Ivan Pavlov (1849-1936) won the 1904 Nobel Prize for physiology for research he had done on the digestive system. He was known especially for experiments in behavioral conditioning involving his dogs. Every day, before feeding his dogs, he would ring a little bell. Eventually, he got his dogs to where he could ring the bell, even if there was no food, and the dogs would still begin salivating.
There is not a single defined condition where you would use this allusion, but generally, if someone gets into a pattern of always expecting one thing to follow another, in a way they become like Pavlov's dog.
I've claimed before that the theme song to the show Mama's Family has this effect on me. Every day, it came on at 4:30pm, right as my dad was getting home. I always had to turn the show off 5 minutes into it because that's when we would eat dinner. When I hear it, I still get hungry and I remember smells of chicken, mashed potatoes, and macaroni and cheese.
A good example of this is also in the hit TV series The Office, where Jim does a similar experiment on Dwight. Several times a day, every day, Jim gets an error "ding" noise on his computer, and when he does it, he immediately offers Dwight an Altoid mint. I'll let you see the episode for yourself if you want to know the outcome. :-) It's one of my favorite scenes from any of the shows.