All Things in Moderation, Including Tests of Mediation (at Least Some of the Time)

Seeking to explain the processes by which one construct causes another is a staple of psychological research. This is typically done with statistical procedures using observations of the hypothesized cause, mediator, and effect. Unfortunately, interpretations of mediation are generally weak on internal validity when using this approach. As an alternative, a causal chain approach has been advocated, but that approach is often impractical. In this article, a third method that involves measuring or manipulating a moderator is described. The core of the argument for a moderation approach hinges on the recognition that mediation refers to a mechanism or process that might be blocked or enhanced via a moderator. Thus, finding interactions with manipulations, variables, or constructs that might affect the efficiency, rate, or operation of a mechanism, or the links to or from the mechanism, implies that mechanism is involved in determining the relationship between a cause and an effect. Examples and implications regarding the potential use as well as the advantages and disadvantages of the approach for applied researchers are described.