Conditioning of the Human Mind

In this video, Alex is shown being conditioned by being forced to watch gruesome scenes of violence, similar to what he had done before. By making him watch these videos until he says he's feeling sick forces him to associate violence with nausea. After this occurs, the drug begins to affect him. This drug causes severe paralysis and terror, which add to the negative associations of violence.
Alex's "treatment" pretty much turns him into one of Pavlov's dogs, in the sense that he responds predictably when confronted with conditioned events. Pavlov's dogs were trained to salivate in reaction to the stimulus of hearing a bell ring. This is because they "learned" that when they hear the bell they will receive food, so their bodies begin salivating. This is similar to how Alex is conditioned, but instead of being trained to a positive reaction, he is trained to be repelled from violence.
However, the mind is very plastic; it can be trained to act a certain way, and as easily as it was trained it can untie the connections. Just as Alex is "cured" from his treatment.