One of the world's leading neuroscientists, Dr. Vilayanur S. Ramachandran, has written, "Our mental life is governed mainly by a cauldron of emotions, motives and desires which we are barely conscious of, and what we call our conscious life is usually an elaborate post hoc rationalization of things we really do for other reasons." There are other mental structures that govern feelings and emotions, and these structures have a greater impact on decision making than logic and reason. Moreover, emotions have much more power to affect reason than reason does to affect emotions -- particularly the emotion of fear. A scientist at Stony Brook University, Charles Taber, went so far as to say, "The Enlightenment model of dispassionate reason as the duty of citizenship is empirically bankrupt."
In the words of New York University neuroscientist Joseph LeDoux, author of The Emotional Brain, "Connections from the emotional systems to the cognitive systems are stronger than connections from the cognitive systems to the emotional systems." Our capacity for fear is "hardwired" in the brain as an ancient strategy that gives us the ability to respond instantly when survival may be at stake. But fear is not the only arousing emotion that is "hardwired" to quickly activate responses. The amygdala, for example, is almost certainly involved in speeding other responses important to our species's survival, such as the urge to reproduce. (It may be partly for that reason that sexual titillation along with fear is also a staple ingredient of modern television programming.) By contrast, reason is centered in parts of the brain that have most recently evolved and depends upon more subtle processes that give us the ability to discern the emergence of threats before they become immediate and to distinguish between legitimate threats and illusory ones.
Neurologists and brain researchers describe how disturbing images go straight to a part of the brain that is not mediated by language or reasoned analysis. There are actually two parallel pathways from the visual centers to the rest of the brain, and one of them serves as a crude but instantaneous warning system. (Evolution often forces a tradeoff between speed and accuracy.) Moreover, whatever the cause of the fear, the phenomenon itself is difficult to turn off once it's turned on. Psychologists have studied the way we make decisions in the presence of great uncertainty and have found that we develop shortcuts -- called "heuristics" -- to help us make important choices. And one of the most important shortcuts that we use is called "the affect heuristic." We often make snap judgments based principally on our emotional reactions rather than considering all options rationally and making choices carefully.
This shortcut is actually a useful trait. It allows us to make quicker decisions, and it helps us avoid dangerous situations. However, our use of emotions to make decisions can also cloud judgment. When an emotional reaction like fear is especially strong, it can completely overwhelm our reasoning process.