Sorry if this appears a silly question - If I understand correctly, the objective of classical conditioning, is to pair a neutral stimulus with an unconditioned stimulus, so the neutral stimulus starts producing the same unconditioned response corresponding to unconditioned stimulus. My question is - can there be multiple "levels" of stimuli that can end up producing the same unconditioned response ?
For example, referring to the famous dog salivating experiment, the dog learns to associate ringing bell stimulus with food because it was paired with food stimulus. Now if we start pairing another stimulus say, "bang the door", with "ring door-bell", would the dog be able to eventually salivate on "bang the door" stimulus ? Would it learn that "bang the door" would then be followed with "ringing door bell" and eventually "food" stimuli and thus learn multiple "levels" of associations between the stimuli ? If yes, how many such "levels" can an animal like rat or dog form these associations for ?