Final answer:
Stimulus generalization has occurred when a young child begins reacting with fear to the sight of any white jacket after associating the sight of a nurse's white uniform with fear and pain of getting an injection.
Step-by-step explanation:
When a young child learns to associate the sight of a nurse's white uniform with the fear and pain of getting an injection, and then begins reacting with fear to the sight of any white jacket, what has occurred is stimulus generalization. Stimulus generalization refers to the tendency of a conditioned response to occur in the presence of stimuli that are similar to the conditioned stimulus. In this case, the young child has generalized their fear response from the nurse's white uniform to any white jacket.