Are effect sizes reported in highly cited emotion research overestimated relative to larger studies and meta-analyses addressing the same questions?

We assessed whether the most highly-cited studies in emotion research reported larger effect sizes compared to meta-analyses and the largest studies on the same question. We screened all reports with at least 1000 citations and identified matching meta-analyses for 40 highly-cited observational and 25 highly-cited experimental studies. Observational studies had effects greater on average by 1.42-fold (95% CI 1.09 to 1.87) versus meta-analyses and 1.99-fold (95% CI 1.33 to 2.99) versus largest studies on the same questions. Experimental studies had fold-increases of 1.29 (95% CI 1.01 to 1.63) versus meta-analyses and 2.02 (95% CI 1.60 to 2.57) versus largest studies. There was substantial between-topic heterogeneity, more prominently for observational studies. Highly-cited studies uncommonly (12/65 topics, 18%) had the largest weight in meta-analyses. They were frequently (31/65 topics, 48%) the earliest published on the topic. Highly-cited studies may offer, on average, exaggerated estimates of effects in both observational and experimental designs.