Stimulus Generalization is when an organism responds to a new stimulus in the same way as a previously encountered stimulus, based on similarity of the stimuli and the organism’s history of reinforcement with the previous stimulus.
For example, imagine a very young boy encountering different breeds of dogs for the first time. When he sees a Labrador retriever and he responds “dog!”, his parents reward him with praise and he learns that the animal is indeed a dog. When the child sees a Shih Tzu and he responds “dog!”, he is also rewarded with praise. The boy responds the same way to both types of dog stimuli, and each response generates the same result. In this way the child learns to call all dog breeds “dogs,” even though they are of different sizes and have different types of fur, etc.