Answer:
The dog’s salivation without stimulus.
Explanation:
Unconditioned Response is a natural response towards the stimulus, with no learned influence.
In this case, it will be the the dog's salivation without stimulus.
Why it isn't 1: The ringing of the bell is the Conditioned Stimulus, as it is used to condition the dog that "food is served" when the bell is rung.
Why it isn't 2: The dog's salivation is the result of long-term stimulus, and so it is the Conditioned Response, where the connection between the bell and food being served is already made.
Why it isn't 3: The food is the Unconditioned Stimulus.
Learn more about Unconditioned Response, here:
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