Final answer:
The baby's behavior of crying with strangers and smiling with the mother is an example of stimulus discrimination, indicating a learned response specific to the conditioned stimulus— the mother's face.
Step-by-step explanation:
The baby that cries in response to faces of strangers but smiles when seeing the mother's face is exhibiting stimulus discrimination. This is a conditioning phenomenon where the baby has learned to respond differently to various stimuli that are similar, demonstrating the conditioned response only to the conditioned stimulus which, in this case, is the mother's face.
This is distinctly different from stimulus generalization, where the conditioned response is elicited by stimuli similar to the conditioned stimulus, and from higher-order conditioning, where a conditioned stimulus is paired with a new neutral stimulus, creating a second (often weaker) conditioned stimulus. Lastly, response generalization refers to providing the conditioned response to a broader range of stimuli than the conditioned stimulus, which also does not describe the specific behavior of the baby in this scenario.