PREFACE LIST OF TABLES LIST OF FIGURES LIST OF ABBREVIATIONS CHAPTER 1 INTRODUCTION 1.1 Background of the Study 1.2 Aims of the Study 1.3 Research Questions and Hypotheses 1.4 Structure of the Study CHAPTER 2 LITERATURE REVIEW 2.1 Vocabulary Learning 2.1.1 Word and Three Dimensions 2.1.2 Receptive and Productive Vocabulary Knowledge 2.1.3 Intentional and Incidental Vocabulary Learning 2.2 Previous Studies on L2 Incidental Vocabulary Learning 2.2.1 Incidental Vocabulary Learning through Written Input 2.2.2 Incidental Vocabulary Learning through Audio-visual Input 2.3 Theoretical Framework for Audio-visual Input 2.3.1 Comprehensible Input 2.3.2 The Dual-Coding Theory 2.4 Incidental Vocabulary Learning and Factors 2.4.1 Learners' Pre-existing Vocabulary Knowledge 2.4.2 Frequency of Occurrence 2.4.3 Text Comprehension 2.4.4 Contextual Clues 2.4.5 Motivation 2.4.6 Part of Speech 2.4.7 Word Frequency in Corpus CHAPTER 3 METHODOLOGY 3.1 Statement for the Methodology 3.2 Participants 3.3 Group Design 3.4 Materials 3.5 Target Words 3.6 Testing Instruments 3.6.1 Target��word Test 3.6.2 Vocabulary Knowledge Test 3.6.3 Comprehension Test 3.6.4 Vocabulary Size Test 3.6.5 Questionnaire 3.7 Treatment Procedures 3.8 Scoring 3.9 Ethic Code for the Study CHAPTER 4 DATA ANALYSES AND RESULTS 4.1 Effcts of TED-talk Videos and Written Input 4.1.1 Findings from Form Recognition Tests 4.1.2 Findings from Meaning Recall Tests 4.1.3 Findings from Production Tests 4.2 E��cts of Embedded On.screen L2 Captions 4.2.1 Findings from Form Recognition Tests 4.2.2 Findings from Meaning Recall Tests 4.2.3 Findings from Production Tests 4.3 Effects of Repeated TED-talk Viewing 4.3.1 Findings from Form Recognition Tests 4.3.2 Findings from Meaning RecaU Tests 4.3.3 Findings from Production Tests 4.4 Effectsof Learuer_related Factors 4.4.1 Leamers��Pre-existing Vocabulary Knowledge 4.4.2 Text Comprehension Proficiency 4.4.3 Other Learner.related Factors 4.4.4 IJeamers'V0cabulary Improvement 4.4.5 correlation between Learner-related Factors and Vocabublory Improvement 4.5 Effects of Item-related Factors CHAPTER 5 DISCUSSION 5.1 Effectsof TED-talk Videos and Written Input 5.2 Effects of Embedded 0n-screen L2 Captions 5.3 Effeets 0f Repeated TED-talk Viewing 5.4 Effects of Learner-related Factors 5.5 Effects of Item.related Factors CHAPTER 6 CONCLUSION 6.1 Summary of the Findings 6.2 Pedagogical Implications 6.3 Limitations and Suggest!ons for Further Studies REFERENCES POSTSCRIPT