Answer: Extinction
Explanation: In the case of classical conditioning, it is understood that a particular reinforcement, that is, a stimulus, elicits a specific response that is paired with a stimulus, and it is an acquired behaviour that is a reaction to that stimulus. This is the case for triggering a dog's reaction to a bell that is paired with food. When the food is phased out as a stimulus the dog will not respond to the bell and secrete saliva. This gradual attenuation of the stimulus response due to stimulus termination is extinction. So some acquired, learned behaviour gradually weakens and is terminated due to the abolition of the stimulus.