great as the observed bending) (1919) Otto Stern and Walther Gerlach conduct the Stern–Gerlach experiment, which demonstrates particle spin (1920) Enrico Fermi and his team in Rome achieved a nuclear reaction (1934, although the results were not understood until 1938, when nuclear fission was discovered by Otto Hahn and Fritz Strassmann) Enrico Fermi and Leó Szilárd build the first critical nuclear reactor (1942) John Bardeen and Walter Brattain fabricate the first working transistor (1947) Chien-Shiung Wu leads the team that disproves the conservation of parity in the Wu experiment (1956) Clyde L. Cowan and Frederick Reines confirm the existence of the neutrino in the neutrino experiment (1955) Joseph C. Hafele and Richard E. Keating show that atomic clocks flown around the world exhibit differences which are consistent with the predictions of special and general relativity. See the Hafele-Keating experiment (1971) The Scout rocket experiment confirms the time dilation effect of gravity. (1976) Alain Aspect performs the Bell test experiments in the 1980s. Eric A. Cornell and Carl E. Wieman synthesize Bose–Einstein condensate at the University of Colorado at Boulder (1995) Cockcroft–Walton generator Psychology Ivan Pavlov's experiments with dogs and classical conditioning (1900s) John B. Watson and Rosalie Rayner conduct the Little Albert experiment showing evidence of classical conditioning (1920) The Asch conformity experiments shows how group pressure can persuade an individual to conform to an obviously wrong opinion (1951) B. F. Skinner's demonstrations of operant conditioning (1930s–1960s) Harry Harlow's experiments with baby monkeys and wire and cloth surrogate mothers (1957–1974) Stanley Milgram's experiments on human obedience (1963) Walter Mischel's marshmallow experiment showing the importance to life outcomes of the ability to delay gratification (beginning late 1960s) Philip Zimbardo's Stanford prison experiment (1971) Allan and Beatrix Gardner's attempts to teach American Sign Language to the chimpanzee Washoe (1970s) Martin Seligman studies learned helplessness in dogs (1970s) Rosenhan experiment (1972). It involved the use of healthy associates or "pseudopatients", who briefly simulated auditory hallucinations in an attempt to gain admission to 12 different psychiatric hospitals. The hospital staff failed to detect a single pseudopatient. The study is considered an important and influential criticism of psychiatric diagnosis. Kansas City preventive patrol experiment (1972–1973) It was designed to test the assumption that the presence (or potential presence) of police officers in marked cars reduced the likelihood of a crime being committed. No relationship was found. Elizabeth Loftus' and John C. Palmer's car crash experiment