The main aim of my research is to explain why some people are more prone to anxiety than others with a view to explaining the causes, and improve the treatment of, anxiety and depression-related illnesses. To do this I follow several research strategies that are based around the theory orginated by Jeffrey Gray that the anxiety-prone personality is caused by high sensitivity to threat/punishment. My research strategies include measuring the effects of anti-anxiety drugs on the intensity of threat-avoidance behaviour in humans, studying neural activity during the same behaviour pattern, as well as evaluating associations between personality questionnaire scores and patterning of human defensive behaviour.