Pavlov's Classical Conditioning #WordlessWednesday

In Pavlov's famous experiment, he would make a unique sound with a metronome before giving food to the dogs. Soon, just the sound of the metronome would make the dogs salivate even if no food was there because they now associated that sound with food.
This is called Classical Conditioning. 
And it is not restricted to pooches, either. You and I undergo it every day. The anger you feel when you see a particular politician you hate even if he has not said anything new. The hope you...