To the degree in which a responses occurs under an antecedent stimulus. When you ask a learner “what is your name” they tell you their name, and when you ask the learner “what is their mother’s name?” they tell you their mother’s name and not their name.
The train discrimination a response is rewarded in the presence of one stimulus and not in the presence of another. For example when you show a learner a ball and they say “ball” they are rewarded, if you show them a block and they say “ball” they are not rewarded.
Comment below another example of stimulus discrimination.