We thank Eckles et al. (1) for their thoughtful comments. The authors point out that the optimization algorithms of Facebook’s advertising platform constitute a potential confound of campaign outcomes. We agree, in general, that such algorithms could pose a threat to the validity of field studies since they introduce unintended variance across the target audiences. However, as we demonstrate below, it is unlikely that such confounds account for the pattern of results presented in our original research (2).