Effects of Peer Influence in Adolescence

[Pages:241]Effects of Peer Influence in Adolescence

Laura Kathrin Anette Wolf

UCL

Thesis submitted for Doctor of Philosophy Degree in Neuroscience

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SIGNED DECLARATION

`I, Laura Kathrin Anette Wolf, confirm that the work presented in this thesis is my own. Where information has been derived from other sources, I confirm that this has been indicated in the thesis.'

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Abstract

Adolescence is a period in life that is characterised by substantial changes in the social environment. Compared to childhood, relationships with peers gain more importance and adolescents are particularly sensitive to peer influence. Adolescents, but not adults, show increased levels of risk-taking when in the presence of peers relative to when alone. Experimental studies suggest that heightened levels of risk-taking during adolescence might be specific to affective contexts (e.g. the presence of peers), while risk-taking in non-affective contexts remains stable or decreases. In Chapter 2 of this thesis the development of the impact of two decision variables (risk and valence) on decision-making in a non-affective context during adolescence is investigated in a behavioural risk-taking task. Chapter 3 employs a functional magnetic resonance imaging (fMRI) approach to examine the development of the neural correlates of social influence during adolescence.

Previous studies have focussed on peer influence on risk-taking and little is known about the neural mechanisms of peer influence. This thesis examines whether heightened levels of sensitivity to peer influence during adolescence extend to the influence of a peer audience on tasks with either high-level (reasoning) or low-level (perceptual) cognitive components (Chapters 4 and 5). Chapter 4 investigates the effect of the presence of a peer audience on performance in a cognitively challenging task (relational reasoning), the development of this effect during adolescence and whether this effect is dependent on the identity of the audience (peer or non-peer). Chapter 5 examines the effect of the presence of a peer audience on performance in a low-level perceptual task to test whether peer audience effects would also extend to a low-level cognitive task. Chapter 6 investigates the modulation of brain activity during a high-level cognitive task (relational reasoning) by an evaluative peer audience in adolescents and adults.

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Acknowledgements I would like to thank Sarah-Jayne Blakemore and Iroise Dumontheil for their supervision and support over the last four years - both went far beyond the call of duty. I am very grateful for Sarah's generous advice and training, which eased my transition to cognitive neuroscience, as well as her enthusiasm and solution-driven guidance. Likewise, I would like to thank Iroise for all her incredibly helpful input to my research, in particular her advice towards study design, data analysis, programming and SPM, as well as her help with the fMRI data collection. I would also like to thank my collaborators Nicholas Wright, Mark Buckley and Daniel Campbell-Meiklejohn for their help with study design and data analysis. Thanks also to Emma Kilford, Anne-Lise Goddings, Emily Garrett, Narges Bazargani, Ashok Sakhardande and Kate Mills for their help with data-collection. Particular thanks to my current and former colleagues in the Blakemore lab for creating such a fun and inspiring work environment including Lisa Knoll, Emma Kilford, Delia Fuhrmann, Stefano Palminteri, Ashok Sakhardande, Emily Garrett, Hauke Hillebrandt, Lara Menzies, Luc?a Magis-Weinberg, Sarah Jensen and Narges Bazargani. Special thanks go to my two fellow PhD comrades ? Anne-Lise Goddings and Kate Mills. Thank you to the Wellcome Trust for funding my PhD and my research and to UCL, and in particular to the ICN for providing such an excellent and inspiring research environment. I am very grateful to my parents and my sister for their personal support and encouragement throughout my thesis. Finally, thank you to Axel for always being there and supporting me.

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Contents

Abstract.................................................................................................................... 3

Acknowledgements ..................................................................................................4

Abbreviations ......................................................................................................... 12

List of Tables...........................................................................................................14

List of Figures ......................................................................................................... 15

Chapter 1: Introduction...........................................................................................17

1.1 Definitions ............................................................................................................... 17

1.1.1 Defining adolescence................................................................................................................ 17 1.1.2 Defining peers........................................................................................................................... 18

1.2 Structural brain development................................................................................... 19

1.2.1 White matter development...................................................................................................... 20 1.2.2 Grey matter development ........................................................................................................ 21 1.2.3 Relating structural brain development to developmental changes in functional activation ... 24

1.3 Reward-related and risky decision making in adolescence......................................... 26

1.3.1 Decision making in affective versus non-affective contexts..................................................... 29 1.3.2 Increased responsiveness of reward-related regions during adolescence .............................. 31 1.3.3 Influence of valence on adolescent decision-making............................................................... 34

1.4 Changes in social environment and social processing during adolescence .................. 35

1.4.1 Changes in social environment................................................................................................. 35 1.4.2 Changes in social processing and development of the social brain during adolescence ......... 37

1.5 Heightened sensitivity to peer contexts during adolescence...................................... 40

1.5.1. Heightened salience of social evaluative contexts during adolescence .................................. 40 1.5.2 Sensitivity to social exclusion ................................................................................................... 41 1.5.3 Sensitivity to social approval .................................................................................................... 45

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1.6 Peer Influence.......................................................................................................... 47

1.6.1 Peer influence........................................................................................................................... 47 1.6.2 Domains of peer influence ....................................................................................................... 48

1.6.2.1 Peer influence on anti-social and risk-taking behaviours ................................................. 48 1.6.2.1.1 Observational, questionnaire-based and epidemiological measures of peer influence on anti-social and health-risking behaviours and risk-perception............................................ 48 1.6.2.1.2 Peer influence on experimental measures of risky and reward-related decisionmaking ...................................................................................................................................... 51

1.6.2.2 Beneficial peer influence................................................................................................... 55 1.6.3 Heightened sensitivity to peer influence during adolescence.................................................. 57

1.7 Social Influence........................................................................................................ 58

1.7.1 Social influence and conformity ............................................................................................... 58 1.7.2 Development of social influence and conformity .................................................................... 61 1.7.3 Social reward and punishment ................................................................................................. 63 1.7.4 Neural correlates of social influence ........................................................................................ 65 1.7.5 Developmental changes of the neural correlates of social influence ...................................... 68

1.8 Social facilitation and the audience effect................................................................. 69

1.8.1 What is social facilitation? ........................................................................................................ 69 1.8.2 Theories for the audience effect .............................................................................................. 71 1.8.3 Developmental audience effect studies ................................................................................... 73 1.8.4 Neural correlates of the audience effect.................................................................................. 74

1.9 Summary of experimental chapters .......................................................................... 75

Chapter 2: Developmental changes in effects of risk and valence.............................80

2.1 Introduction ............................................................................................................ 80

2.1.1 The effect of valence on decisions in adolescence................................................................... 81 2.1.2 Development of risk-taking in adolescence ............................................................................. 81 2.1.3 Independent effects of valence and risk on decision-making in adults ................................... 82

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2.1.4 The present study ..................................................................................................................... 83

2.2 Methods .................................................................................................................. 83

2.2.1 Participants............................................................................................................................... 83 2.2.2 Pre-test of stimulus understanding .......................................................................................... 84 2.2.3 The gambling task..................................................................................................................... 84 2.2.4 Stimulus sets............................................................................................................................. 86 2.2.5 Data analysis ............................................................................................................................. 86

2.3 Results..................................................................................................................... 88

2.3.1 Task performance ..................................................................................................................... 88 2.3.2 Influence of risk and valence on decisions ............................................................................... 88 2.3.3 Development of the influences of risk and valence on decisions ............................................ 89

2.4 Discussion................................................................................................................ 91

2.4.1 Risk-taking in adolescence is stable in this non-affective task ................................................. 91 2.4.2 The impact of valence declines across young to mid-adolescence .......................................... 92 2.4.3 Distinct developmental patterns of the impacts of risk and valence ....................................... 93 2.4.4 Limitations and implications..................................................................................................... 95

Chapter 3: Development of the modulation of the reward value signal by social influence................................................................................................................. 97

3.1 Introduction ............................................................................................................ 97

3.2 Methods ................................................................................................................ 101

3.2.1 Participants............................................................................................................................. 101 3.2.2 Experimental design ............................................................................................................... 102

3.2.2.1 Decision period ............................................................................................................... 103 3.2.2.2 Review outcome.............................................................................................................. 105 3.2.2.3 Object outcome............................................................................................................... 105 3.2.3 Data acquisition ...................................................................................................................... 106 3.2.4 Data analysis ........................................................................................................................... 107

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3.2.4.1 Behavioural data analysis................................................................................................ 107 3.2.4.2 fMRI data analysis ........................................................................................................... 108 3.2.5 Debriefing ............................................................................................................................... 110

3.3 Results................................................................................................................... 111

3.3.1 Behavioural results ................................................................................................................. 111 3.3.2 fMRI results ............................................................................................................................ 113

3.3.2.1 Agreement and disagreement with music experts ......................................................... 113 3.3.2.2 Object reward ................................................................................................................. 115 3.3.2.3 Modulation of object reward signal by music experts' opinion...................................... 117

3.4 Discussion.............................................................................................................. 118

3.4.1 Behavioural conformity in music preferences to music experts ............................................ 119 3.4.2 Social brain activation during reviewer feedback .................................................................. 121 3.4.3 Non-social and social reward activation................................................................................. 122 3.4.4 Modulation of the value signal by social influence ................................................................ 125 3.4.5 Conclusion .............................................................................................................................. 126

Chapter 4: Development of the audience effect on relational reasoning performance ............................................................................................................................. 127

4.1 Introduction .......................................................................................................... 127

4.2 Methods ................................................................................................................ 131

4.2.1 Participants............................................................................................................................. 131 4.2.2 Questionnaire measures ........................................................................................................ 132 4.2.3 Experimental design ............................................................................................................... 133

4.2.3.1 Relational reasoning task ................................................................................................ 133 4.2.3.2 Social conditions ............................................................................................................. 134 4.2.4 Data analysis ........................................................................................................................... 136

4.3 Results................................................................................................................... 137

4.3.1 Accuracy ................................................................................................................................. 137

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