The tendency for a stimulus that has been conditioned to elicit similar responses even after the response has been conditioned. The classical example is the Little Albert experiment carried out by John B. Watson and Rosalie Rayner in 1920: following a baseline period in which he was allowed to play with a white rat, the boy was subjected to a fear-inducing stimulus (loud noise due to striking a steel bar behind Albert)) at the same time as being shown the rat, with then fear being shown just by exposure to the rat. Subsequently, there was evidence for stimulus generalization (SR) in that Albert showed fear in response to similar stimuli including a rabbit, dog, fur coat and even Watson’s hair. SR occurs not only as a consequence of classical conditioning as in the Little Albert experiment, but also when operant conditioning is employed. Attempts to trace Albert later in his life led to the conclusion that he suffered from hydrocephalus at birth and eventually died from in 1925, which if the case compromises the Watson and Rayner case study as being carried out with a healthy infant.
See Classical conditioning, Hydrocephalus (or hydrocephaly), Learning, Operant (or instrumental) conditioning