Pavlov’s dog would automatically and reflexively salivate (UCR) when food powder (US) was placed in its mouth. During this time the ringing of a bell(NS) elicited no response from the dog.
During conditioning
Pavlov paired the meat power (US) with the ringing of a bell (NS), by constantly ringing the bell before giving the dog meat powder until over time the dog learned to associate the two stimuli.
After conditioning
Due to the association of the two stimuli, Pavlov found that the ringing of the bell (cs) alone caused the dog to salivate (CR) despite the absence of food powder. The dog has now been conditioned to produce a reflex response to a once neutral stimulus.