When young children confront a vast array of adults' testimonial claims, they should decide which testimony to endorse. If they are unable to immediately verify the content of testimonial assertions, children adopt or reject their informants' statements on the basis of forming trust in the sources of testimony. This kind of trust needs to be based on some underlying reasons. The rational choice theory, which currently dominates the social, cognitive, and psychological sciences, posits that trust should be formed on a (...) rational basis, as a result of probabilistic assessments and utility‐maximizing calculations. In this paper, the predictions stemming from the rational choice approach to trust are systematically compared with the empirical evidence from the field of developmental psychology on how children establish their trust in testimonial statements. The results of this comparison demonstrate an obvious inadequacy of the rational choice explanation of the emergence and development of children's testimonial trust, regardless of which form of trust rationality—weighting, threshold, or ordering—is examined. As none of the three forms of rationality of children's trust in testimony squares with the empirical data, this paper introduces a new version of trust rationality, adaptively rational trust. It explores the compatibility of the concept of adaptively rational trust with the recent empirical findings in the area of developmental psychology and addresses some avenues for future research on the rationality of testimonial trust. (shrink)