Causal inference from descriptions of experimental and non-experimental research: public understanding of correlation-versus-causation.

The human tendency to conflate correlation with causation has been lamented by various scientists (Kida, 2006; Stanovich, 2009), and vivid examples of it can be found in both the media and peer-reviewed literature. However, there is little systematic data on the extent to which individuals conflate correlation with causation. In three experiments, we presented people with one of four research vignettes generated from the combination of two independent variables: whether the vignette described an experimental or non-experimental design, and whether it revealed a positive or negative association. Upon reading their vignette, participants selected inferences that could be drawn from the findings. Participants drew causal inferences from non-experimental vignettes as often as they did from experimental vignettes, and more frequently for causal statements and directions of association that fit with intuitive notions than for those that did not. We discuss our findings in relation to other biases in human thinking.