Introduction 1
0.1 Motivation 1
0.2 Rationale and research orientation of the present study 3
0.3 Overture to the present study 12
0.4 Outline of the dissertation 14
PART Ⅰ LITERATURE REVIEW 15
Chapter 1 Task-based L2 Lexical Learning 17
1.1 Introduction 17
1.2 Definition of keyterms 17
1.2.1 Lexicalunit 17
1.2.1.1 Word 18
1.2.1.2 Word family 20
1.2.1.3 Lexicalunit 22
1.2.2 L2 lexical learning 25
1.2.2.1 What to learn 25
1.2.2.2 How to learn 30
1.2.3 Tasks for L2 lexical learning 32
1.2.3.1 Definition of'task'in SLA 33
1.2.3.2 Main features of tasks in SLA 34
1.3 Effects of task type on L2 lexical learning 37
1.3.1 L2 lexical learning via reading tasks 37
1.3.2 L2 lexical learning via listening tasks 38
1.3.3 L2 lexical learning via speaking tasks 41
1.3.4 L2 lexical learning via writing tasks 43
1.4 Effects of task frequency on L2 lexical learning 46
1.5 Effects of textual,lexical and learner factors on L2 lexical learning 48
1.6 Summary 50
Chapter 2 Controversies over Incidental and Intentional L2 Lexical Learning 52
2.1 Introduction 52
2.2 Traditional dichotomy between incidental and intentional L2 lexical learning 52
2.3 Arguments for incidental lexical learning and empirical findings 53
2.3.1 Default argument 54
2.3.2 Empirical evidence 55
2.4 Arguments for intentional L2 lexical learning and empirical findings 58
2.4.1 Pedagogical advocacy 58
2.4.2 Empirical evidence 59
2.5 Unsettled issues 63
2.5.1 Theoretical problems 63
2.5.2 Methodological problems 64
2.6 Solutions in the present study 67
2.7 Summary 71
Chapter 3 Controversies over Involvement Load Hypothesis 72
3.1 Introduction 72
3.2 Involvement Load Hypothesis 72
3.2.1 Theoretical base 73
3.2.2 Construct of task-induced involvement 75
3.2.3 Assumptions of the Involvement Load Hypothesis 78
3.3 Empirical findings 79
3.4 Controversial issues 85
3.5 Solutions in the present study 89
3.6 General fram ework of the present study 90
3.7 Summary 94
PART Ⅱ METHODOLOGY 97
Chapter 4 Research Design 99
4.1 Introduction 99
4.2 Thepilot study 99
4.2.1 Research Questions 99
4.2.2 Subjects 100
4.2.3 Materials 101
4.2.3.1 Design of the treatment text 101
4.2.3.2 Target LUs and their basic features 103
4.2.4 Tasks 106
4.2.5 Instruments and procedures 108
4.2.6 Data collection 112
4.2.7 Data analysis 114
4.2.8 Major findings 115
4.2.8.1 Effects of task type 115
4.2.8.2 Effects of task frequency 117
4.2.8.3 Effects of lexical presentation 120
4.2.9 Limitations 121
4.2.10 Solutions in the main study 124
4.3 Themain study 124
4.3.1 Research questions 125
4.3.2 Research design 126
4.3.3 Subjects 127
4.3.4 Material 132
4.3.4.1 Revised treatment text 132
4.3.4.2 Target LUs and their basic features 134
4.3.5 Tasks 135
4.3.6 Instruments 135
4.3.7 Procedures 141
4.3.8 Data collection 143
4.3.9 Data analysis 146
4.3.9.1 Quantitative analysis 146
4.3.9.2 Qualitative analysis 151
4.4 Summary 152
PART Ⅲ RESULTS AND DISCUSSIONS 155
Chapter 5 Effects of Task Type 157
5.1 Introduction 157
5.2 Overall effects of task type 157
5.3 Modified effects of task type 161
5.3.1 Correlation between learning outcomes and English proficiency 161
5.3.2 Effects of task type modified by English proficiency 164
5.4 Role of task-induced involvement load 175
5.4.1 Task-based construct of task involvement 175
5.4.1.1 Invalidation of motivational-cognitive construct of task involvement 177
5.4.1.2 Validation of task-basked construct of task involvement 181
5.4.2 Differentia tedroles of receptive and productive tasks 186
5.4.3 Involvement Load Hypothesis 188
5.4.4 Tasks with optimal involvement 191
5.4.4.1 Tasks with optimal facilitative powers 192
5.4.4.2 Components and constraints of optimal involvement 193
5.5 Summary 207
Chapter 6 Effects of Task Frequency 210
6.1 Introduction 210
6.2 Overall effects of task frequency 210
6.2.1 Effects of task frequency on the 4 EGs'lexical learning 211
6.2.2 Effects of task frequency on each EG's lexical learning 213
6.2.2.1 Task frequency on each EG's ultimate learning outcomes 213
6.2.2.2 Task frequency on each EG's netlexical gains 216
6.2.2.3 Interaction between task frequency and task type 219
6.3 Modified effects of task frequency 224
6.3.1 Effects of task frequency on HL subgroups'lexical learning 229
6.3.2 Effects of task frequency on ML subgroups'lexical learning 232
6.3.3 Effects of task frequency on LL subgroups'lexical learning 238
6.4 Optimal task frequency 245
6.4.1 Overall optimal task frequency 245
6.4.2 Variations in the optimal task frequency 254
6.5 Summary 259
Chapter 7 Effects of Lexical Presentation 261
7.1 Introduction 261
7.2 Effects of lexical formation 261
7.2.1 Overall effects of lexical formation 262
7.2.2 Variations in the effects of lexical formation on eachtype of the target LUs 264
7.3 Effects of contextual elaborations 268
7.3.1 Overall effects of contextual elaborations 268
7.3.2 Variations in the effects of contextual elaborations 275
7.4 Most and least learned target LUs 280
7.5 Summary 292
PART Ⅳ CONCLUSION 295
Chapter 8 Findings,Implications and Limitations 297
8.1 Major findings 297
8.1.1 Findings related to the effects of task type on L2 lexical learning. 297
8.1.2 Findings related to the effects of task frequency on L2 lexical learning 299
8.1.3 Findings related to lexical presentation in L2 lexical learning 301
8.1.4 Findings related to the effects of English proficiency on L2 lexical learning 303
8.2 Contributions 303
8.2.1 Theoretical contributions 303
8.2.1.1 Modifying the motivational-cognitive construct of task-induced involvement and the Involvement Load Hypothesis 304
8.2.1.2 Clarifying the role of input and output in task-based L2 lexical learning 307
8.2.1.3 Revealing the complexity of task-based L2 lexical learning 308
8.2.2 Pedagogical contributions 310
8.2.2.1 Applying the effects of task type to L2 lexical teaching 310
8.2.2.2 Applying the effects of task frequency to L2 lexical teaching 311
8.2.2.3 Applying the effects of word and text factors to L2 lexical teaching 313
8.2.2.4 Applying vocabulary acquisition tests to L2 lexical teaching 314
8.2.3 Methodological contributions 315
8.2.3.1 Implementing the experimental design with care 315
8.2.3.2 Combining the quantitative and qualitative methods to explore L2 lexical learning 317
8.2.3.3 Devising more valid scoring of VKS tomeasure incremental L2 lexical learning 318
8.3 Limitations 319
8.3.1 Methodo logica lissues 319
8.3.2 Genera lizability issues 320
8.4 Suggestions for future research 321
8.5 Summary 323
Appendix Ⅰ Treatment Text for the Pilot Study 325
Appendix Ⅱ A Spelling Test of Target Lexical Units 327
Appendix Ⅲ Guided Writing 329
Appendix Ⅳ Vocabulary Acquisition Test of the Pilot Study 331
Appendix Ⅴ A Sentence Translation Exercise 337
Appendix Ⅵ The 7-scale Scoring of VKS for the Pilot Study 339
Appendix Ⅶ Revised Vocabulary Acquisition Test for the Main Study 340
Appendix Ⅷ Interview Guide 345
References 348