When cognitive behaviour therapy emerged in 1950s, driven by the work of Albert Ellis and Aaron Beck, basic behaviour principles were largely sidelined in clinical psychology curricula. Issues in cognition became the focus of case conceptualisation and intervention planning for most therapists. But as the new "third-wave" behaviour therapies begin to address weaknesses in the traditional cognitive behavioural models - principally the modest effectiveness of thought stopping and cognitive restructuring techniques - basic behaviour principles are once again attracting the interest of front-line clinicians. Many of today's clinicians, though, received their training during the years in which classical behaviourism was not a major part of clinical education. In order to make the best use of the new contextual behaviourism, they need to revisit basic behavioural principles from a practical angle. This book addresses this need. "The ABCs of Human Behavior" offers practicing clinicians a practical introduction to the basics of modern behavioural psychology.