Self-imitating Feedback Generation Using GAN for Computer-Assisted Pronunciation Training

Self-imitating feedback is an effective and learner-friendly method for non-native learners in Computer-Assisted Pronunciation Training. Acoustic characteristics in native utterances are extracted and transplanted onto learner's own speech input, and given back to the learner as a corrective feedback. Previous works focused on speech conversion using prosodic transplantation techniques based on PSOLA algorithm. Motivated by the visual differences found in spectrograms of native and non-native speeches, we investigated applying GAN to generate self-imitating feedback by utilizing generator's ability through adversarial training. Because this mapping is highly under-constrained, we also adopt cycle consistency loss to encourage the output to preserve the global structure, which is shared by native and non-native utterances. Trained on 97,200 spectrogram images of short utterances produced by native and non-native speakers of Korean, the generator is able to successfully transform the non-native spectrogram input to a spectrogram with properties of self-imitating feedback. Furthermore, the transformed spectrogram shows segmental corrections that cannot be obtained by prosodic transplantation. Perceptual test comparing the self-imitating and correcting abilities of our method with the baseline PSOLA method shows that the generative approach with cycle consistency loss is promising

CAPT를 위한 발음 변이 분석 및 CycleGAN 기반 피드백 생성

학위논문(박사)--서울대학교 대학원 :인문대학 협동과정 인지과학전공,2020. 2. 정민화.Despite the growing popularity in learning Korean as a foreign language and the rapid development in language learning applications, the existing computer-assisted pronunciation training (CAPT) systems in Korean do not utilize linguistic characteristics of non-native Korean speech. Pronunciation variations in non-native speech are far more diverse than those observed in native speech, which may pose a difficulty in combining such knowledge in an automatic system. Moreover, most of the existing methods rely on feature extraction results from signal processing, prosodic analysis, and natural language processing techniques. Such methods entail limitations since they necessarily depend on finding the right features for the task and the extraction accuracies. This thesis presents a new approach for corrective feedback generation in a CAPT system, in which pronunciation variation patterns and linguistic correlates with accentedness are analyzed and combined with a deep neural network approach, so that feature engineering efforts are minimized while maintaining the linguistically important factors for the corrective feedback generation task. Investigations on non-native Korean speech characteristics in contrast with those of native speakers, and their correlation with accentedness judgement show that both segmental and prosodic variations are important factors in a Korean CAPT system. The present thesis argues that the feedback generation task can be interpreted as a style transfer problem, and proposes to evaluate the idea using generative adversarial network. A corrective feedback generation model is trained on 65,100 read utterances by 217 non-native speakers of 27 mother tongue backgrounds. The features are automatically learnt in an unsupervised way in an auxiliary classifier CycleGAN setting, in which the generator learns to map a foreign accented speech to native speech distributions. In order to inject linguistic knowledge into the network, an auxiliary classifier is trained so that the feedback also identifies the linguistic error types that were defined in the first half of the thesis. The proposed approach generates a corrected version the speech using the learners own voice, outperforming the conventional Pitch-Synchronous Overlap-and-Add method.외국어로서의 한국어 교육에 대한 관심이 고조되어 한국어 학습자의 수가 크게 증가하고 있으며, 음성언어처리 기술을 적용한 컴퓨터 기반 발음 교육(Computer-Assisted Pronunciation Training; CAPT) 어플리케이션에 대한 연구 또한 적극적으로 이루어지고 있다. 그럼에도 불구하고 현존하는 한국어 말하기 교육 시스템은 외국인의 한국어에 대한 언어학적 특징을 충분히 활용하지 않고 있으며, 최신 언어처리 기술 또한 적용되지 않고 있는 실정이다. 가능한 원인으로써는 외국인 발화 한국어 현상에 대한 분석이 충분하게 이루어지지 않았다는 점, 그리고 관련 연구가 있어도 이를 자동화된 시스템에 반영하기에는 고도화된 연구가 필요하다는 점이 있다. 뿐만 아니라 CAPT 기술 전반적으로는 신호처리, 운율 분석, 자연어처리 기법과 같은 특징 추출에 의존하고 있어서 적합한 특징을 찾고 이를 정확하게 추출하는 데에 많은 시간과 노력이 필요한 실정이다. 이는 최신 딥러닝 기반 언어처리 기술을 활용함으로써 이 과정 또한 발전의 여지가 많다는 바를 시사한다. 따라서 본 연구는 먼저 CAPT 시스템 개발에 있어 발음 변이 양상과 언어학적 상관관계를 분석하였다. 외국인 화자들의 낭독체 변이 양상과 한국어 원어민 화자들의 낭독체 변이 양상을 대조하고 주요한 변이를 확인한 후, 상관관계 분석을 통하여 의사소통에 영향을 미치는 중요도를 파악하였다. 그 결과, 종성 삭제와 3중 대립의 혼동, 초분절 관련 오류가 발생할 경우 피드백 생성에 우선적으로 반영하는 것이 필요하다는 것이 확인되었다. 교정된 피드백을 자동으로 생성하는 것은 CAPT 시스템의 중요한 과제 중 하나이다. 본 연구는 이 과제가 발화의 스타일 변화의 문제로 해석이 가능하다고 보았으며, 생성적 적대 신경망 (Cycle-consistent Generative Adversarial Network; CycleGAN) 구조에서 모델링하는 것을 제안하였다. GAN 네트워크의 생성모델은 비원어민 발화의 분포와 원어민 발화 분포의 매핑을 학습하며, Cycle consistency 손실함수를 사용함으로써 발화간 전반적인 구조를 유지함과 동시에 과도한 교정을 방지하였다. 별도의 특징 추출 과정이 없이 필요한 특징들이 CycleGAN 프레임워크에서 무감독 방법으로 스스로 학습되는 방법으로, 언어 확장이 용이한 방법이다. 언어학적 분석에서 드러난 주요한 변이들 간의 우선순위는 Auxiliary Classifier CycleGAN 구조에서 모델링하는 것을 제안하였다. 이 방법은 기존의 CycleGAN에 지식을 접목시켜 피드백 음성을 생성함과 동시에 해당 피드백이 어떤 유형의 오류인지 분류하는 문제를 수행한다. 이는 도메인 지식이 교정 피드백 생성 단계까지 유지되고 통제가 가능하다는 장점이 있다는 데에 그 의의가 있다. 본 연구에서 제안한 방법을 평가하기 위해서 27개의 모국어를 갖는 217명의 유의미 어휘 발화 65,100개로 피드백 자동 생성 모델을 훈련하고, 개선 여부 및 정도에 대한 지각 평가를 수행하였다. 제안된 방법을 사용하였을 때 학습자 본인의 목소리를 유지한 채 교정된 발음으로 변환하는 것이 가능하며, 전통적인 방법인 음높이 동기식 중첩가산 (Pitch-Synchronous Overlap-and-Add) 알고리즘을 사용하는 방법에 비해 상대 개선률 16.67%이 확인되었다.Chapter 1. Introduction 1 1.1. Motivation 1 1.1.1. An Overview of CAPT Systems 3 1.1.2. Survey of existing Korean CAPT Systems 5 1.2. Problem Statement 7 1.3. Thesis Structure 7 Chapter 2. Pronunciation Analysis of Korean Produced by Chinese 9 2.1. Comparison between Korean and Chinese 11 2.1.1. Phonetic and Syllable Structure Comparisons 11 2.1.2. Phonological Comparisons 14 2.2. Related Works 16 2.3. Proposed Analysis Method 19 2.3.1. Corpus 19 2.3.2. Transcribers and Agreement Rates 22 2.4. Salient Pronunciation Variations 22 2.4.1. Segmental Variation Patterns 22 2.4.1.1. Discussions 25 2.4.2. Phonological Variation Patterns 26 2.4.1.2. Discussions 27 2.5. Summary 29 Chapter 3. Correlation Analysis of Pronunciation Variations and Human Evaluation 30 3.1. Related Works 31 3.1.1. Criteria used in L2 Speech 31 3.1.2. Criteria used in L2 Korean Speech 32 3.2. Proposed Human Evaluation Method 36 3.2.1. Reading Prompt Design 36 3.2.2. Evaluation Criteria Design 37 3.2.3. Raters and Agreement Rates 40 3.3. Linguistic Factors Affecting L2 Korean Accentedness 41 3.3.1. Pearsons Correlation Analysis 41 3.3.2. Discussions 42 3.3.3. Implications for Automatic Feedback Generation 44 3.4. Summary 45 Chapter 4. Corrective Feedback Generation for CAPT 46 4.1. Related Works 46 4.1.1. Prosody Transplantation 47 4.1.2. Recent Speech Conversion Methods 49 4.1.3. Evaluation of Corrective Feedback 50 4.2. Proposed Method: Corrective Feedback as a Style Transfer 51 4.2.1. Speech Analysis at Spectral Domain 53 4.2.2. Self-imitative Learning 55 4.2.3. An Analogy: CAPT System and GAN Architecture 57 4.3. Generative Adversarial Networks 59 4.3.1. Conditional GAN 61 4.3.2. CycleGAN 62 4.4. Experiment 63 4.4.1. Corpus 64 4.4.2. Baseline Implementation 65 4.4.3. Adversarial Training Implementation 65 4.4.4. Spectrogram-to-Spectrogram Training 66 4.5. Results and Evaluation 69 4.5.1. Spectrogram Generation Results 69 4.5.2. Perceptual Evaluation 70 4.5.3. Discussions 72 4.6. Summary 74 Chapter 5. Integration of Linguistic Knowledge in an Auxiliary Classifier CycleGAN for Feedback Generation 75 5.1. Linguistic Class Selection 75 5.2. Auxiliary Classifier CycleGAN Design 77 5.3. Experiment and Results 80 5.3.1. Corpus 80 5.3.2. Feature Annotations 81 5.3.3. Experiment Setup 81 5.3.4. Results 82 5.4. Summary 84 Chapter 6. Conclusion 86 6.1. Thesis Results 86 6.2. Thesis Contributions 88 6.3. Recommendations for Future Work 89 Bibliography 91 Appendix 107 Abstract in Korean 117 Acknowledgments 120Docto

More is more in language learning:reconsidering the less-is-more hypothesis

The Less-is-More hypothesis was proposed to explain age-of-acquisition effects in first language (L1) acquisition and second language (L2) attainment. We scrutinize different renditions of the hypothesis by examining how learning outcomes are affected by (1) limited cognitive capacity, (2) reduced interference resulting from less prior knowledge, and (3) simplified language input. While there is little-to-no evidence of benefits of limited cognitive capacity, there is ample support for a More-is-More account linking enhanced capacity with better L1- and L2-learning outcomes, and reduced capacity with childhood language disorders. Instead, reduced prior knowledge (relative to adults) may afford children with greater flexibility in inductive inference; this contradicts the idea that children benefit from a more constrained hypothesis space. Finally, studies of childdirected speech (CDS) confirm benefits from less complex input at early stages, but also emphasize how greater lexical and syntactic complexity of the input confers benefits in L1-attainment

Nonword Repetition and Interactions Among Vocabulary, Phonotactic probability, and Phonological Awareness in Four Linguistic Groups

The current study was designed to compare the English nonword repetition accuracy in 7-year-old monolingual English, Korean–English bilingual, Chinese–English bilingual, and Spanish–English bilingual children. The relationships among nonword repetition accuracy, vocabulary, phonological awareness, and phonotactic probability in each group of children were also examined. The results indicated significant differences among the groups’ accuracy of consonants and vowels by syllable length. Different correlational patterns emerged among nonword repetition accuracy, vocabulary, and phonological awareness. Theoretical and clinical implications for the use of nonword repetition tasks for children from various linguistic backgrounds are discussed

Focusing on Rater Variability and Phonetic Correlates

학위논문(박사) -- 서울대학교대학원 : 사범대학 외국어교육과(영어전공), 2022. 8. 안현기.유창성은 제2언어 수행과 언어능력에서 매우 중요한 부분을 구성하고 있으며, 많은 제2언어 학습자가 유창성을 획득하고자 노력하고 있다. 그러나 제2언어 연구자나 EFL(외국어로서의 영어) 교육자들은 유창성에 대해 명확히 이해하지 못하고 있으며, 그 개념 또한 일관성 있게 정의하지 못하고 있다. 게다가 EFL 환경에서 다양한 평가자들이 어떻게 유창성을 인식하고 평가하는지에 대한 연구는 매우 부족하다. 이러한 학문적인 필요성을 충족하고, 유창성의 다차원적 구성에 대한 깊은 이해를 위해 본 연구는 원어민 교사, 비원어민 교사, 그리고 동료 학생들이 한국 고등학생의 영어 말하기 유창성을 어떻게 인식하고 평가하는지를 인식 유창성과 발화 유창성이라는 두 가지 관점에서 연구하였다. 연구 1은 혼합 연구 방법을 이용하여 세 평가 집단의 인식 유창성이 어떻게 다른지를 비교한 것이다. 세 집단의 평가자는 다른 말하기 능력(상, 중, 하)을 가진 발화자가 두 과제 유형(그림 이야기, 자유 발화)에 대해 수행한 샘플을 듣고 유창성을 평가하였고, 연구자는 세 집단의 전반적인 유창성 점수는 양적인 방법으로, 채점자의 서면 평가는 질적인 방법으로 분석하였다. 두 과제와 세 언어 능력 집단 모두에게서 원어민과 비원어민 교사 집단은 비슷한 수준의 엄격성 패턴을 보였지만 동료 학생 집단은 교사 집단에 비해 유의미하게 낮은 점수를 주었음이 드러났다. 이어진 질적 분석은 EFL 교사 집단과 동료 학생 집단의 차이를 다시 한번 확인시켜주었다. 그리고 세 평가 집단이 하 수준의 학생들을 평가할 때, 그림 이야기에는 낮은 점수를 준 반면 자유 발화에는 높은 점수를 주는 경향을 보여, 모든 평가 집단이 과제 유형에 상당한 영향을 받음이 드러났다. 연구 1에서 발견된 세 그룹의 유창성 인식의 차이는 연구 2에서 좀 더 뒷받침된다. 연구 2에서는 발화 유창성의 특성 중 어떤 요소나 어떤 음향 모델이 평가자들의 인식 유창성을 가장 잘 예측할 수 있는지, 또한 어떤 발화 유창성 특성이 평가자로 하여금 발화자의 유창성 수준을 판단하는 데 영향을 미치는지를 알아보기 위해 발화 유창성과 인식 유창성 간의 관계를 분석하였다. 그 결과 두 가지 속도와 관련된 특질(평균 발화 길이, 발화 속도)과 휴지와 관련된 특질(절 내 무음 휴지기 비율, 평균 무음 휴지 길이)이 세 평가 집단의 인식 유창성과 가장 큰 상관이 있는 것으로 나타났다. 회귀 분석 결과 평균 발화 길이와 평균 무음 휴지 길이가 회귀 모형의 가장 많은 변화량을 설명하며 세 평가 집단의 유창성 점수를 가장 잘 예측하는 것으로 드러났다. 하지만 원어민과 비원어민 교사 집단의 모델은 입력 변수와 변수의 상대적인 순위 측면에서 완전히 동일한 반면 동료 학생 집단의 회귀 모형은 교사 집단의 모형과 차이가 있음이 발견되었다. 그리고 무음 휴지의 평균 길이와 같은 휴지와 관련된 특질은 하 수준의 유창성을 가진 학생을 구분하는 데 사용되고, 발화 속도와 같은 속도 관련 특질은 상 수준의 유창성을 가진 학생을 구분하는 데 사용되고 있음이 밝혀졌다. 이러한 연구 결과들은 원어민 교사와 비교하여 유창성 평가자로서 비원어민 교사들의 역할에 대한 논의에 바탕이 되었고, 동료 학생 평가의 타당성과 신뢰성을 논의하는 토대를 만들었다. 연구 1과 연구 2에서 드러난 여러 실증적인 증거들을 바탕으로 원어민과 비원어민 교사는 모두 제2언어로서 영어 말하기 유창성을 비슷한 방식으로 인식하고 평가하는 것으로 결론 지을 수 있고, 비원어민 교사 평가자도 원어민 교사 평가자와 같이 유창성 평가에 동일한 평가자로 기능할 수 있음을 보여주었다. 하지만 동료 학생 집단은 교사 집단에 비해 다른 평가 양상을 보여주었고, 이는 이들이 한국의 EFL 환경에서 능숙한 유창성 평가자로서의 역할을 수행하기 위해서는 많은 교육적인 노력이 필요함을 시사한다. 현 논문은 다양한 평가 집단이 학생들의 영어 말하기 유창성을 어떻게 인식하고 평가하는지를 체계적으로 분석하며, 한국 EFL 환경에서 타당하고 신뢰성이 있는 유창성 평가 방식을 수립하는데 기여한다. 게다가 본 연구는 동료 학생들의 평가를 교사 집단의 평가와 비교하여 연구함으로서 동료 평가의 가능성과 한계에 대한 직접적인 증거를 제시하였다. 또한 연구 방법론과 관련하여 본 연구는 유창성의 두 가지 측면인 인식 유창성과 발화 유창성을 결합함으로서 유창성의 다차원적 구성을 이해하는데 도움을 주고, 양적인 방법론과 질적인 방법론을 결합하여 다양한 평가 집단의 평가 패턴을 종합적으로 이해하는데 기여한다.Fluency constitutes a crucial aspect of understanding second language (L2) performance and proficiency, and attaining high levels of fluency is one essential goal for many L2 learners. However, fluency has not been well understood, and the term has not been used consistently by L2 researchers and EFL educators. In addition, there is a paucity of studies concerning how raters in the EFL context perceive and evaluate fluency. To fill the academic gap and deepen understanding of the multidimensional construct of fluency, the current dissertation investigated how Korean English teachers, native English teachers, and peer students perceive and rate Korean high school students' speaking fluency in terms of perceived fluency and utterance fluency. Study 1 investigated the differences in perceived fluency by three rater groups, employing a mix-method approach. Overall fluency ratings across two task types (picture narration, spontaneous speech) at speakers' different oral proficiency levels (low, mid, high) were analyzed quantitatively, and raters' written comments were examined qualitatively. The native and non-native teacher groups showed comparable severity patterns, but the peer group provided significantly lower fluency rating scores than the two EFL teacher groups on both tasks across all proficiency levels. The following qualitative analyses confirmed the discrepancy between the two EFL teacher groups and the peer group. In addition, it was revealed that the three rater groups' evaluations for low-level learners were significantly affected by task types, with the spontaneous speech task scoring higher than the picture narration task. The disparities in the three groups' perceptions of fluency reported in Study 1 were further supported and accounted for in Study 2. Study 2 examined the relationship between utterance fluency and perceived fluency to determine which acoustic model best predicted the three listener groups' perceived fluency and which acoustic features were associated with the three groups' decision-making of speakers' fluency levels. Two speed features (i.e., mean length of run, articulation rate) and two breakdown measures (i.e., silent pause rate within a clause, mean length of silent pauses) were found to be most strongly correlated with their perceived fluency. The regression analysis indicated that the mean length of run and the mean length of silent pauses were the two strongest predictors for the three rater groups, explaining most of the variance in the three regression models. However, the data further revealed that the regression models for native and non-native teachers were identical regarding the four entered variables and their relative contribution rankings, while the best regression model for the peer group showed some disparities. In addition, it was found that breakdown measures, such as the mean length of silent pauses, helped to distinguish the low-level from higher level (mid, high) groups, while speed measures, such as articulation rate, discriminated the high-level group from lower level (low, mid) groups. These findings served as a foundation for a discussion of native versus non-native English teachers as fluency assessors on the one hand and the validity and reliability of peer assessment on the other. Based on empirical evidence drawn from Study 1 and 2, it can be concluded that native and non-native English teachers perceived and rated L2 fluency in a similar way, confirming that non-native teachers are as equally capable of serving as fluency raters as native teachers are. However, the peer group displayed rating patterns distinct from those of the teacher group, implying that much pedagogical effort is required to prepare peer students to serve as competent fluency raters in the Korean EFL context. The current dissertation contributes to establishing a valid and reliable fluency assessment in the Korean EFL context by systematically analyzing how various groups of raters perceive and evaluate students' English speaking fluency. In addition, the study provides direct evidence regarding the possibility and limitations of peer assessment by comparing the peer group's judgments with those of the teacher groups. Regarding research methodology, the study contributes to illuminating the multidimensional constructs of fluency by combining two facets of fluency, like perceived fluency and utterance fluency. It is also shown that a comprehensive understanding of rating patterns drawn by different raters can be achieved by combining quantitative and qualitative research methods.CHAPTER 1. INTRODUCTION 1 1.1 Aims of Study 1 1.2 Background of Study 2 1.3 Research Questions 7 1.4 Organization of the Dissertation 9 CHAPTER 2. LITERATURE REVIEW 11 2.1 Defining and Measuring Fluency 11 2.2 Perceived Fluency 18 2.2.1 Rater Variables on Fluency Ratings 18 2.2.2 Task Variables on Fluency Ratings 26 2.3 Utterance Fluency 30 2.3.1 Predictors of Utterance Fluency 30 2.3.1.1 Speed Fluency 31 2.3.1.2 Breakdown Fluency 34 2.3.1.3 Repair Fluency 39 2.3.2 Utterance Fluency Model 42 2.3.3 Utterance Fluency Features and Fluency levels 46 CHAPTER 3. Study 1: PERCEIVED FLUENCY 49 3.1 Methodology 49 3.1.1 Participants 50 3.1.2 Instruments 53 3.1.3 Procedures 55 3.1.4 Data Analysis 57 3.2 Results 59 3.2.1 A Quantitative Study 59 3.2.1.1 Comparison of the Three Rater Groups 59 3.2.1.2 Effects of Raters and Task Types on Fluency Ratings 64 3.2.2 A Qualitative Study 73 3.3 Summary and Discussion 87 CHAPTER 4. Study 2: UTTERANCE FLUENCY 96 4.1 Methodology 96 4.1.1 Participants and Procedures 97 4.1.2 Temporal Measures 98 4.1.3 Acoustic Analysis 101 4.1.4 Statistical Analysis 103 4.2 Results 106 4.2.1 Predictors of Three Rater Groups’ Fluency Ratings 106 4.2.2 A Best Prediction Model on L2 Speaking Fluency 113 4.2.3 Utterance Measures Distinguishing Fluency Levels 119 4.3 Summary and Discussion 125 CHAPTER 5. CONCLUSION 134 5.1 Findings and Pedagogical Implications 134 5.2 Limitations and Suggestions for Future Research 143 REFERENCES 145 APPENDICES 155 ABSTRACT IN KOREAN 163박

THE RELATIONSHIP BETWEEN ACOUSTIC FEATURES OF SECOND LANGUAGE SPEECH AND LISTENER EVALUATION OF SPEECH QUALITY

Second language (L2) speech is typically less fluent than native speech, and differs from it phonetically. While the speech of some L2 English speakers seems to be easily understood by native listeners despite the presence of a foreign accent, other L2 speech seems to be more demanding, such that listeners must expend considerable effort in order to understand it. One reason for this increased difficulty may simply be the speaker’s pronunciation accuracy or phonetic intelligibility. If a L2 speaker’s pronunciations of English sounds differ sufficiently from the sounds that native listeners expect, these differences may force native listeners to work much harder to understand the divergent speech patterns. However, L2 speakers also tend to differ from native ones in terms of fluency – the degree to which a speaker is able to produce appropriately structured phrases without unnecessary pauses, self-corrections or restarts. Previous studies have shown that measures of fluency are strongly predictive of listeners’ subjective ratings of the acceptability of L2 speech: Less fluent speech is consistently considered less acceptable (Ginther, Dimova, & Yang, 2010). However, since less fluent speakers tend also to have less accurate pronunciations, it is unclear whether or how these factors might interact to influence the amount of effort listeners exert to understand L2 speech, nor is it clear how listening effort might relate to perceived quality or acceptability of speech. In this dissertation, two experiments were designed to investigate these questions

Comparing the outcomes of early and late acquisition of european portuguese: an analysis of morpho-syntactic and phonetic performance

The present paper compares the linguistic competence of German-Portuguese bilinguals with upper-intermediate German L2 learners (L2ers) of EP (European Portuguese) and with monolingual Portuguese speakers. The bilingual speakers are heritage speakers (HSs), who were raised bilingually with EP as the minority language and German as the majority language. The aim of our comparison is to verify in which way different input sources and maturational effects shape the speakers’ linguistic knowledge. The findings of two studies, one focused on the morpho-syntactic knowledge of clitics and the other on global accent, corroborate the assumption that L2ers and HSs behave differently, despite superficial similarities observed in the morpho-syntactic study. In contrast to that of the L2ers’, the accent of the HSs is perceived as being native-like, whereas their morpho-syntactic competence is mainly shaped by their dominant exposure to colloquial Portuguese and reduced contact with formal registers.info:eu-repo/semantics/publishedVersio

The phonetics of second language learning and bilingualism

This chapter provides an overview of major theories and findings in the field of second language (L2) phonetics and phonology. Four main conceptual frameworks are discussed and compared: the Perceptual Assimilation Model-L2, the Native Language Magnet Theory, the Automatic Selection Perception Model, and the Speech Learning Model. These frameworks differ in terms of their empirical focus, including the type of learner (e.g., beginner vs. advanced) and target modality (e.g., perception vs. production), and in terms of their theoretical assumptions, such as the basic unit or window of analysis that is relevant (e.g., articulatory gestures, position-specific allophones). Despite the divergences among these theories, three recurring themes emerge from the literature reviewed. First, the learning of a target L2 structure (segment, prosodic pattern, etc.) is influenced by phonetic and/or phonological similarity to structures in the native language (L1). In particular, L1-L2 similarity exists at multiple levels and does not necessarily benefit L2 outcomes. Second, the role played by certain factors, such as acoustic phonetic similarity between close L1 and L2 sounds, changes over the course of learning, such that advanced learners may differ from novice learners with respect to the effect of a specific variable on observed L2 behavior. Third, the connection between L2 perception and production (insofar as the two are hypothesized to be linked) differs significantly from the perception-production links observed in L1 acquisition. In service of elucidating the predictive differences among these theories, this contribution discusses studies that have investigated L2 perception and/or production primarily at a segmental level. In addition to summarizing the areas in which there is broad consensus, the chapter points out a number of questions which remain a source of debate in the field today.https://drive.google.com/open?id=1uHX9K99Bl31vMZNRWL-YmU7O2p1tG2wHhttps://drive.google.com/open?id=1uHX9K99Bl31vMZNRWL-YmU7O2p1tG2wHhttps://drive.google.com/open?id=1uHX9K99Bl31vMZNRWL-YmU7O2p1tG2wHAccepted manuscriptAccepted manuscrip

Factors Influencing Intelligibility and Comprehensibility: A Critical Review of Research on Second Language English Speakers

The varieties of English have led to the paradigm of Global Englishes, which describes the ideologies of English as a lingua franca (ELF) and World Englishes (differential uses of English internationally) in diverse sociolinguistic contexts. Global Englishes literature complicates intelligibility and comprehensibility since it tends to problematize “native norms” as the only benchmarks for successful lingua franca use. Intelligibility and comprehensibility studies have recently been concerned with the interaction between non-native speakers using English as a second language for communication. Thus, this paper critically evaluates research on intelligibility and comprehensibility of second language (L2) English speakers. It is observed that various speaker, listener, and contextual factors may affect intelligibility and comprehensibility. Based on the influencing factors, this paper also makes several recommendations for how intelligibility and comprehensibility can be improved. It is suggested that further research is needed for L2 instruction that may be promising for improving intelligibility and comprehensibility