National leaders get all sorts of advice in times of tension and conflict. But often the competing counsel can be broken down into two basic categories. On one side are the hawks: They tend to favor coercive action, are more willing to use military force, and are more likely to doubt the value of offering concessions. When they look at adversaries overseas, they often see unremittingly hostile regimes who only understand the language of force. On the other side are the doves, skeptical about the usefulness of force and more inclined to contemplate political solutions. Where hawks see little in their adversaries but hostility, doves often point to subtle openings for dialogue.
As the hawks and doves thrust and parry, one hopes that the decision makers will hear their arguments on the merits and weigh them judiciously before choosing a course of action. Don't count on it. Modern psychology suggests that policymakers come to the debate predisposed to believe their hawkish advisors more than the doves. There are numerous reasons for the burden of persuasion that doves carry, and some of them have nothing to do with politics or strategy. In fact, a bias in favor of hawkish beliefs and preferences is built into the fabric of the human mind.
Social and cognitive psychologists have identified a number of predictable errors (psychologists call them biases) in the ways that humans judge situations and evaluate risks. Biases have been documented both in the laboratory and in the real world, mostly in situations that have no connection to international politics. For example, people are prone to exaggerating their strengths: About 80 percent of us believe that our driving skills are better than average. In situations of potential conflict, the same optimistic bias makes politicians and generals receptive to advisors who offer highly favorable estimates of the outcomes of war. Such a predisposition, often shared by leaders on both sides of a conflict, is likely to produce a disaster. And this is not an isolated example.
In fact, when we constructed a list of the biases uncovered in 40 years of psychological research, we were startled by what we found: All the biases in our list favor hawks. These psychological impulses—only a few of which we discuss here—incline national leaders to exaggerate the evil intentions of adversaries, to misjudge how adversaries perceive them, to be overly sanguine when hostilities start, and overly reluctant to make necessary concessions in negotiations. In short, these biases have the effect of making wars more likely to begin and more difficult to end.
http://www.foreignpolicy.com/story/cms.php?story_id=3660A very interesting article that's worth a read. There's some analysis of it at Pure Pedantry:
http://scienceblogs.com/purepedantry/2007/01/are_we_psychologically_prone_t.php