My research interests include: 1. Using psychotropic drugs as probes to explore and thereby enhance our understanding of the neurotransmitter basis of cognitive and emotional processing. 2. Differentiating the actions of different cannabinoids on schizotypal symptoms, cognition and addiction-related processes (e.g. salience; impulsivity). 3. Exploring pharmacological models of psychotic symptoms such as delusions using ketamine and cannabinoids in both challenge studies (acute administration to healthy volunteers) and natural populations of chronic users of these substances. 4. Studying users of 'recreational' drugs such as MDMA (ecstasy), cannabis ketamine to examine the short- and long-term effects of these substances on cognition, emotion and the brain. 5. Comparing recreational users with people who have become addicted to psychotropic drugs such as opiates, alcohol and ketamine in order to elucidaste processes involved in the transition from drug use to drug addiction. 6. How prescribed opiates for pain patients affect cognition, emotional processing and the perception of pain-related stimuli. 4.