DISCLAIMER: If you are easily offended/grossed out, do not continue reading.
In the 1920's Ivan Pavlov demonstrated a form of associative learning he called Classical Conditioning, or Pavlovian Conditioning. This experiment describes a type of learning in which there is no relation between the behavior of an animal and a biologically relevant event.
An animal is given a conditioned stimulus (CS), and at first shows no response (conditioned response, CR). However, when an unconditioned stimulus (US) is added an unconditioned response (UR) is seen. After a while, when the CS is given, the US and the UR become irrelevant and the CR is seen.
Let me explain...
My BF was a great sport and would call me every morning at 6 to wake me up. I personally think the sound of an alarm clock is the worst-sound-in-the-world, so hearing his lovely Dropkick-Murphy's-ringtone made greeting the morning a little easier. At first he would call, and nothing would happen... I'd sleep maybe 5 more minutes, and then wake up and go to the bathroom. After a few weeks, this became routine.
NOW, 8 months later, I have become a product of classical conditioning.
Every time I hear BF's ringtone (CS) I have to go pee (UR)!!!! It doesn't matter what time of day it is, or where I am at, I need to find a bathroom. At first I thought I was nuts and was imagining it. However, I brought it up to BF in December, and he told me that he had noticed every time he called I mentioned I had to pee. He now calls me at inappropriate times, and ungodly hours of the night.