Anyone who has taken intro to psychology has learned a bit about Ivan Pavlov and his research. Pavlov discovered classical conditioning by measuring the salivation of dogs when they were given food. Eventually the dogs began to respond(salivate) to the sight of the stimulus(the food) instead of the taste.
The thing that interests me about classical conditioning is its practical applications. I recently had a friend explain to me how he used this technique to train his room mate to wash his dishes more often. This video, which is the reason I chose this topic, shows a similar use of the technique.