Introduction 1
①Research Background 1
②Statement of the Problem 3
③Purpose of the Study 4
④Conceptual Framework 5
⑤Organization of the Dissertation 7
Chapter One Literature Review 9
Introduction 9
1.1 Online Language Learning 9
1.1.1 Online Education 9
1.1.2 Research Status of Online Language Learning 11
1.1.3 Foreign Language Learning 13
1.2 Benefits of Online Education 14
1.2.1 Organizational Framework of Online Learning Community 14
1.2.2 Sense of Community 15
1.3 Learners'Continuance Intention Toward Online Education 17
1.3.1 TAM 17
1.3.2 ECM 28
1.4 Interaction in Distance Education 32
1.4.1 Definition 32
1.4.2 Instructional Interaction 35
1.4.3 System Interactivity 36
1.5 Equivalence Theory 40
1.5.1 Online Interactions with Learners 40
1.5.2 Equivalence Theory 42
1.6 Interaction Hypothesis（IH） 44
1.6.1 Versions of IH 44
1.6.2 Deficiencies of IH 45
1.7 Socio-cultural Theory 46
1.7.1 ZPD 47
1.7.2 Mediation 50
1.7.3 Language.as a Symbolic Tool for Mediation 51
1.8 Scaffolding 52
1.8.1 Metaphor and Definition 52
1.8.2 Features and Functions of Scaffolding 55
1.8.3 Design of Scaffolding in Online Education 57
Summary 62
Chapter Two Research Model and Hypotheses 65
Introduction 65
2.1 Interaction in Online Language Learning 65
2.1.1 Interactivity and Scaffolding 65
2.1.2 Scaffolding Sources Versus Preconditions 68
2.1.3 Scaffolding Features and Dimensions 72
2.1.4 Scaffolding Dimensions and Scaffolding Types 85
2.2 Online Interaction and Continuance Intention 90
2.2.1 TAM 90
2.2.2 ECM 95
2.2.3 Sense of Community 100
2.2.4 Interaction Construction 103
2.2.5 Second-Order Construct of Scaffolding 105
Summary 106
Chapter Three Methodology 108
Introduction 108
3.1 Survey Instrument 108
3.1.1 Operationalizing the Second Order Construct of Scaffolding 108
3.1.2 Developing the Survey Instrument 115
3.2 Pilot Test 122
3.3 Participants and Procedure 122
3.4 Analysis and Results 127
3.4.1 The Measurement Model 127
3.4.2 Common Method Bias 129
3.4.3 Hypothesis Testing 129
Summary 133
Chapter Four Discussion 135
Introduction 135
4.1 Online Interaction Construction 135
4.1.1 Integral Constituents of Online Interaction 135
4.1.2 Construction of Scaffolding 137
4.2 Correlation Between Interaction and Continuance Intention 145
Summary 154
Chapter Five Contributions and Implications 155
Introduction 155
5.1 Theoretical Contributions 155
5.2 Practical Implications 162
Summary 166
Conclusion 167
①Summary of Contributions 167
②Limitations 169
③Directions for Future Research 170
Biblioguapy 172
Appendixes 194
Appendix A：List of Items by Construct 194
Appendix B：Measurement Instrument 198
Appendix C：Chinese Version of Measurement Instrument 201
Appendix D：Construct Reliabilities,AVE and Correlations 203
Appendix E：Item Loadings and Cross-Loadings 204