Stefan G. Hofmann, PhD, is a professor in Boston University's department of psychological and brain sciences clinical program, where he directs the Psychotherapy and Emotion Research Laboratory (PERL). His research focuses on the mechanism of treatment change, translating discoveries from neuroscience into clinical applications, emotions and cultural expressions of psychopathology. He is past president of the Association for Behavioral and Cognitive Therapies (ABCT) and the International Association for Cognitive Psychotherapy. He is also editor in chief of Cognitive Therapy and Research and is associate editor of Clinical Psychological Science. He is author of many books, including An Introduction to Modern CBT and Emotion in Therapy.