Dissemination biases in ecology: effect sizes matter more than quality


E. K. Barto, Inst. für Biologie, Dahlem Center of Plant Sciences, Freie Univ. Berlin, Altensteinstraße 6, DE-14195 Berlin, Germany. barto@zedat.fu-berlin.de


Publication and citation decisions in ecology are likely influenced by many factors, potentially including journal impact factors, direction and magnitude of reported effects, and year of publication. Dissemination bias exists when publication or citation of a study depends on any of these factors. We defined several dissemination biases and determined their prevalence across many sub-disciplines in ecology, then determined whether or not data quality also affected these biases. We identified dissemination biases in ecology by conducting a meta-analysis of citation trends for 3867 studies included in 52 meta-analyses. We correlated effect size, year of publication, impact factor and citation rate within each meta-analysis. In addition, we explored how data quality as defined in meta-analyses (sample size or variance) influenced each form of bias. We also explored how the direction of the predicted or observed effect, and the research field, influenced any biases. Year of publication did not influence citation rates. The first papers published in an area reported the strongest effects, and high impact factor journals published the most extreme effects. Effect size was more important than data quality for many publication and citation trends. Dissemination biases appear common in ecology, and although their magnitude was generally small many were associated with theory tenacity, evidenced as tendencies to cite papers that most strongly support our ideas. The consequences of this behavior are amplified by the fact that papers reporting strong effects were often of lower data quality than papers reporting much weaker effects. Furthermore, high impact factor journals published the strongest effects, generally in the absence of any correlation with data quality. Increasing awareness of the prevalence of theory tenacity, confirmation bias, and the inattention to data quality among ecologists is a first step towards reducing the impact of these biases on research in our field.