Behaviorism is a school of psychological thinking that focuses on the association between measurable stimulus and measurable behavioral response, without considering subjective experiences. In different forms, it dominated experimental psychology from the 1920s until the 1970s. Cognitivism is another school of psychological thinking that is interested in how information is processed by an organism. Cognitivism started in the 1940s and 1950s, and it has been mainstreamed in many subfields of psychological research since the 1970s when researchers from different disciplines joined information-processing psychologists to form cognitive science. This entry provides an overview of both behaviorism and cognitivism, exploring their origins, central tenets, development over time, and contributions to mass media studies.