Behaviorism is a philosophical movement begun early 20th century that has given rise to two important applications in clinical settings. One branch derives from the work of Pavlov and Watson and classical conditioning, the other from Thorndike and Skinner and operant conditioning. Clinicians working in the [Page 15]operant behavioral tradition have been known as behavior modifiers or applied behavior analysts, and occasionally, as radical behaviorists. Historically, applied behavior analysts have conducted clinical work in institutional settings with children and adults with developmental disabilities or in schools with typically developing children. By contrast, clinicians working in the classical conditioning paradigm identify as behavior therapists. Practitioners of behavior therapies have been more closely associated with clinical work in adult outpatient settings, ...