In Pavlov's experiment the conditioned stimulus is a previously neutral stimulus (like the bell), that eventually elicits a conditioned response (drooling) after being repeatedly paired with the unconditioned stimulus (food).
Explanation:
The conditioned stimulus studied by Pavlov is any internal or external stimulus that initially causes no reaction in an organism, ie the conditioned stimulus was initially a neutral stimulus. However, through a classic conditioning process, you can create a response to this stimulus. The conditioned stimulus is the counterpart of the unconditioned stimulus.
The study of how both elements are related is the basis of conditioning and behavioral psychology. It was first studied by scientist Ivan Pavlov in his famous experiment in which he was able to salivate dogs by ringing a bell.
