INVESTIGATING THE EXISTENCE, COGNITIVE ATTRIBUTES AND POTENTIAL PATHOLOGICAL CONSEQUENCES OF THE EXTREME FEMALE BRAIN Sarah Louise JONES Submitted for the degree of Doctor of Philosophy Division of Psychology Faculty of Social Sciences University of Bradford 2 0 1 6 Abstract INVESTIGATING THE EXISTENCE, COGNITIVE ATTRIBUTES AND POTENTIAL PATHOLOGICAL CONSEQUENCES OF THE EXTREME FEMALE BRAIN Sarah Louise Jones Key words: extreme female brain, empathising, systemising, sex differences, autism, schizophrenia, memory, cognition, gene imprinting, paranoid ideation The ‘extreme female brain’ (EFB) is derived from the empathising - systemising theory (E-S) which hypothesises that sex differences in cognition exist on a continuum, based on abilities in ‘empathising’ and ‘systemising’ (Baron-Cohen, 2003). The EFB profile; extreme empathising alongside deficient systemising, has received little attention in social cognitive neuroscience research, compared to the extreme male brain, which has advanced the knowledge of sex differences in the expression of autism. Currently, there is no solid evidence of a clinical pathology relating to the EFB nor a marker of cognition associated with a person’s ‘place’ on the E-S continuum. Here, an episodic memory paradigm with social and non-social conditions was given to participants along with measures of empathising and systemising. Scores on the social condition predicted where a person lies on the E-S continuum. The thesis then investigated the hypothesis that schizophrenia is expressed in the feminised profile (Badcock & Crepsi, 2006) i and the presumption that empathising and systemising demonstrate a trade­ off. Elements of paranoia were associated with an empathising bias. However, a bias in systemising ability was associated with schizotypy along with a significant overlap in the expression of autistic traits and schizotypy. Therefore, schizophrenia as a whole is unlikely to be the pathology seen in the EFB, rather, the positive symptoms of schizophrenia. A trade-off between empathising and systemising was seen but only in participants over 36 years. These results have significant implications for assessment and treatment of neuropsychological disorders and provide more specific details on the potential EFB pathology. ii Acknowledgments I dedicate this thesis to my Dad, who has supported me throughout my whole PhD journey. Thank you for all your encouragement and support. First and foremost, a massive thank you to my super amazing primary supervisor Dr Valerie Lesk for all her inspiration, endless encouragement, help and guidance throughout the project. I would also like to thank my 2nd supervisor Dr Gill Waters for her support throughout this project, and Rebecca Durrans for her help with recruitment of participants and statistical analysis support. Also, thank you to everyone who has come and gone from ‘E5’ for your encouragement and most importantly, friendship! I would like to say a huge, special thank you to Laura; you have supported me in every way throughout this PhD and I couldn’t be more grateful. To my whole family, thank you for all your support. Acknowledgements and thanks are owed to the Autism Research Centre at Cambridge University for making their cognitive tests and inventories available for academic use. And finally, a huge thank you to each and every one of the participants who gave their time to contribute to the project. Table of Contents Abstract j Acknowledgments ¡¡i Table of Contents jv List of Abbreviations ix Chapter 1: Thesis overview 1 1.1 Introduction and aims 1 1.2 Introducing the main concepts 6 1.3 Overview of thesis structure 9 Chapter 2: Sex differences in cognition 15 2.1 Introduction 15 2.2 Sex difference in cognitive ability 17 2.3 Neuroanatomy of sex differences 18 2.4 Biology, neurochemistry and sex hormones 21 2.5 Sex differences and disorder 24 2.6 Considerations 25 2.7 Chapter summary 27 Chapter 3: The empathising - systemising theory 29 3.1 Introduction 29 3.2 The evolution of empathising and systemising 31 3.3 Support for the E-S theory 32 3.4 Brain types 33 3.5 Biological determinants of the E-S theory 34 3.6 Neuroanatomical support 36 3.6.1 Mirror neuron system 38 3.7 Considerations 39 3.8 Chapter summary 40 Chapter 4: The extreme male brain theory of autism spectrum 42 disorder 4.1 Introduction 42 4.2 Autism spectrum disorder 42 4.3 The extreme male brain 44 4.3.1 The extreme female brain 46 4.4 Chapter summary 47 Chapter 5: The imprinted brain theory 48 5.1 Introduction 48 5.2 Overview of schizophrenia 49 5.3 Support for the imprinted brain theory 51 iv 5.4 Characterising the EFB with schizophrenia 54 5.5 Chapter summary 56 Chapter 6: Associative memory and source monitoring in 57 relation to empathising and systemising: a two-part study 6.1 Introduction 57 6.1.1 Background 57 6.1.1.1 Objective of this study 58 6.1.2 Memory ability, empathising and systemising 58 6.1.3 The neural basis of memory 60 6.1.4 Episodic memory and the development of theory of mind 61 6.1.5 Source and associative memory 64 6.1.6 Considerations 65 6.2 Aims of the study 66 6.3 Study one 67 6.3.1 Overview 67 6.3.2 Methods 68 6.3.2.1 Participants 68 6.3.2.2 Materials 68 6.3.2.3 Design 75 6.3.2.4 Procedure 75 6.4 Results 76 6.4.1 Main effects of gender 77 6.4.2 Regression analysis 78 6.4.3 Source memory (word recall) and empathising 78 6.4.4 Source memory (word recall) and systemising 80 6.4.5 Associative memory (pairing task) and empathising 80 6.4.6 Associative memory (pairing task) and systemising 82 6.5 Main findings - study one 86 6.6 Study 2 88 6.6.1 Rationale 88 6.6.2 Background - source monitoring error 89 6.6.3 Methods 93 6.6.3.1 Participants 93 6.6.3.2 Materials 94 6.6.3.3 Design 95 6.6.3.4 Procedure 96 6.7 Results 96 6.7.1 Regression analysis 97 6.7.1.1 Associative memory, empathising and systemising 97 6.7.1.2 Source monitoring error, empathising and systemising 98 6.8 Main findings - study two 99 6.9 General discussion 101 6.9.1 Interpretations 102 6.9.2 Conclusions 105 6.10 Chapter summary of key points 10g V . Chapter 7: Empathising - systemising ‘brain types’ and their 107 relationship with schizotypy, eating disorder and anxiety 7.1 Introduction 107 7.1.1 Background 1° 7 7.1.2 The extreme female brain and disordered eating 110 7.1.3 The extreme female brain and anxiety 115 7.2 The present study: research aims 117 7.3 Methods 117 7.3.1 Participants 117 7.3.2 Design 11® 7.3.3 Materials 110 7.3.4 Procedure 1^0 7.4 Results 1^0 7.4.1 Schizotypy 1^0 7.4.2 Eating disorder 1^ 3 7.4.3 Anxiety 1^4 7.4.4 Fear of negative evaluation 124 7.5 Discussion 1^4 7.5.1 Concluding remarks 120 7.6 Chapter summary of key points 128 Chapter 8: Is the ‘female brain’ more likely to be associated with 130 jumping to conclusions bias and paranoid ideation? 8.1 Introduction and background 130 8.1.1 Paranoia I 34 8.1.2 Jumping to conclusions 133 8.2 The present study: research aims 138 8.3 Methods 138 8.3.1 Participants 138 8.3.2 Design 139 8.3.3 Materials I 39 8.3.4 Procedure I 44 8.4 Results 148 8.4.1 Main effects of E-S bias 146 8.4.2 Regression analysis exploring empathising and systemising 147 8.4.2.1 Empathising 147 8.4.2.2 Systemising I 50 8.5 Discussion 1^1 8.5.1 The issue of the presumed ‘trade-off 152 8.5.2 Empathising and paranoia 153 8.5.3 Empathising and jumping to conclusions 153 8.5.4 Paranoid Ideation, jumping to conclusions bias and 154 systemising 8.5.5 Considerations 155 8.5.6 Limitations 157 8.5.7 Overall conclusion 158 8.6 Chapter summary of key points 158 vi Chapter 9: How does the AQ relate to dimensional schizotypy in 160 a neurotypical sample? 9.1 Introduction 160 9.2 The present study: research aims 165 9.3 Methods 165 9.3.1 Participants 165 9.3.2 Design 166 9.3.3 Materials 166 9.3.4 Procedure 167 9.4 Results 167 9.4.1 Regression analysis of the AQ and O-LIFE 168 9.4.2 Partial correlation 169 9.5 Discussion 170 9.5.1 Implications of results 171 9.5.2 Limitations 173 9.6 Chapter summary of key points 173 Chapter 10: Testing the continuum; does empathising and 175 systemising cognition trade-off? A two-part study considering age effects 10.1 Introduction 175 10.2 Research aims 179 10.3 Study one 181 10.3.1 Methods 181 10.3.1.1 Participants 181 10.3.1.2 Materials 182 10.3.1.3 Design 188 10.3.1.4 Procedure 188 10.4 Results 189 10.4.1 Main effect of brain type 190 10.4.2 Correlational analysis 192 10.5 Main findings - study one 194 10.6 Study 2 195 10.6.1 Methods 196 10.6.1.1 Participants 196 10.6.1.2 Materials 196 10.6.1.3 Design 196 10.6.1.4 Procedure 197 10.7 Results 197 10.7.1 Correlational analysis 197 10.7.2 Age effects 198 10.8 Main findings - study two 200 10.9 General discussion 201 10.9.1 Considerations 205 10.9.2 Limitations 207 10.10 Conclusions 207 vii 10.11 Chapter summary of key points 209 Chapter 11 : General Conclusion 211 11.1 Thesis objectives and rationale 211 11.1.1 Experimental design 214 11.2 Summaries of experimental chapters 214 11.2.1 Summary of findings 219 11.3 Implications of this thesis 221 11.4 Considerations and future directions 228 11.5 Thesis conclusion 231 References 233 Appendix 1: The EQ 281 Appendix 2: The SQ 282 Appendix 3: The Say What? Task 283 Appendix 4: O-LIFE 285 Appendix 5: EAT-26 286 Appendix 6: GAD-7 287 Appendix 7: fNE 288 Appendix 8: Paranoia Checklist 289 Appendix 9: The AQ 292 Appendix 10: Chapter 9 supplementary data 298 viii List of Abbreviations AM associative memory ANOVA analysis of variance AQ autism spectrum quotient ASD autism spectrum disorder BPD borderline personality disorder CAM-MR Cambridge mind-reading