As expected, the decision to support the strike felt much more difficult when one or more Americans had died.Why did U.S. President Donald Trump recently call off a retaliatory strike against Iran?The answer was proportionality: Trump said the American response to Iran’s downing of an American drone should be on a similar scale.That decision, Trump said, came from his “gut.”Because the drone was unmanned, Trump said it would be disproportionate for a U.S. strike to result in approximately 150 Iranian deaths, the estimated number of likely casualties.The decision to call off the strike at the last minute may have been the right one. But years of research on valuing human lives, conducted by us and many others, make a compelling case that deciding what is proportional based on gut feelings is a profound mistake.A decision-making process that relies on intuitive feelings, rather than careful deliberation, invites a host of biases that make bad decisions, and disproportional consequences, far more likely.
