The Behavioral & Cognitive Lineage

This is the largest, most researched, and most publicly visible lineage in psychotherapy. It begins with the radical claim that psychology should study observable behavior, not the unconscious — a direct rejection of psychoanalysis. Pavlov's conditioning, Watson's behaviorism, and Skinner's operant learning produced the first wave. Beck and Ellis, both disillusioned psychoanalysts, launched the cognitive revolution in the 1960s. Linehan, Hayes, Segal, and others created the third wave by reintroducing acceptance, mindfulness, and emotion — elements the first two waves had excluded. Today, cognitive-behavioral approaches account for more randomized controlled trials than all other traditions combined.