Jeremy Freese recently linked to a Jason Mitchell essay that discussed perceived problems with replications. Mitchell discussed many facets of replication, but I will restrict this post to Mitchell’s claim that “[r]ecent hand-wringing over failed replications in social psychology is largely pointless, because unsuccessful experiments have no meaningful scientific value.”
Mitchell’s claim appears to be based on a perceived asymmetry between positive and negative findings: “When an experiment succeeds, we can celebrate that the phenomenon survived these all-too-frequent shortcomings. But when an experiment fails, we can only wallow in uncertainty about whether a phenomenon simply does not exist or, rather, whether we were just a bit too human that time around.”
Mitchell is correct that a null finding can be caused by experimental error, but Mitchell appears to overlook the fact that positive findings can also be caused by experimental error.
Mitchell also appears to confront only the possible “ex post” value of replications, but there is a possible “ex ante” value to replications.
Ward Farnsworth discussed ex post and ex ante thinking using the example of a person who accidentally builds a house that extends onto a neighbor’s property: ex post thinking concerns how to best resolve the situation at hand, but ex ante thinking concerns how to make this problem less likely to occur in the future; tearing down the house is a wasteful decision through the perspective of ex post thinking, but it is a good decision from the ex ante perspective because it incentivizes more careful construction in the future.
In a similar way, the threat of replication incentivizes more careful social science. Rational replicators should gravitate toward research for which the evidence appears to be relatively fragile: all else equal, the value of a replication is higher for replicating a study based on 83 undergraduates at one particular college than for replicating a study based on a nationally-representative sample of 1,000 persons; all else equal, a replicator should pass on replicating a stereotype threat study in which the dependent variable is percent correct in favor of replicating a study in which the stereotype effect was detected only using the more unusual measure of percent accuracy, measured as the percent correct of the problems that the respondent attempted.
Mitchell is correct that there is a real possibility that a researcher’s positive finding will not be replicated because of error on the part of the replicator, but, as a silver lining, this negative possibility incentivizes researchers concerned about failed replications to produce higher-quality research that reduces the chance that a replicator targets their research in the first place.