query: When did John Dollard propose the frustration–aggression–displacement theory?
passage: Frustration–aggression hypothesis
Frustration–aggression hypothesis, otherwise known as the frustration–aggression–displacement theory, is a theory of aggression proposed by John Dollard, Neal Miller, Leonard Doob, Orval Mowrer, and Robert Sears in 1939,[1] and further developed by Neal Miller in 1941[2] and Leonard Berkowitz in 1969.[3] The theory says that aggression is the result of blocking, or frustrating, a person's efforts to attain a goal.[4]
passage: Frustration–aggression hypothesis
When first formulated, the hypothesis stated that frustration always precedes aggression, and aggression is the sure consequence of frustration.[1] Two years later, however, Miller[2] and Sears[5] re-formulated the hypothesis to suggest that while frustration creates a need to respond, some form of aggression is one possible outcome. Therefore, the re-formulated hypothesis stated that while frustration prompts a behavior that may or may not be aggressive, any aggressive behavior is the result of frustration, making frustration not sufficient, but a necessary condition for aggression.[6]