Jason Drummond UCL Engineering Doctorate for Virtual Environments, Imaging and Visualisation Towards the use of Visual Masking within Virtual Environments to Induce Changes in Affective Cognition 1 To Luca, Caroline, Mum, Dad, Marie & Jean Louis. 2 Acknowledgements I would like to thank my supervisors Anthony Steed and Nadia Berthouze for their wonderful support throughout this work. I thank my wife, Caroline, for her wholehearted, unfailing support and understanding throughout this long process. I would also like to acknowledge David Drummond and Jean Louis Pujol. I am grateful for their financial support, without which this thesis would not have materialised. I would also like to thank Mel Slater for taking the time to review the work at various stages and offering sound advice. I would also like to acknowledge and thank all of the many participants for their time and effort and the various students and staff of the Centre for Doctoral Training for their invaluable advice. This work was funded by the Engineering & Physical Sciences Research Council through its EngD VEIV Centre for Doctoral Training programme at UCL. I am very grateful to all involved. I am proud to have been, in some small way, a part of this programme. 3 I, Jason Drummond 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. ____________________________________ 4 Thesis Abstract This thesis concerns the use of virtual environments (VEs) for psychotherapy. It makes use of VE properties that go beyond real-world simulation. The core technique used is based on research found within perception science, an effect known as backwards visual masking. Here, a rapidly displayed target image is rendered explicitly imperceptible via the subsequent display of a masking image. The aim of this thesis was to investigate the potential of visual masking within VEs to induce changes in affective cognition. Of particular importance would be changes in a positive direction as this could form the foundation of a psychotherapeutic tool to treat affect disorders and other conditions with an affective component. The initial pair of experiments looked at whether visual masking was possible within VEs, whether any measurable behavioural influence could be found and whether there was any evidence that affective cognitions could be influenced. It was found that the technique worked and could influence both behaviour and affective cognition. Following this, two experiments looked further at parameter manipulation of visual masking within VEs with the aim of better specifying the parameter values. Results indicated that the form of visual masking used worked better in a VE when the target and mask were both highly textured and that affective effects were modulated by the number of exposures of the target. The final pair of experiments attempted to induce an affect contagion effect and an affect cognition-modification effect. An affect cognition- modification effect was found whereas an affect contagion effect was not. Overall, the results show that using visual masking techniques within VEs to induce affect cognition changes has merit. The thesis lays the foundation for further work and supports the use of this technique as basis of an intervention tool. 5 Table of Contents 1 INTRODUCTION ........................................................................................................................ 15 1.1 Background ................................................................................................................................... 16 1.1.1 Virtual Environments and Psychotherapy ............................................................................. 16 1.1.2 Visual Masking ..................................................................................................................... 19 1.1.3 Mood, Cognitive Bias and Implicit Self Esteem ................................................................... 21 1.2 Main Hypothesis and Research Questions ................................................................................. 25 1.3 Experiments .................................................................................................................................. 27 1.3.1 Experiment 1 ......................................................................................................................... 27 1.3.2 Experiment 2 ......................................................................................................................... 28 1.3.3 Experiment 3 ......................................................................................................................... 30 1.3.4 Experiment 4 ......................................................................................................................... 31 1.3.5 Experiment 5 ......................................................................................................................... 33 1.3.6 Experiment 6 ......................................................................................................................... 35 1.4 Contributions ................................................................................................................................ 37 1.4.1 Methodological Contributions .............................................................................................. 37 1.4.1.1 Contribution One ......................................................................................................... 37 1.4.1.2 Contribution Two ......................................................................................................... 37 1.4.1.3 Contribution Three ...................................................................................................... 37 1.4.1.4 Contribution Four ........................................................................................................ 38 1.4.2 Substantive Contributions ..................................................................................................... 38 1.4.2.1 Contribution Five ........................................................................................................ 38 1.4.2.2 Contribution Six .......................................................................................................... 38 1.4.2.3 Contribution Seven ...................................................................................................... 38 1.4.2.4 Contribution Eight ....................................................................................................... 39 1.5 Scope .............................................................................................................................................. 40 1.5.1 Virtual psychotherapy ........................................................................................................... 40 1.5.2 Visual masking ...................................................................................................................... 40 1.5.3 Facial expression, affect induction and cognition modification ............................................ 41 1.5.4 Affect contagion and self-esteem .......................................................................................... 41 1.5.5 Cognitive biases .................................................................................................................... 41 1.6 Thesis Structure ............................................................................................................................ 42 2 LITERATURE REVIEW ............................................................................................................ 43 2.1 Introduction .................................................................................................................................. 43 2.2 Psychotherapeutic Intervention via Virtual Environments ...................................................... 45 2.2.1 Introduction ........................................................................................................................... 45 2.2.2 VR & VE Psychotherapy ...................................................................................................... 48 2.2.2.1 Advantages of VEs for Psychotherapy ........................................................................ 49 2.2.2.2 Limitations of VEs for Psychotherapy ........................................................................ 54 2.2.3 Further possibilities for Virtual Therapies ............................................................................. 56 2.3 Visual Masking ............................................................................................................................. 63 2.3.1 Introduction ........................................................................................................................... 63 2.3.2 Visual Masking Taxonomy ................................................................................................... 66 2.3.3 Parameters and Priming ........................................................................................................ 73 2.3.4 Attention and Visual Masking ............................................................................................... 84 2.3.5 Masked Priming and Facial Expressions .............................................................................. 91 6 2.4 Mood, Cognitive Bias and Implicit Self-esteem