1. Policymakers, like all people, tend to overestimate their chances in matters of war—much like how 80 percent of people believe their driving skills are better than average. Ken Adelman's boast in 2003 that the invasion of Iraq would be a "cakewalk" was stupid, but hardly an aberration in the history of warfare.Now that doesn't necessarily mean that people who subscribe to the hawkish worldview—in which all adversaries are implacably hostile regimes that can only be dealt with through the use of force—are always and everywhere merely delusional, suckered by their own psychological biases. In some instances, of course, a hawkish policy course might well be the correct one. As Kahneman and Renshon write, "Our conclusion is not that hawkish advisors are necessarily wrong, only that they are likely to be more persuasive than they deserve to be."
2. Similarly, policymakers, like all people, are prone to an "illusion of control," exaggerating the amount of control they have over outcomes that are important to them. At the moment, a number of U.S. policymakers seem to believe that they can still prevent a catastrophe in Iraq, or prevent Iran from developing nuclear weapons, when it's entirely likely that they can't do either.
3. Leaders in one country generally underestimate the extent to which their actions may be perceived as hostile by other countries. During the Korean War, as UN forces marched up the peninsula, Secretary of State Dean Acheson was convinced that China would understand their "non-threatening intentions." China, of course, saw things differently, and went to war. Likewise, most U.S. policymakers, Republicans and Democrats alike, dismiss the entirely reasonable possibility that Iran may be developing nuclear weapons because it fears the United States' rather ominous presence in the Middle East.
4. A psychological bias known in academic circles as "reactive devaluation" tends to undermine negotiations with adversaries. In one experiment, pro-Israeli Jews evaluated an actual Israeli-authored peace plan less favorably when it was attributed to Palestinians than when it was attributed to their own government. The other side would have to concede extra to be perceived as making a "fair" offer. Hence: "Psychologically, we are receptive not only to hawks' arguments for war, but also to their case against negotiated solutions."
5. People have a deep-seated aversion to cutting their losses. When offered a) a sure loss of $890 or b) a 90 percent chance to lose $1000 and a 10 percent chance to lose nothing, most people would take option b), even though it's statistically the worse choice.