My dad has had a job in the city since my brother and I were little, so he takes the train to work everyday and needs change to pay the meter to park his car at the train station. He would arrive home from work at about 5:30pm everyday, and there is a bell on the mudroom door that rings when it’s swung open, so when my brother and I were little, we would hear the bell and know dad was home. At one point, my dad began giving us the change left in his pocket from the parking meter for us to put in our piggy banks. We loved getting change for our piggy banks because that meant that we would eventually be able to take it to the bank and put it in a machine that would spit out cash. Soon enough, every time my brother and I heard the bell from the door swinging open, we equated that to dad giving us change for our piggy banks. We would run out to the kitchen were he came in from the mudroom to collect our change, even if it wasn’t actually dad or he didn’t have change. This is an example of classical conditioning. Classical conditioning is a phenomenon that occurs when two stimuli are repeatedly paired and the response elected by the second stimulus is eventually elicited by the first stimulus alone. The ring of the bell by the door swinging caused my brother and I to run into the kitchen thinking we were getting change for our piggy banks, no matter if that was actually the case or not. The idea of classical conditioning was mostly developed by Ivan Pavlov, who did experiments on the physiology of digestion in dogs. Dogs would salivate simply from seeing the technician who typically fed them, rather than just from food itself. Just like the dogs in Pavlov’s experiment, my brother and I would get excited at the sound of the bell ringing, rather than just the change we would receive for our piggy banks, indicating classical conditioning.