Last week I attended the CHAST Templeton lecture by Joe leDoux, author of The Emotional Brain. He discussed his experiments on the fear response in rats, but I was struck by the way he explained the workings of the amygdala: when the amygdala receives scary sensory input it sends out signals to various parts of the brain that cause reflexes and other actions to kick in. There is lots of communication from the amygdala to the part of the brain that makes you react to fear, but there is barely any communication (in either direction) between the amygdala and the pre-frontal lobe, where conscious thinking takes place. Therefore, leDoux says, it's no wonder that it's so much easier for emotions to control our actions than it is for our reason to control our emotions.
That makes so much sense!