As the months went on, young Albert didn't cry consistently at the sight of the white rat. So the researchers let the animal crawl against the child's chest. Watson and Rayner reported: "He first began to fret and then covered his eyes with both hands."
Thus describes one of the classic experiments in psychology, often cited in oversimplified form in Psych I textbooks to prove how conditioning can modify human emotional behavior. The 1920 study became part of social science folklore and clinched Watson's fame as the father of behaviorism.