Albert Bandura famously conducted the Bobo doll experiment which demonstrated observational learning. Margaret and Harry Harlow conducted experiments with monkeys, showing the importance of "contact comfort" for healthy social development and attachment. Ivan Pavlov conducted the famous classical conditioning experiment, pairing a bell ringing with food to elicit salivation in dogs. B.F. Skinner conducted experiments demonstrating concepts of operant conditioning. Milgram's famous experiment demonstrated ground-breaking findings involving obedience. Philip Zimbaro's Standford Prison experiment demonstrated shocking psychological effects of the prisoner and guard dynamic.