John B. Watson

In Psychology as the Behaviorist Views It, Watson argued that psychology should become an objective science of observable behavior. He rejected introspection as the field's central method and emphasized prediction and control.

Watson and graduate student Rosalie Rayner paired a loud noise with a white rat to condition fear in an infant identified as Albert B. The 1920 study became famous both as a demonstration of conditioned emotion and as an example of research that would violate modern ethical standards.

Watson established behaviorism's broad program and emphasized stimulus-response learning. Skinner later developed radical behaviorism and systematically studied operant conditioning, in which consequences alter the future frequency of behavior.

Watson resigned from Johns Hopkins University after his relationship with Rosalie Rayner became a public scandal. He subsequently built a successful career in advertising at the J. Walter Thompson agency.