Behaviorism is the psychological theory that suggests that humans and animals can be conditioned to respond to certain external cues, or "stimuli," in certain ways. Based in part on the early experiments of Edward Thorndike and the famous work on conditioning by Ivan Pavlov, behaviorism had, and still has wide-ranging implications, from education to advertising to rehabilitating convicted criminals. Its theoretical basis was in the utilitarian principle that people and animals are primarily concerned, and ethically speaking, ought to be concerned, with achieving the most pleasurable possible outcome. This essentially self-interested approach to human development was in a way a reaction to Freudian emphasis on the irrational. Behavioralists like John Watson and B.F. Skinner argued instead that people would naturally repeat behaviors that led to positive outcomes or responses. This, in the end, was a rational decision.