View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by UCL Discovery Capturing Hypervigilance: Attention Biases in Elevated Trait Anxiety and Posttraumatic Stress Disorder Lorna H. Stewart University College London Submitted for the degree of Doctor of Philosophy University College London September 2011 I, Lorna Helen Stewart, 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. Signed __________________________ Date __________________________ 2 Abstract The work presented in this thesis aimed to investigate attentional processing of threat in anxious individuals and its relationship to the clinical anxiety symptom of hypervigilance. Four experimental chapters report a total of nine experiments. The first three experiments (chapters 2 and 3) describe a novel paradigm designed to measure attention bias to threat in a way which overcomes limitations of previous paradigms and which differentially measures engagement and disengagement stages of attention bias. No differences in performance were seen between high and low trait- anxious individuals. Instead a general behaviour pattern was seen in which shifting location of attention aids disengagement from negative content . Additionally, adapting the task to a training paradigm demonstrated that both engagement and disengagement processes play causative roles in emotional reactivity. The series of experiments reported in chapter 4 investigated pre-conscious processing of (threat-related) traits in non-emotional faces. Highly trustworthy, untrustworthy and dominant faces (relative to neutral) took longer to reach awareness. Furthermore, the size of this effect was related to observers’ personality traits showing that preconscious evaluation of social dimensions arises from interactions between stimulus features and observer-specific traits. British war veterans showed the same effect for trustworthy faces but altered effects for faces varying in dominance traits. Finally, two eye-tracking experiments reported in chapter 5 captured hypervigilance in war veterans with and without PTSD. Veterans freely viewed photographs of neutral street scenes and a correlation was found between reported severity of hypervigilance and both number of saccades and duration of fixations. In a second experiment PTSD symptom related differences were seen in eye movements recorded whilst veterans walked London streets, although these did not match those see in the laboratory task. Overall, this thesis shows that multiple stages of processing are implicated in threat biases and that such biases in attention extend to traits other than anxiety. Additionally, anxiety-related alterations in behaviour are seen even in the absence of objective threat suggesting that preferential threat processing is only part of the picture. 3 Acknowledgments Warmest thanks to my supervisor Chris Brewin for his excellent guidance, ever-calm presence, and good humour throughout. My collaborators Bahador Bahrami, Amir Javardi, Neil Muggleton, Peter Naish and Lili Tcheang have all shown great tenacity; thank-you for agreeing to get involved. Gabriella Vigliocco bravely stepped into the secondary supervisor breach and provided encouragement in those crucial moments. And thank-you also to all the patients and participants and to students and assistants who helped with data collection as well as to my studentship providers the Medical Research Council and Geraint Rees. No thesis would ever have materialised without the members of my adopted lab, Val Curran and the Psychopharms (Celia, James, Tommy T proofreader-extraordinaire, Ravi, Les, and the many many others you have so warmly welcomed over the years); thank-you for finding space for one more. An especial and enormous thank-you to Celia Morgan and James Bisby whose coffee-fuelled science and collaborative boozing have made research cool and always kept me sane; when I grow up I want to be just like you. Thanks also to fellow thesis-heads Lorelei Howard and James Harris; further proof that every cloud has a silver lining. Too many others to mention have listened patiently, contributed words of encouragement or just passed the rum at the right moment; thank-you seems insufficient - gratitude will be delivered in person since inflicting this tome on you seems unjust returns. Finally, and most importantly, thank-you to my family; dear friends who happen to share some DNA. My little sisters, Rose and Beth, are inspirational in every regard; eldest certainly is not wisest (or tallest). An unpayable debt of gratitude is owed to my mum and dad for nurturing, nourishing, and for turning a blind eye when appropriate. It is to them I owe nearly all of my better qualities but also my foolishness in undertaking large projects and my unwillingness to quit when the going gets rough. 4 Contents Abstract ............................................................................................................................. 3 Acknowledgments ............................................................................................................. 4 List of Tables ..................................................................................................................... 9 List of Figures ................................................................................................................. 11 Chapter 1 Literature Review ...................................................................................... 13 1.1 Definitions ....................................................................................................... 14 1.1.1 Anxiety .................................................................................................... 14 1.1.2 Anxiety Disorder ..................................................................................... 15 1.1.3 Attention .................................................................................................. 16 1.2 Anxiety & Attention Biases ............................................................................ 17 1.3 Causal Links between Anxiety and Attention Biases...................................... 18 1.4 Attention Bias Theories of Anxiety ................................................................. 19 1.4.1 Williams, Watts, MacLeod, and Mathews (1988; 1997)......................... 19 1.4.2 Cognitive Motivational Analysis (Mogg & Bradley, 1998) .................... 20 1.4.3 Mathews’ & Mackintosh’s “Threat Evaluation System” ........................ 21 1.4.4 Attention Control Theory (Eysenck et al., 2007) .................................... 22 1.5 Methods for Studying Attention Biases .......................................................... 23 1.5.1 The Emotional Stroop Task ..................................................................... 23 1.5.2 The Dot Probe Task ................................................................................. 24 1.5.3 Posner’s Adapted Spatial Cueing Task ................................................... 25 1.5.4 Visual Search ........................................................................................... 26 1.5.5 Novel Methods for Assessing Attention Bias ......................................... 26 1.6 Stages of Attention Bias .................................................................................. 27 1.6.1 Orientation ............................................................................................... 28 1.6.2 Engagement ............................................................................................. 28 1.6.3 Disengagement ........................................................................................ 29 1.6.4 Avoidance ................................................................................................ 30 1.7 Looking at Causality: Attention Bias Modification ........................................ 31 1.8 Returning to the Clinic: ABM as Treatment ................................................... 33 1.9 Posttraumatic Stress Disorder ......................................................................... 34 1.10 Attentional Disturbance in PTSD .................................................................... 35 1.11 Information Processing Models of PTSD ....................................................... 38 1.12 Summary ......................................................................................................... 39 1.13 Aims and Objectives ....................................................................................... 39 Chapter 2 Attention bias in anxiety: A novel task for differentiating engagement and disengagement processes . ...................................................................................... 41 2.1 Method ............................................................................................................. 47 2.1.1 Participants .............................................................................................. 47 2.1.2 Procedure – experiment 1 ........................................................................ 48 2.1.3 Procedure – experiment 2 ........................................................................ 48 2.1.4 Materials .................................................................................................. 49 Trait Measures ....................................................................................................