Enough already about "Black Box" experiments: Studying mediation is more difficult than most scholars suppose

The question of how causal effects are transmitted is fascinating and inevitably arises whenever experiments are presented. Social scientists cannot be faulted for taking a lively interest in "mediation," the process by which causal influences are transmitted. However, social scientists frequently underestimate the difficulty of establishing causal pathways in a rigorous empirical manner. We argue that the statistical methods currently used to study mediation are flawed and that even sophisticated experimental designs cannot speak to questions of mediation without the aid of strong assumptions. The study of mediation is more demanding than most social scientists suppose and requires not one experimental study but rather an extensive program of experimental research.