His research focuses on the neural basis of emotional experience and expression. He investigates this topic with a number of methods including self-report, measurement of nonverbal behavior, comparative ethology, psychopharmacology, and functional brain imaging. His long-term goal is to understand the neurochemical and neuroanatomical mechanisms responsible for emotional experience and to explore the implications of these findings for the assessment and treatment of clinical disorders of affect and addiction, as well as economic behavior.