Inner speech has been implicated in Vygotsky´s theory of cognitive development. Converging evidence suggests that language skills as well as self-directed speech, in particular inner speech, is important for cognitive functions. However, the role of self-directed speech (including inner speech) in the relation between language skills and cognition have remained unclear. Despite a growing body of studies on the neural substrate of inner and overt speech, evidences of the neural differences between inner and overt speech have remained diffuse. The present dissertation aimed at filling the gap by investigating inner speech and its process of internalization with behavioral and neuroscientific methods. One study addressed the role of self-directed speech in the interplay between language skills and cognition by using the Tower of London task in children. Two studies addressed the neural correlates of the differences between inner and overt speech in adults and children during a picture-naming task by simultaneously applying the electroencephalography and functional near-infrared spectroscopy. The results of the first study confirmed that the internalization of speech is related to children´s cognition although it cannot explain the relation between language skills and problem-solving. The second study showed that inner speech is not overt speech without articulation, even more it is that prior phonological processes are downregulated. Moreover, the study showed that the brain differentiates between inner and overt speech even when no linguistic and motoric process is necessary. The results of the third study showed less differences between inner and overt speech in children indicating that inner speech is not yet adult-like. Even more it seems that inner speech represents linguistically the same like overt speech in the children´s brain.:Table of Content
Danksagung VIII
Bibliographische Darstellung X
Zusammenfassung XI
Summary XVI
Theoretical Part 1
1 Introduction and Overview 2
1.1 Introduction 2
1.2 Theoretical Background 4
1.3 Development of Inner Speech 15
1.4 Behavioral Significance of Inner Speech 17
1.4.1 The Link between Inner Speech and Cognition 18
1.4.2 The Link between Inner Speech and Language 22
1.4.3 The Link between Language Skills and Cognition 23
1.5 Psycholinguistic and Biological Significance of Inner Speech 25
1.5.1 Speech Production Model 27
1.5.2 Differences between Inner and Overt Speech in the Brain 32
1.6 Overview of the Goals and Research Questions 42
2 Study Designs and Methodologies 46
2.1 Behavioral Methods 46
2.1.1 Tower of London 46
2.2 Neuroscientific Methods 51
2.2.1 Electroencephalography 52
2.2.1.1 Physiological Principles of the EEG 52
2.2.1.2 Technical Principles of the EEG 55
2.2.1.3 EEG Frequency Bands 57
2.2.1.4 Event-related Brain Potentials (ERPs) 58
2.2.2 Functional Near-Infrared Spectroscopy 59
2.2.2.1 Physical Principles of the fNIRS 59
2.2.2.2 Physiological Principles of the fNIRS 65
2.2.2.3 Technical Principles of the fNIRS - Measurement Setup 66
Empirical Part 68
Preliminary Note 69
3 Study 1 - The role of self-directed speech in problem-solving 70
3.1 Introduction 70
3.1.1 The Association between Language Skills and Executive Functions 71
3.1.2 The association between language skills and use of self-directed speech 72
3.1.3 The role of self-directed speech in Executive Functions 73
3.1.3.1 Quantitative and qualitative analysis of self-directed speech 73
3.1.3.2 Dual-task method 74
3.1.3.3 Triggering self-directed speech 75
3.2 The present study 76
3.3 Material and Method 78
3.3.1 Participants 78
3.3.2 General procedure 79
3.3.3 Measures 79
3.3.3.1 Language Skills 79
3.3.3.2 Receptive and Expressive Vocabulary 79
3.3.3.3 Expressive Grammar 80
3.3.3.4 Receptive Grammar 80
3.3.3.5 Non-verbal intelligence (IQ) 81
3.3.3.6 Complex EF (problem-solving ability) 81
3.3.4 Coding speech 84
3.3.4.1 Quantity 85
3.3.4.2 Quality: Internalization 85
3.3.4.3 Quality: Spatial language 86
3.3.4.4 Quality: Planning function 86
3.3.4.5 Quality: Grammatical completeness 87
3.3.4.6 Interrater reliability 87
3.4 Results 88
3.4.1 Preliminary analyses 88
3.4.1.1 Factor analysis 88
3.4.1.2 Bivariate Correlations between all study measures 88
3.4.2 Main analyses 90
3.4.2.1 H1: Relation between language skills and problem-solving 90
3.4.2.2 RQ: Role of self-directed speech 91
3.4.2.2.1 RQ1: Mediation effect of self-directed speech 91
3.4.2.2.2 RQ2: Susceptibility to articulatory suppression 95
3.4.2.2.3 RQ3: Prompting self-directed speech 96
3.5 Discussion 99
3.5.1 Limitations and Next Steps 105
3.5.2 Conclusion 107
4 Study 2 - Differences between inner and overt speech in adults 108
4.1 Introduction 108
4.2 Material and Method 114
4.2.1 Participants 114
4.2.2 Material 114
4.2.3 Tasks and Procedure 115
4.3 NIRS/EEG Data Recordings 117
4.3.1 fNIRS Data Recording 117
4.3.2 EEG Data Recording 118
4.4 Data analyses 119
4.4.1 fNIRS Data Analyses 119
4.4.2 EEG Data Analyses 120
4.5 Results 121
4.5.1 fNIRS results 121
4.5.2 EEG results 122
4.6 Discussion 127
4.7 Conclusions 131
5 Study 3 - Differences between inner and overt speech in children 133
5.1 Introduction 133
5.2 Material and Method 138
5.2.1 Participants 138
5.2.2 Material 139
5.2.3 Tasks and Procedure 139
5.3 NIRS/EEG Data Recordings 141
5.3.1 fNIRS Data Recording 141
5.3.2 EEG Data Recording 143
5.4 Data analyses 143
5.4.1 fNIRS Data: Analyses 143
5.4.2 EEG Data Analyses 144
5.5 Results 145
5.5.1 fNIRS results 145
5.5.2 EEG results 146
5.6 Discussion 146
5.7 Conclusion 150
6 General Discussion 151
6.1 What role does self-directed and inner speech play in the relation between language
and cognition in children? 152
6.1.1 Quantitative and qualitative analyses of self-directed speech 152
6.1.2 Articulatory suppression of self-directed speech 155
6.1.3 Triggering self-directed speech 158
6.1.4 Conclusion 159
6.2 What distinguishes inner speech from external (overt) speech in adults? 160
6.2.1 Preparation phase 161
6.2.2 Execution phase 162
6.2.3 Conclusion 164
6.3 What distinguishes inner speech from external (overt) speech in children? 164
6.3.1 Preparation phase 165
6.3.2 Execution phase 167
6.3.3 Conclusion 169
6.4 Limitations and Future Research 169
6.5 Conclusion 176
7 References 179
Appendices 212
Coding Manual of Self-Directed Speech 213
Coding scheme 213
Coding Speech 214
Quantity of Private Speech 214
Quality of Private Speech 216
Speech Structure 216
Content Functions 218
Syntactic Features 221
Publications and Conference Contributions 222
Selbstständigkeitserklärung 225
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:71749 |
| Date | 28 August 2020 |
| Creators | Stephan, Franziska |
| Contributors | Universität Leipzig |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/acceptedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | 10.3390/brainsci10030148 |
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