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<div>This thesis research was motivated by the need for increasing speech transmission rates through a phonemic-based tactile speech communication device named TAPS (TActile Phonemic Sleeve). The device consists of a 4-by-6 tactor array worn on</div><div>the forearm that delivers vibrotactile patterns corresponding to English phonemes. Three studies that proceeded this thesis evaluated a coding strategy that mapped 39 English phonemes into vibrotactile patterns. This thesis corresponds to a continuation of the project with improvements summarized in two parts. First, a design and implementation of a training framework based on theories of second language acquisition and game-based learning is developed. A role playing game named Haptos was designed to implement this framework. A pilot study using the first version of the game showed that two participants were able to master a list of 52 words within 45 minutes of game play. Second, an improved set of haptic codes was designed. The design was based on the statistics of spoken English and included an additional set of codes that abbreviate the most frequently co-occurring phonemes in duration. The new set included 39 English phonemes and 10 additional abbreviated symbols. The new codes represent a 24 to 46% increase in word presentation rates. A second version of the Haptos game was implemented to test the new 49 codes in a learning curriculum distributed over multiple days. Eight participants learned the new codes within 6 hours of training and obtained an average score of 84.44% in symbol identification tests with error rates per haptic symbol below 18%. The results demonstrate the feasibility of employing the new codes for future work where the ability to receive longer sequences of phonemes corresponding to phrases and sentences will be trained and tested.</div>

<div><b>Purpose:</b> Previous studies have shown that children with SSD speaking a language other than English produce different types of speech errors, although there is a paucity of information investigating these differences in speech sound production (e.g., Core & Scarpelli, 2015; Fabiano-Smith & Goldstein, 2010b; Fabiano-Smith & Hoffman, 2018). This study investigates the types of speech errors produced by bilingual Spanish-English and monolingual English-speaking children matched on age, receptive vocabulary, and articulation accuracy in single words.</div><div><br></div><div><b>Methods: </b>Twelve bilingual English-Spanish speaking children, ages 4;0 to 6;11, were matched to twelve monolingual English-Speaking children. Participants completed standardized and non-standardized tests of speech and language, and performance between groups and assessment measures were compared. Consonant sound productions were categorized as correct, substitution errors, omission errors, or distortion errors.</div><div><br></div><div><b>Results: </b>Bilingual Spanish-English children were significantly more likely than monolingual English children to produce omission errors, while monolingual English children were more likely to produce distortion errors. Both groups produced similar proportions of substitution errors. Bilingual children produced similar proportions of each error type in both of their languages.</div><div><br></div><div><b>Conclusion: </b>SLPs should not rely on English normative data to diagnose SSDs in monolingual and bilingual Spanish-speaking children, as they demonstrate different errors patterns from monolingual English-speakers.</div>

<p dir="ltr">Comprehensibility refers to the degree of effort that a listener requires to understand a speaker’s utterance (Derwing & Munro, 1997; Munro & Derwing, 1995; Derwing & Munro, 2005). Previous studies on L2 pronunciation have found that segmental errors could affect comprehensibility (Derwing et al., 1998; Derwing & Munro, 1997; Isaacs & Thomson, 2020; Saito et al., 2017). However, this finding only indicates a correlation between the number of segmental errors and lower comprehensibility. It is still unclear what aspects of pronunciation L2 learners need to practice in order to improve the comprehensibility of their speech. This thesis proposes that the degree of acoustic contrast may play a role in determining comprehensibility. More specifically, it investigates the relation between Mandarin speakers’ acoustic contrast between tense and lax vowels in English (i.e., [i] and [ɪ], [u] and [ʊ]) and the perceived comprehensibility of their speech.</p><p dir="ltr">A sentence production task and a comprehensibility rating task were conducted. In the sentence production task, 20 Mandarin speakers and 10 English speakers read aloud English sentences containing tense and lax vowels and were audio-recorded. The acoustic measurements of the vowels were taken in order to compare Mandarin speakers’ acoustic realization of the tense and lax vowels with English speakers’ productions. In the comprehensibility rating task, 48 English speakers transcribed the sentences recorded during the sentence production task and rated the comprehensibility of the sentences. The comprehensibility ratings were tested for correlation with the number of transcription errors, the degree of spectral and durational contrasts between vowels, and the speakers’ US residency length, in order to investigate the relation between intelligibility errors and comprehensibility, between acoustic contrast and comprehensibility, and between US residency length and comprehensibility.</p><p dir="ltr">The results of the linear-mixed effect model indicated that spectral contrast between [u] - [ʊ], but not [i] - [ɪ], was significantly reduced in Mandarin speakers’ productions compared to the English speakers, suggesting that Mandarin speakers under-differentiated the back vowel pair. A correlation test using Kendall’s <i>tau</i> indicated a significant negative correlation between number of intelligibility errors and comprehensibility, suggesting that intelligibility errors decreased comprehensibility. A correlation test using Kendall’s <i>tau</i> indicated a significant positive correlation between the degree of spectral contrast and comprehensibility rating for sentences with semantically meaningful context, suggesting that increasing the contrast between tense and lax vowels could help increase the comprehensibility of speech. Finally, a correlation test using Kendall’s <i>tau</i><i> </i>indicated no significant correlation between US residency length and comprehensibility, meaning that the relation between residency length and comprehensibility was not confirmed.</p><p dir="ltr">To sum up, acoustic contrast could be one of the contributors to speech comprehensibility. Therefore, directing English L2 learners to focus on increasing the acoustic distance between contrasting vowels could prove a fruitful strategy for improving the comprehensibility of L2 speech.</p>

One of the key features of the hypokinetic dysarthria associated with Parkinson disease is dysprosody. While there has been ample research into the global characterization of speech in Parkinson disease, little is known about how people with Parkinson disease mark lexical stress. This study aimed to determine how people with Parkinson disease modulate pitch, intensity, duration, and vowel space to differentiate between two common lexical stress patterns in English: trochees (strong-weak pattern) and iambs (weak-strong pattern), in two syllable words. Twelve participants with mild to moderate idiopathic Parkinson disease and twelve age- and sex-matched controls completed a series of speech tasks designed to elicit token words of interest in prosodically-relevant speech tasks (picture identification (in isolation and lists) and giving directions (spontaneous speech). Results revealed that people with Parkinson disease produced a higher overall pitch and a smaller vowel space as compared to controls, though most lexical marking features were not significantly different. Importantly, the elicitation task had a significant effect on most dependent measures. Although lexical stress is not significantly impacted by Parkinson disease, we recommend that future research and clinical practice focus more on the use of spontaneous speech tasks rather than isolated words or lists of words due to the differences in the marking of lexical stress in the latter tasks, making them less useful as ecologically-valid assessments of prosody in everyday communication.

<p>While pronunciation has previously been described as a neglected skill in the second language classroom, a growing body of literature has demonstrated that pronunciation training improves students’ productions (Derwing & Munro, 2005). Mispronunciations have been shown to impact comprehensibility, intelligibility, and accentedness (Derwing & Munro, 2009). As pronunciation instruction methods have begun to be the subject of empirical research, Visual Feedback (VF) has begun to emerge as a novel method for teaching pronunciation. This method has been shown to be particularly effective for teaching voice onset time (VOT), a characteristic of voiceless stop consonants (e.g., /p, t, k/). Worth noting, English and Spanish differ concerning VOT, with English employing long VOTs (30-100ms) and Spanish short VOTs (0-30ms) (Lisker & Abramson’s, 1964). Previous research has focused exclusively on employing VF for shortening VOT, although there are some compelling reasons to question whether the size and nature of the effect would be similar for lengthening VOT. The present study examines the potential effectiveness of VF as a means of lengthening the VOT of Spanish learners of English.</p> <p>The participants of the study were twenty-six students from a large Colombian university. The experiment design consisted of a pretest, three VF interventions, a posttest, and a delayed posttest. The tests were composed of two tasks, differing in their complexity: recording words in isolation and words in utterances. Stimuli consisted of English words (n= 4266) with word-initial voiceless stops (/p, t, k/). Stimuli were controlled for stress, following vowel, and word familiarity  and were measured for VOT using Praat (Boersma & Weenink, 2022).</p> <p>Results from statistical analysis coupled with a visual inspection of the data indicated that the experimental group performed similarly in the three stages of the study and that the visual feedback paradigm did not result in changes in VOT. However, some degree of variation was found among the participants concerning their average VOTs. While some participants showed an overall increase (i.e., improvement) in English VOTs for the three phonemes /p/, /t/, and /k/ over time, other participants did not. In general, most of the participants produced English-like VOTs in the pretest, constituting a degree of ceiling effects. The rate of exposure to the target language and the saliency of English are factors that could have played a role in the development of the VOT scores of the participants before the study. Therefore, the discussion focuses on both the nature of the individual variability and the theoretical implications of ceiling effects found in the current study versus the lack of ceiling effects in other studies with similar populations.</p>

<p dir="ltr">The present dissertation addresses the gap of how the three contextual variables (power, distance, and imposition) affect the use and perception of pitch range and final pitch contours in Central Peninsular Spanish polar questions. The methodological approach in this dissertation combines a production experiment in the form of a contextualized sentence-reading task (e.g., Brown et al., 2014; Henriksen, 2013) and a perception experiment using a pragmatic judgment task (e.g., Nadeu & Prieto, 2011). Both tasks systematically incorporated a set of situations that included the contextual variables of power, distance, and imposition. Thus, this dissertation provides a systematic analysis of power, distance, and imposition to investigate their influence on the use and perception of pitch range and pitch contours. To analyze pitch in the production experiment, a categorical analysis of final pitch contours (e.g., low-rising contour) and a quantitative analysis of prosodic features (i.e., pitch range and its conversion into semitones) were conducted. For the perception experiment, analyses included the comparison of linear mixed models to examine the perceived degree of politeness.</p><p dir="ltr">The findings presented in this dissertation support the Frequency Code Hypothesis in that they showed the relevance of pitch for signaling and perceiving politeness in requests in Spanish. The results from the production experiment suggested there are no effects of power, distance, and imposition on the selection of final intonational contours. Regarding the analysis of pitch range, the results from the production experiment indicated that the use of greater pitch range was associated with an increase in the social distance between the speakers. In the perception experiment, the results indicated that an increase in pitch range was directly associated with an increase in the perceived degree of politeness. Furthermore, the findings from this dissertation provided evidence for including a systematic analysis of the contextual variables of power, distance, and imposition to conduct analyses within the politeness framework instead of analyzing the formal/informal dimension in isolation The overall results of this dissertation contribute to the understanding of how suprasegmental features are employed in showing and perceivicing politeness.</p>

<p dir="ltr">Upon acquiring or learning another language, cross-linguistic influence (CLI) is an inevitable phenomenon with which a bilingual speaker lives. One key aspect of CLI is its bidirectionality, flowing between both the first (L1) and second languages (L2) mutually affecting each other. However, investigations of L1 CLI on L2 have dominated previous bilingual studies, and despite the increasing amount of research on L2 CLI on L1, the phonetic and phonological domains remain relatively underexplored. The primary goal of the present study is to expand our understanding of the underlying mechanisms governing L2 CLI on L1 phonetics and phonology.</p><p dir="ltr">The present study investigates L2 CLI on L1 phonetics and phonology by examining both the speech perception and production of L1 sound categories among two different groups of bilinguals, Korean heritage speakers (HSs, <i>n</i> = 30) and long-term immigrants (LTIs, <i>n</i> = 27) group participants in the US, in comparison to L1(Korean)-immersed (L1-i) native speakers residing in South Korea (<i>n</i> = 30). Participants completed a series of three experimental tasks: (1) a three-alternative forced-choice (3AFC) identification task, (2) an AX discrimination task, and (3) a controlled reading paradigm task.</p><p dir="ltr">Experiment 1 (3AFC task) was conducted to investigate the extent and direction of L2 CLI in perceptual cue weighting to L1 speech categories. In this task, participants listened to a Korean word in each trial, potentially differing in the word-initial stop, and decided which word they heard from a real-word Korean minimal triplet /pul/ ‘fire,’ /p^hul/ ‘grass,’ and /p^*ul/ ‘horn.’ Specifically, the word-initial stop consisted of an eight-by-eight orthogonal voice onset time (VOT)–onset f0 continuum, created through a speech resynthesis technique. Based on the similarities and differences in the use of the two acoustic parameters between Korean (either onset f0 or VOT is a primary cue) and English stops (VOT is the primary cue), bilingual participants were expected to exhibit different cue-weighting patterns, as compared to L1-i speakers. The results from the mixed-effects logistic regression model analyses indicated that while HSs were less sensitive to the Korean primary cue, onset f0, compared to L1-i speakers—suggesting assimilation to L2 in the perceptual domain—LTIs exhibited greater sensitivity to this cue, indicating dissimilation from L2. It was also found that bilingual participants’ Korean dominance significantly influenced their cue weighting in the perception of Korean stops.</p><p dir="ltr">Experiment 2 (AX discrimination task) was administered to assess participants’ perceptual accuracy for L1 stop categories and the potential impact of L1 cue weighting, as estimated in Experiment 1, on their discrimination performance. Notably, the VOT in the stop stimuli used in the AX task were resynthesized to have a consistent VOT of 70 ms across all stimuli. This setup created a condition where participants had no choice but to rely solely on the onset f0 cue—the primary cue to the Korean lenis-aspirated stop contrast, rendering VOT, the primary cue for the voicing contrast in English stops, uninformative. The results from mixed-effects logistic regression models showed that HSs were significantly less accurate in discriminating their L1 stop categories without the VOT cue, while LTIs outperformed the L1-i speakers. That is, the LTI group, the most balanced group in terms of language dominance, had the highest accuracy in discriminating L1 contrasts among the participant groups. Furthermore, individual sensitivity to the onset f0 cue was found to be positively correlated with discrimination performance.</p><p dir="ltr">Experiment 3 (Controlled reading paradigm) aimed to examine L2 CLI on the implementation of acoustic parameters for L1 Korean stops, as well as the potential impact of proficiency and dominance on these parameters. Participants read aloud a list of minimal triplet stimuli differing in the word-initial stop within a carrier phrase. A machine-learning-based audio signal detection system was used to analyze the acoustic parameters, and Bayesian mixed-effects linear regression models, along with quadratic polynomial regression models, were implemented for statistical analysis of the processed data. The results of the production task mirrored the perception task (Experiment 1): HSs demonstrated assimilation to L2 via onset f0, while LTIs showed dissimilation, as compared to L1-i speakers. The analysis also revealed that the degree of bilingual balance in dominance and proficiency significantly influenced the implementation of onset f0, with more balanced bilinguals exhibiting greater category contrasts than less balanced bilinguals, regardless of whether they were Korean-dominant or English-dominant.</p><p dir="ltr">The findings from these experiments provide concrete evidence of L2 CLI in L1 phonetics and phonology. Importantly, the results demonstrate that not only the timing of L2 acquisition and the quantity and quality of L2 input but also the quality and quantity of L1 acquisition and bilingual balance contribute to the direction and the degree of L2 CLI in L1 speech. These findings align with the predictions of the revised Speech Learning Model (SLM-r, Flege & Bohn, 2021) and expand its scope of application to include both HSs and LTIs. In particular, the evidence of category assimilation and dissimilation lends support to the bidirectional CLI hypothesis proposed by SLM-r. To conclude, the present dissertation expands our understanding of the nature of L2 CLI in L1 phonetics and phonology in bilingual speakers.</p>

<p>A great deal of the research on cross-linguistic phonetic influence demonstrates that a speaker’s knowledge of their first language (L1) significantly affects their ability to perceive and produce sounds in any other language. While current studies show that cross-linguistic transfer occurs at the L3 level, some research suggests that properties of both L1 and L2 are present in the production of L3 (Ionin, Montrul & Santos, 2011). Many studies have addressed perception, production and factors that influence foreign speech in Second Language Acquisition (SLA) (Watkins, Rauber & Baptista, 2009). As the number of multilingual individuals rises, so does the need for studies that investigate not only SLA but also that of additional languages (i.e., Third Language Acquisition). This dissertation examines how cross-linguistic influence (CLI) occurs among English, Spanish, and Brazilian Portuguese (BP), examining instances of vowel reduction, an aspect of phonological production. English and BP are assumed as vowel reducing languages, whereas Spanish displays negligible vowel reduction in comparison. The vowel productions in L3 BP of two multilingual groups, L1English-L2Spanish-L3BP (ESP) and L1 Spanish-L2 English-BP (SEP) were investigated in two tasks: a paragraph reading task (PRT) and a carrier phrase task (CPT). The study sought to determine whether i) a native speaker of a vowel reducing L1 and a non-vowel reducing L2 displays more or less vowel reduction in a vowel reducing L3 than a native speaker of a non-vowel reducing L1 and vowel reducing L2 and ii) how length of exposure to an L3 affects phonological production. Three fixed effects were considered: duration ratio, intensity ratio and height (F1). The goal was to ascertain whether the Typological Primacy Model (TPM) (Rothman 2011, 2015) or the L2 Status Factor Model (Bardel & Falk 2007, 2012; Hammarberg, 2001) would be a better predictor for how vowel reduction would occur in the L3. Results for duration ratio and vowel height showed no significant difference between groups ESP and SEP. Results for intensity ratio suggest L2 Status as a better predictor, as group SEP displayed more phonological transfer than the ESP group. A hybrid approach to L3 acquisition models is proposed. </p>