Although replication is a central tenet of science, direct replications are rare in psychology. This research tested variation in the replicability of thirteen classic and contemporary effects across 36 independent samples totaling 6,344 participants. In the aggregate, ten effects replicated consistently.One effect -imagined contact reducing prejudice -showed weak support for replicability. And two effects -flag priming influencing conservatism and currency priming influencing system justification -did not replicate. We compared whether the conditions such as lab versus online or U.S. versus international sample predicted effect magnitudes. By and large they did not. The results of this small sample of effects suggest that replicability is more dependent on the effect itself than on the sample and setting used to investigate the effect. Word Count = 121 words Many Labs 3 Investigating variation in replicability: A "Many Labs" Replication ProjectReplication is a central tenet of science; its purpose is to confirm the accuracy of empirical findings, clarify the conditions under which an effect can be observed, and estimate the true effect size (Brandt et al., 2013; Open Science Collaboration, 2012. Successful replication of an experiment requires the recreation of the essential conditions of the initial experiment. This is often easier said than done. There may be an enormous number of variables influencing experimental results, and yet only a few tested. In the behavioral sciences, many effects have been observed in one cultural context, but not observed in others. Likewise, individuals within the same society, or even the same individual at different times (Bodenhausen, 1990), may differ in ways that moderate any particular result.Direct replication is infrequent, resulting in a published literature that sustains spurious findings (Ioannidis, 2005) and a lack of identification of the eliciting conditions for an effect. While there are good epistemological reasons for assuming that observed phenomena generalize across individuals and contexts in the absence of contrary evidence, the failure to directly replicate findings is problematic for theoretical and practical reasons. Failure to identify moderators and boundary conditions of an effect may result in overly broad generalizations of true effects across situations (Cesario, 2013) or across individuals (Henrich, Heine, & Norenzayan, 2010). Similarly, overgeneralization may lead observations made under laboratory observations to be inappropriately extended to ecological contexts that differ in important ways (Henry, MacLeod, Phillips, & Crawford, 2004). Practically, attempts to closely replicate research findings can reveal important differences in what is considered a direct replication (Schimdt, 2009), thus leading to refinements of the initial theory (e.g., Aronson, 1992, Greenwald et al., 1986. Close replication can also lead to Many Labs 4 the clarification of tacit methodological knowledge that is necessary to elicit the effect of interest (Collins,...

We conducted preregistered replications of 28 classic and contemporary published findings, with protocols that were peer reviewed in advance, to examine variation in effect magnitudes across samples and settings. Each protocol was administered to approximately half of 125 samples that comprised 15,305 participants from 36 countries and territories. Using the conventional criterion of statistical significance ( p < .05), we found that 15 (54%) of the replications provided evidence of a statistically significant effect in the same direction as the original finding. With a strict significance criterion ( p < .0001), 14 (50%) of the replications still provided such evidence, a reflection of the extremely high-powered design. Seven (25%) of the replications yielded effect sizes larger than the original ones, and 21 (75%) yielded effect sizes smaller than the original ones. The median comparable Cohen’s ds were 0.60 for the original findings and 0.15 for the replications. The effect sizes were small (< 0.20) in 16 of the replications (57%), and 9 effects (32%) were in the direction opposite the direction of the original effect. Across settings, the Q statistic indicated significant heterogeneity in 11 (39%) of the replication effects, and most of those were among the findings with the largest overall effect sizes; only 1 effect that was near zero in the aggregate showed significant heterogeneity according to this measure. Only 1 effect had a tau value greater than .20, an indication of moderate heterogeneity. Eight others had tau values near or slightly above .10, an indication of slight heterogeneity. Moderation tests indicated that very little heterogeneity was attributable to the order in which the tasks were performed or whether the tasks were administered in lab versus online. Exploratory comparisons revealed little heterogeneity between Western, educated, industrialized, rich, and democratic (WEIRD) cultures and less WEIRD cultures (i.e., cultures with relatively high and low WEIRDness scores, respectively). Cumulatively, variability in the observed effect sizes was attributable more to the effect being studied than to the sample or setting in which it was studied.

We conducted preregistered replications of 28 classic and contemporary published findings with protocols that were peer reviewed in advance to examine variation in effect magnitudes across sample and setting. Each protocol was administered to approximately half of 125 samples and 15,305 total participants from 36 countries and territories. Using conventional statistical significance (p &lt; .05), fifteen (54%) of the replications provided evidence in the same direction and statistically significant as the original finding. With a strict significance criterion (p &lt; .0001), fourteen (50%) provide such evidence reflecting the extremely high powered design. Seven (25%) of the replications had effect sizes larger than the original finding and 21 (75%) had effect sizes smaller than the original finding. The median comparable Cohen’s d effect sizes for original findings was 0.60 and for replications was 0.15. Sixteen replications (57%) had small effect sizes (&lt; .20) and 9 (32%) were in the opposite direction from the original finding. Across settings, 11 (39%) showed significant heterogeneity using the Q statistic and most of those were among the findings eliciting the largest overall effect sizes; only one effect that was near zero in the aggregate showed significant heterogeneity. Only one effect showed a Tau &gt; 0.20 indicating moderate heterogeneity. Nine others had a Tau near or slightly above 0.10 indicating slight heterogeneity. In moderation tests, very little heterogeneity was attributable to task order, administration in lab versus online, and exploratory WEIRD versus less WEIRD culture comparisons. Cumulatively, variability in observed effect sizes was more attributable to the effect being studied than the sample or setting in which it was studied.

Although replication is a central tenet of science, direct replications are rare in psychology. This research tested variation in the replicability of thirteen classic and contemporary effects across 36 independent samples totaling 6,344 participants. In the aggregate, ten effects replicated consistently. One effect – imagined contact reducing prejudice – showed weak support for replicability. And two effects – flag priming influencing conservatism and currency priming influencing system justification – did not replicate. We compared whether the conditions such as lab versus online or U.S. versus international sample predicted effect magnitudes. By and large they did not. The results of this small sample of effects suggest that replicability is more dependent on the effect itself than on the sample and setting used to investigate the effect.

Many studies show relationships between birth order and intelligence but use cross-sectional designs or manifest other threats to internal validity. Multilevel analyses with a control variable show that when these threats are removed, two major results emerge: (a) birth order has no significant influence on children's intelligence and (b) earlier reported birth order effects on intelligence are attributable to factors that vary between, not within, families. Analyses on 7- to 8 - and 13- to 14-year-old children from the National Longitudinal Survey of Youth support these conclusions. When hierarchical data structures, age variance of children, and within-family versus between-family variance sources are taken into account, previous research is seen in a new light.