The Personal Touch: Leaders’ Impressions, Costly Signaling, and Assessments of Sincerity in International Affairs1

What counts as evidence that the other side is sincere? Within mainstream international relations literature, scholars have focused on costly signals. We argue, however, that in the real world leaders do not simply look at costly signals, but they rely to an important extent on their personal impressions of other leaders, taking these as credible indicators of sincerity. Our approach thus builds both upon the literature on interstate communication and perceptions and upon more recent research in the field of neuroscience regarding affective information. To probe the plausibility of our theory, we focus on the indicators British Prime Minister Neville Chamberlain used to evaluate Germany sincerity in the late 1930s and Ronald Reagan employed to make sincerity judgments about Soviet intentions in the late 1980s. Additionally, we briefly discuss the 1961 Vienna Summit between Kennedy and Khrushchev as an illustration of how personal impressions can also result in negative assessments of sincerity. Our findings suggest that personal impressions are an important, but up until now relatively ignored, source of evidence for leaders of their counterparts’ sincerity with significant implications for threat assessments and policy choices.