Zwaan et al. make the classic distinction between exact replications (using the same operations as in an original study) and conceptual replications (using different materials to instantiate the independent variables [IVs] and/or dependent variables [DVs]). They argue that exact replications are superior and therefore original authors should provide a “replication recipe” providing considerable detail about the specific operations used so others can duplicate one's study. Furthermore, Zwaan et al. claim that a finding is “not scientifically meaningful until it can be replicated with the same procedures that produced it in the first place” (sect. 6, para. 1). Instead, I argue that for much theoretical work in psychology, use of the same operations is not what is critical, but rather instantiation of the same concepts. Thus, theory testing researchers should emphasize conducting exact conceptual replications (ECRs) where the goal is to repeat as closely as possible not the precise methods of the original study, but to instantiate the same conceptual meaning of the original variables in the same conceptual context (Petty Reference Petty2015).

In the physical sciences, the emphasis on carefully replicating operations is often reasonable. For instance, when mixing hydrogen and oxygen to create water, the choice of operations to represent the hydrogen and oxygen concepts is constrained because there is a tight link between concepts and operations (i.e., the operations and concepts are basically the same). Furthermore, the operations chosen are likely to represent the concepts across virtually all contexts. Thus, if you reasonably do the same thing, you should get the same result. In contrast, in many theory testing psychology studies, the choice of operations to represent concepts is vast and the link between the two is not assured. Thus, conducting a replication that is as close as possible to the original study will not necessarily help with replicability because the meaning of the original IVs and DVs in the new context may have changed.

Consider a psychologist mixing a credible source with a persuasive message to produce favorable attitudes toward some proposal. When Hovland and Weiss (Reference Hovland and Weiss1951) did this, Robert Oppenheimer was used as a credible source, and the Russian newspaper, Pravda, was the low credible source on the topic of building atomic submarines. Oppenheimer produced more favorable attitudes than Pravda. It seems unlikely that the same operations would produce the same result today. Does this render the original study scientifically meaningless? No. The initial result is meaningless only if you cannot conduct an ECR. ECRs are important because what we ultimately want to know is not whether Oppenheimer produces more favorable attitudes toward submarines than Pravda, but whether credibility affects persuasion.

The initial credibility study results would be meaningful if the study can be replicated in an ECR. Original authors can specify the criteria any replication study should meet. Namely, provide the conceptual recipe. This differs from the operational recipe that Zwaan et al. favor. Thus, if manipulating credibility, instead of only articulating operational details like replicators must have people see an 8 X 10 picture of the source with an 18 word description, original authors could also indicate that the high credibility manipulation should produce a rated level of credibility of 7 on an 11 point credibility scale and the low credibility condition should be at 4. But, it is not sufficient for replicators to produce a successful manipulation check. If the original study had high and low credibility means of 7 and 4 but the replication study had means of 1 and 4, the manipulation check in the replication study would seem “successful” (and the effect size of the manipulation check might be comparable to the original), but, the placement of the manipulation along the credibility continuum would be quite different and thus inappropriate for an ECR. In addition to providing information about the statistical properties of the IV manipulation check, original authors should specify what constructs the IV should not vary. Thus, original authors should not only provide the IV information just noted, but also what concepts should be assessed to ensure they are not confounded (e.g., source attractiveness and power).

Critically, similar arguments apply to the DV. In the chemistry example, the dependent variable (water) is easily assessed. However, there are multiple ways to assess favorable evaluations (e.g., explicit vs. implicit measures). Now consider a different original study in which investigators are examining the frustration to aggression link. These researchers should indicate how to determine if the dependent measure taps aggression. The original study might have measured how many teaspoons of hot sauce were administered, but in a replication attempt in Mexico, giving hot sauce may not signal aggressiveness. Thus, specifying what criteria the DV should meet (to gauge its conceptual meaning) is as important as specifying this for the IVs. For example, participants can rate how aggressive it is to give hot sauce.

Finally, the overall level of the DV on the aggression continuum in the new context is important. This is because unlike the chemistry example where there is only one way to produce water, psychology DVs are often multiply determined. There are many ways to produce aggression and there may be factors in the replication context that affect the hot sauce DV that were not present in the original research. Some of these may be alternative causes of aggression (e.g., hot temperature), but others may influence giving out hot sauce for other reasons (e.g., its popularity or price in the culture). Each can be problematic and lead to replication failure. Thus, a replication recipe should focus on describing contextual factors that are plausibly linked to the DV. Most simply, one can report the mean level of the operational (amount of hot sauce) and conceptual (link to aggressiveness) DV in a control condition in which none of the critical IVs are varied. This is needed to assure that relevant background variables in the replication study that affect the DV are set at a similar level to the original study.

In sum, conceptually driven psychology research is different from the physical sciences, and our replication recipes should reflect this.