L2 speech learning of European Portuguese /l/ and /ɾ/ by L1-Mandarin learners: experimental evidence and theoretical modelling

It has been long recognized that the poor distinction between /l/ and /ɾ/ is one of the most perceptible characteristics in Chinese-accented Portuguese. Recent empirical research revealed that this notorious L2 speech learning difficulty goes beyond the confusion between two L2 categories, as L1-Mandarin learners’ acquisition of Portuguese /l/ and /ɾ/ seems to be subject to the interaction among different prosodic positions, speech modalities and representational levels. This thesis aims to deepen our current understanding of this L2 speech learning process, by exploring what constrains the development of L2 phonological categories across syllable positions and how different modalities interact during this process. To achieve this goal, both experimental tasks and theoretical modelling were employed. The first study of this thesis explores the role of cross-linguistic influence and orthography on L2 category formation. In order to elicit cross-linguistic influence directly, a delayed-imitation task was performed with L1-Mandarin naïve listeners. This task examined how the Mandarin phonology parses the Portuguese input ([l], [ɾ]) in intervocalic onset and in word-internal coda position. Moreover, whether orthography plays a role during the construction of L2 phonological representation was tested by manipulating the input types that were given in the experiment (auditory input alone vs. auditory + written input). Our study shows that naïve Mandarin listeners’ responses corroborated with that of L1-Mandarin learners, suggesting that cross-linguistic influence is responsible for the observed L2 prosodic effects. Moreover, the Mandarin [ɻ] (a repair strategy for /ɾ/) occurred almost exclusively when the written form was given, providing evidence for the cross-linguistic interaction between phonological categorization and orthography during the construction of L2 categories. In the second study, we first investigate the interaction between speech perception and production in L2 speech learning, by examining whether the L2 deviant productions stem from misperception and whether the order of acquisition in L2 speech perception mirrors that in production. Secondly, we test whether L2 phonological categories remain malleable at a mid-late stage of L2 speech learning. Two perceptual experiments were performed to test L1-Mandarin learners on their discrimination ability between the target Portuguese form and the deviant form employed in L2 production. Expanding on prior research, in this study, the perceptual motivation for L2 speech difficulties was assessed in different syllable constituents (onset and coda) and at both segmental and suprasegmental levels (structural modification). The results demonstrate that some deviant forms observed in L2 production indeed have a perceptual motivation ([w] for the velarised lateral; [l] and [ɾə] for the tap), while some others cannot be attributed to misperception (deletion of syllable-final tap). Furthermore, learners confused the intervocalic /l/ and /ɾ/ bidirectionally in perception, while in production they never misproduced the lateral (/ɾ/ → [l], */l/ → [ɾ]), revealing a mismatch between two speech modalities. By contrast, the order of acquisition (/ɾ/coda > /ɾ/onset) was shown to be consistent in L2 perception and production. The correspondence and discrepancy between the two speech modalities signal a complex relationship between L2 speech perception and production. To assess the plasticity of L2 categories /l/ and /ɾ/, two groups of L1-Mandarin learners who differ substantially in terms of L2 experience were recruited in the perceptual tasks. Our study shows that both groups behaved similarly in terms of the discrimination performance. No evidence for a role of L2 experience was found. The implication of this null result on L2 phonological development is discussed. The third study of the thesis aims to contribute to bridging the gap between the L2 experimental evidence and formal theories. Adopting the Bidirectional Phonology and Phonetics Model, we formalise some of the experimental findings that cannot be elucidated by current L2 speech theories, namely, the between and within-subject variation in L2 phonological categorization; the interaction between phonological categorization and orthography during L2 category construction; and the asymmetry between L2 perception and production. Overall, this thesis sheds light on the complex nature of L2 phonological acquisition and provides a formal account of how different modalities interact in shaping L2 speech learning. Moreover, it puts forward testable predictions for future research and suggestions for improving foreign language teaching/training methodologies.É bem conhecido o facto de as trocas associadas a /l/ e /ɾ/ constituírem uma das caraterísticas mais percetíveis no português articulado pelos aprendentes chineses. Recentemente, estudos empíricos revelam que a dificuldade por parte dos aprendentes chineses não se restringe à discriminação moderada entre as duas categorias da L2, dado que a aquisição de /l/ e /ɾ/ do português por aprendentes chineses parece estar sujeita à interação entre contextos prosódicos, entre modalidades de fala e entre níveis representacionais diferentes. Esta tese visa aprofundar a nossa compreensão deste processo da aquisição fonológica L2, explorando o que condiciona o desenvolvimento das categorias fonológicas L2 em diferentes constituintes silábicos e de que modo as modalidades interagem durante este processo, recorrendo para tal a tarefas experimentais bem como a formalização teórica. O primeiro estudo averigua o papel da influência interlinguística e o da ortografia na construção das categorias de L2. Para elicitar a influência interlinguística diretamente, uma tarefa de imitação retardada foi aplicada aos falantes nativos do mandarim sem conhecimento de português, investigando assim como a fonologia do mandarim categoriza o input do português ([l], [ɾ]) em ataque simples intervocálico e em coda medial. Para além disso, a influência ortográfica na construção de representações fonológicas em L2 foi examinada através da manipulação do tipo do input apresentado na experiência (input auditivo vs. input auditivo + ortográfico). Os resultados da situação experimental em que os participantes receberam input de ambos os tipos replicaram o efeito prosódico observado na literatura, evidenciando a interação entre categorização fonológica e ortografia na construção das categorias de L2. No segundo estudo, investigamos a interação entre a perceção e a produção de fala na aquisição das líquidas do PE por aprendentes chineses e a plasticidade destas categorias fonológicas, respondendo às questões seguintes: 1) as produções desviantes de L2 resultam da perceção incorreta? 2) a ordem da aquisição em L2 é consistente na perceção e na produção? 3) as categorias da L2 permanecem maleáveis numa fase intermédia da aquisição? Duas tarefas percetivas foram conduzidas para testar a capacidade percetiva dos aprendentes nativos do mandarim em relação à discriminação entre a forma alvo do português e as formas desviantes utilizadas na produção. No presente estudo, a motivação percetiva das dificuldades em L2 foi testada nos constituintes silábicos diferentes (ataque simples e coda) e nos níveis segmental e suprassegmental (modificação estrutural). Os resultados demonstram que algumas formas desviantes que os aprendentes chineses produzem têm uma motivação percetiva (i.e. [w] para a lateral velarizada; [l] e [ɾə] para a vibrante alveolar), enquanto outras não podem ser analisadas como casos de perceção incorreta (como é o caso do o apagamento da vibrante em coda). Para além disso, na posição intervocálica, os aprendentes manifestam dificuldade na discriminação entre /l/ e /ɾ/ de forma bidirecional, mas, na produção, a lateral nunca é produzida incorretamente (/ɾ/ → [l], */l/ → [ɾ]). Tal revela uma divergência entre as duas modalidades de fala. Por contraste, mostrou-se que a ordem da aquisição (/ɾ/coda > /ɾ/ataque) é consistente na perceção e na produção da L2. A correspondência e a discrepância entre as duas modalidades de fala, sinalizam uma relação complexa entre a perceção e a produção na aquisição fonológica de L2. Em relação à questão da plasticidade das categorias de L2, recrutaram-se para as tarefas percetivas dois grupos de aprendentes nativos do mandarim que se diferenciavam substancialmente em termos da experiência em L2. Não se encontrou um efeito significativo da experiência da L2. A implicação deste resultado nulo no desenvolvimento fonológico de L2 foi discutida. O terceiro estudo desta tese tem como objetivo contribuir para a colmatação das lacunas entre estudos empíricos de L2 e as teorias formais. Adotando o Modelo Bidirecional de Fonologia e Fonética, formalizamos os resultados experimentais que as teorias atuais da aquisição fonológica de L2 não conseguem explicar, nomeadamente, a variação inter e intra-sujeitos na categorização fonológica em L2; a interação entre categorização fonológica e ortografia na construção das categorias na L2; a assimetria entre a perceção e a produção na L2. Em suma, esta tese contribui com dados empíricos para a discussão da relação complexa entre a perceção, produção e ortografia na aquisição fonológica de L2 e formaliza a interação entre essas modalidades através de um modelo linguístico generativo. Além disso, apresentam-se predições testáveis para investigação futura e sugestões para o aperfeiçoamento das metodologias de ensino/treino da língua não materna

Mechanism of extreme phonetic reduction: evidence from Taiwan Mandarin

Extreme reduction refers to the phenomenon where intervocalic consonants are so severely reduced that two or more adjacent syllables appear to be merged into one. Such severe reduction is often considered a characteristic of natural speech and to be closely related to factors including lexical frequency, information load, social context and speaking style. This thesis takes a novel approach to investigating this phenomenon by testing the time pressure account of phonetic reduction, according to which time pressure is the direct cause of extreme reduction. The investigation was done with data from Taiwan Mandarin, a language where extreme reduction (referred to as contraction) has been reported to frequently occur. Three studies were conducted to test the main hypothesis. In Study 1, native Taiwan Mandarin speakers produced sentences containing nonsense disyllabic words with varying phonetic structures at differing speech rates. Spectral analysis showed that extreme reduction occurred frequently in nonsense words produced under high time pressure. In Study 2a, further examination of formant peak velocity as a function of formant movement amplitude in experimental data suggested that articulatory effort was not decreased during reduction, but in fact likely to be increased. Study 2b examined high frequency words from three spontaneous speech corpora for reduction variations. Results demonstrate that patterns of reduction in high frequency words in spontaneous speech (Study 2b) were similar to those in nonsense words spoken under experimental conditions (Study 2a). Study 3 investigated tonal reduction with varying tonal contexts and found that tonal reduction can also be explained in terms of time pressure. Analysis of F0 trajectories demonstrates that speakers attempt to reach the original underlying tonal targets even in the case of extreme reduction and that there was no weakening of articulatory effort despite the severe reduction. To further test the main hypothesis, two computational modelling experiments were conducted. The first applied the quantitative Target Approximation model (qTA) for tone and intonation and the second applied the Functional Linear Model (FLM). Results showed that severely reduced F0 trajectories in tone dyads can be regenerated to a high accuracy by qTA using generalized canonical tonal targets with only the syllable duration modified. Additionally, it was shown that using FLM and adjusting duration alone can give a fairly good representation of contracted F0 trajectory shapes. In summary, results suggest that target undershoot under time pressure is likely to be the direct mechanism of extreme reduction, and factors that have been commonly associated with reduction in previous research very likely have an impact on duration, which in turn determines the degree of target attainment through the time pressure mechanism

Economy of Effort or Maximum Rate of Information? Exploring Basic Principles of Articulatory Dynamics

Economy of effort, a popular notion in contemporary speech research, predicts that dynamic extremes such as the maximum speed of articulatory movement are avoided as much as possible and that approaching the dynamic extremes is necessary only when there is a need to enhance linguistic contrast, as in the case of stress or clear speech. Empirical data, however, do not always support these predictions. In the present study, we considered an alternative principle: maximum rate of information, which assumes that speech dynamics are ultimately driven by the pressure to transmit information as quickly and accurately as possible. For empirical data, we asked speakers of American English to produce repetitive syllable sequences such as wawawawawa as fast as possible by imitating recordings of the same sequences that had been artificially accelerated and to produce meaningful sentences containing the same syllables at normal and fast speaking rates. Analysis of formant trajectories shows that dynamic extremes in meaningful speech sometimes even exceeded those in the nonsense syllable sequences but that this happened more often in unstressed syllables than in stressed syllables. We then used a target approximation model based on a mass-spring system of varying orders to simulate the formant kinematics. The results show that the kind of formant kinematics found in the present study and in previous studies can only be generated by a dynamical system operating with maximal muscular force under strong time pressure and that the dynamics of this operation may hold the solution to the long-standing enigma of greater stiffness in unstressed than in stressed syllables. We conclude, therefore, that maximum rate of information can coherently explain both current and previous empirical data and could therefore be a fundamental principle of motor control in speech production