Canonical models of costly signaling in international relations (IR) tend to assume costly signals speak for themselves: a signal's costliness is typically understood to be a function of the signal, not the perceptions of the recipient. Integrating the study of signaling in IR with research on motivated skepticism and asymmetric updating from political psychology, we show that individuals’ tendencies to embrace information consistent with their overarching belief systems (and dismiss information inconsistent with it) has important implications for how signals are interpreted. We test our theory in the context of the 2015 Joint Comprehensive Plan of Action (JCPOA) on Iran, combining two survey experiments fielded on members of the American mass public. We find patterns consistent with motivated skepticism: the individuals most likely to update their beliefs are those who need reassurance the least, such that costly signals cause polarization rather than convergence. Successful signaling therefore requires knowing something about the orientations of the signal's recipient.
