This thesis explores the role of age in second language (L2) acquisition and first language (L1) attrition. The focus is on Voice Onset Time (VOT) in the production and categorical perception of word-initial L1 and L2 stops in highly advanced L1 Spanish learners of L2 Swedish. Using as the point of departure a maturational constraints perspective and the Critical Period Hypothesis (CPH), Study I examines the impact of age of onset (AO) of L2 acquisition on the production of L2 Swedish voiceless stops. The results show that there are AO effects even in the speech of highly advanced L2 learners and that the incidence of nativelike L2 learners is considerably lower than earlier assumed. However, conclusions like these are only possible when speaking rate is accounted for, thereby highlighting the importance of speaking rate effects on VOT as a measure of nativelikeness. Like Study I, Study II reveals age effects on the same L2 learners’ categorical perceptions of L2 Swedish stops. Moreover, after combining the results with the data from Study I, the incidence of nativelike behavior drops remarkably with no late L2 learner performing within the range of native-speaker production and perception. The results suggest that L2 acquisition of phonetic/phonological aspects is especially sensitive to AO effects. It is concluded that theories on maturational constraints, including the CPH, cannot be refuted on the basis of the present data. Study III concerns the same participants’ production and perception of L1 Spanish stops. Age of reduced contact (ARC) is identified as an important predictor for L1 attrition and retention of voiceless stop production, although not of stop perception. This discrepancy is related to different activation thresholds as proposed by the Activation Threshold Hypothesis (ATH). It is further suggested that early bilinguals are more dependent on high-frequency L1 use than late bilinguals when compensating for age effects, but only in production. / <p>At the time of doctoral defence the following papers were unpublished and had a status as follows: Paper 1: Accepted. Paper 2: In press. Paper 3: Manuscript.</p> / Age of onset and ultimate attainment in second language acquisition, The Bank of Sweden Tercentenary Foundation, grant no. 1999-0383:01 / First language attrition in advanced second language speakers, Swedish Research Council, grant no. 421-2004-1975

<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>

This study presents detailed phonetic and acoustic analyses of the speech characteristics of two new cases of Foreign Accent Syndrome (FAS). Participants include a 48-year-old female who began speaking with an "Eastern European" accent following a traumatic brain injury, and a 45-year-old male who presented with a "British" accent following a subcortical cerebral vascular accident (CVA). Identical samples of the participants' pre- and post-morbid speech were obtained, thus affording a new level of control in the study of Foreign Accent Syndrome. The speech tasks consisted of oral readings of the Grandfather Passage and 18 real words comprised of the stop consonants /p/, /t/, /k/, /b/, /d/, /g/ combined with the peripheral vowels /i/, /a/ and /u/ and ending in a voiceless stop. Computer-based acoustic measures included: 1) voice onset time (VOT), 2) vowel durations, 3) whole word durations, 4) first, second and third formant frequencies, and 5) fundamental frequency. Formant frequencies were measured at three points in the vowel duration: a) 20%, b) 50%, and c) 80% to assess differences in vowel 'onglides' and 'offglides'. The phonetic analysis provided perceptual identification of the major phonetic features associated with the foreign quality of participant's FAS speech, while acoustic measures allowed precise quantification of these features. Results indicated evidence of backing of consonant and vowel productions for both participants. The implications for future research and clinical applications are also considered.

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The present study is the first to examine the effect of first versus second language (L1 versus L2) speech production on specific temporal parameters of speech in bilingual speakers with neurogenic speech disorders. Three persons with apraxia of speech (AOS), three with phonemic paraphasia (PP) and five normal speaking participants were included as subjects in the study. Subjects were required to read phonemically similar L1 and L2 target utterances in a carrier phrase, five times each, at a normal and fast speaking rate, respectively. This rendered four speaking contexts that included speech production in L1 at either a normal (L1NR) or fast speaking rate (L1FR) and speech production in L2 at either a normal (L2NR) or fast speaking rate (L2FR). Acoustic analysis of on-target productions involved measurement of utterance onset duration, vowel duration, utterance duration and voice onset time. Results revealed that in normal speakers, speech production in L2 results in greater token-to-token variability than in L1. However, token-to-token variability in the experimental subjects did not tend to increase whilst speaking in L2, most probably because these subjects generally decreased their speaking rate in this context, resulting in more consistent production. The subjects with AOS and PP seemed to be influenced by the increased processing demands of speaking in L2 to a greater extent than the normal speakers, in that they more frequently experienced difficulty with durational adjustments (decreasing duration in the fast speaking rate) in L2 than in L1. Furthermore, the subjects with AOS or PP also exhibited a greater extent of durational adjustment in L1 than in L2. The durations of most of the subjects with either AOS or PP tended to differ from those of the normal group to a greater extent in L2FR that was hypothesized to be the most demanding speaking context for these subjects. The longer than normal durations and greater than normal token-to-token variability in the subjects with either AOS or PP imply the presence of a motor control deficit. The extent of the motor control deficit appears to be more severe in AOS than in PP as is evident from the finding that the subjects with AOS generally exhibited longer durations and greater token-to-token variability than the subjects with PP. The pattern of breakdown in respect of different parameters and utterance groups also differed between subjects with AOS and PP. The nature of the disorder in AOS and PP thus appears to be both quantitatively and qualitatively different. Regarding measurement of the different temporal parameters, voice onset time appears to be less subject to the influence of L2 than the other measured temporal parameters. The results of this study imply that bilingual AOS is as much a reality as bilingual aphasia. Furthermore, the results underscore the importance of taking contextual factors, specifically L1 versus L2, into account when compiling assessment and treatment procedures for persons with either AOS or PP, since speech production in L2 appears to be motorically more difficult than in L1 for persons with neurogenic involvement. The significance of the results is discussed with reference to the influence of speech production in L2 on temporal control and the underlying nature of AOS and PP with regard to theories of speech sensorimotor control. Copyright / Dissertation (DPhil (Communication Pathology))--University of Pretoria, 2004. / Speech-Language Pathology and Audiology / unrestricted

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