(with Avi Acharya and Maya Sen)

We present an approach to investigating causal mechanisms in experiments that include mediators, in particular survey experiments that provide or withhold information as in vignettes or conjoint designs. We propose an experimental design that can identify the controlled direct effect of a treatment and also, in some cases, what we call an intervention effect. These quantities can be used in ways to address substantive questions about causal mechanisms, and can be estimated with simple estimators using standard statistical software. We illustrate the approach via two examples, one on characteristics of U.S. Supreme Court nominees and the other on public perceptions of the democratic peace.