Answer:
neutral; response-producing
Explanation:
The experiments by Pavlov demonstrated how a "neutral" or also called unconditioned stimulus, was paired with a "response-producing" or conditioned response. This means that an association created between them would enable dogs to learn something unknown and new to them.
When dogs listened to a sound (a bell ringing), they learned that food was approaching to they began to salivate, for they would receive food shortly after.
After some time, dogs kept listening to a bell, but the food was no longer provided, and still, they kept salivating as if the food was there.
Therefore, they had already had a conditioned response!
