary diversity is not related to code-switching frequency, although their receptive vocabulary skills are negatively correlated to proportions of code-switched events. We also found no significant relationship between code-switched events and disfluencies across participants. Findings suggest clinical implications related to best practice for speech-language pathologists when working with bilingual children, as they observe language attrition, and code-switching related to language proficiency and dominance.Item An Investigation of Inhibitory Control in Bilingual Aphasia(2015) Sampson, Monica; Faroqi-Shah, Yasmeen; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Speaking involves selecting words and syntactic structures from among numerous competing options. It has been suggested that constant practice in using inhibitory control (IC) to limit within and cross-language competition may be associated with better lexical-semantic IC in proficient bilingual speakers relative to monolingual speakers. This advantage is also theorized to generalize to IC advantages in non-linguistic tasks (bilingual advantage hypothesis; BAH; Bialystok, 2001). However, conflicting evidence with regard to bilingual IC advantages abound, and the nature of relationship between linguistic and domain-general inhibitory control abilities is poorly understood. Since IC is proposed to be critical for lexical retrieval, it is important to understand the nature of IC engaged in individuals with lexical retrieval deficits (aphasia). Bilingual speakers with aphasia provide an ideal platform to examine the relationship between language processing and IC because there are seemingly contradictory effects at play: while bilingualism may render an IC advantage, acquired brain injury may be associated with less efficient IC. These contrasting effects allow one to tease apart the effects of bilingualism on IC, the domain generality of the bilingual IC advantage, and relationship between bilingualism, IC and lexical selection. It is important to examine these effects relative to matched monolingual controls to understand (i) if there is a bilingual advantage in lexically based IC and, (ii) the domain generality of any bilingual IC advantage. To address these aims, IC engaged in (i) lexical retrieval (semantically blocked cyclic naming task), (ii) linguistic processing (Stroop task), and (iii) non-linguistic processing (flanker task) was compared in ten each of bilingual (Tamil-English) and monolingual (English) neurologically healthy speakers and participants with aphasia. Results from neurologically healthy participants revealed a bilingual advantage in the blocked cyclic naming task (lexical IC) but no advantages in the non-lexical Stroop and flanker tasks. Results from participants with aphasia revealed no support for the proposed bilingual advantages in all three experiments. Furthermore, there was no significant association between inhibitory control measures in the three experimental tasks for all participants. Contrary to the predictions of the BAH, the collective results of this study indicate that there is insufficient evidence for the role of bilingualism in modulating non-lexical IC advantages. This lack of consistent support for BAH questions the influence of bilingual experience in modulating non-linguistic inhibitory control. These findings also reveal that the relationship between inhibitory control and lexical retrieval is not influenced by language background (monolingual versus bilingual) in persons with aphasia.Item Executive function in aphasia: is there a bilingual advantage?(2013) Baughman, Susan; Faroqi-Shah, Yasmeen; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Previous studies have demonstrated that there is a bilingual advantage in neurotypical populations on tasks of executive functions, particularly inhibition. However, little research has been conducted on a population with aphasia. This study examined whether bilingual persons with aphasia (BPWA) and monolingual persons with aphasia (MPWA) displayed any differences on tasks of executive functions. Four BPWA and four MPWA matched for age and Western Aphasia Battery subtest scores were administered a linguistic Stroop task, a nonlinguistic Stroop task, a trail-making task, and a non-verbal memory task. Results demonstrated that the two groups did not have significantly different scores on any of the tasks. While both groups of PWA were slower than neurotypical adults on reaction time measures, accuracy on all four tasks was unimpaired and within the normal range. These results, although preliminary given the small sample size and high performance accuracy, suggest that there may not be a clear "bilingual advantage" on tasks of executive function.