Answer:
unconditioned stimulus; conditioned stimulus
Explanation:
Every time Bert slices onions, the onions burn his eyes and tears run down his face. One day he opened the silverware drawer and pulled out the knife that he uses only to peel onions and immediately started to shed tears from the sight of the knife. In this situation, the onion is the unconditioned stimulus and the knife is the conditioned stimulus meaning that the onion is an unintended stimulus while the knife is an intended stimulus.
