ABSTRACT
This chapter examines how individual members of the US Congress react to armament decisions under conditions of uncertainty and how new information affects these judgments. I argue that members of Congress provide an important source of human uncertainty, reacting to new information in ways fundamentally shaped by their own prior beliefs. I use over 400 roll call votes on the defense budget from 1980 to 2017 to test a model of how members of Congress respond to new information in missile defense programs. Contrary to models of rational updating that treat information as neutral, I suggest that individual legislators engage in motivated reasoning in the face of new information. Members of Congress from a competitive electoral seat – those most concerned about the public perception of the program – respond significantly to test failures, reducing their support for missile defense. In contrast, members of Congress who receive a relatively large amount of defense money in their district double down in support for missile defense after failures.
