Although international relations (IR) theorists generally assume that actors update their beliefs about the intentions of adversaries and allies based on structure, costly signaling, and past actions, little is known about how the process of rapprochement between adversaries differs from the process of alienation between allies, particularly with respect to the nature and degree of costly signaling. Furthermore, until recently the role of the individual in these processes has only been engaged by a small number of scholars, and fewer still have integrated this perspective with conventional approaches to rapprochement and alienation. Drawing from findings in social psychology, We present results from an original survey experiment showing that (1) political belief systems are a powerful determinant of how individuals perceive the intentions of other states, more so than an observed state's signaling behavior; (2) there are diminishing returns in increasing the cost of a signal; and (3) hostile signals are more effective in signaling intent than reassuring signals.In international relations, communication between states is inherently difficult. States often have reasons to misrepresent their interests, capabilities, and resolve. During the Cold War, how could the United States credibly threaten to launch a nuclear strike if faced with Soviet aggression against an ally? More recently, how were American and Iranian leaders to know whether the other would fulfill their obligations under the nuclear deal? Looking forward, how can North Korean and American leaders ever establish trust? After decades of antagonism and mistrust, how can international adversaries clearly show that they will keep their word? How can relations be improved? One method of enhancing the credibility of a signal is by making it "costly." For example, public statements of intentions are viewed as costly because the leader's reputation may suffer if they do not keep their word.In this article, we examine psychological factors that influence whether an individual updates their prior beliefs about the intentions of a state in the face of costly signals. International relations (IR) theory places a great deal of focus on the effects of costly signaling, the perceived hostile intent of adversaries, and to a lesser degree, the perceived benign intent of allies. Yet we still understand little about the psychology of belief updating as it pertains to the process of rapprochement between 0162-895X