The Epistemic Importance of Establishing the Absence of an Effect

In psychology as in many other sciences, Popperian rhetoric remains strong, even though Popperian practice has never been. Here, we provide an introduction to the four main approaches to epistemic justification, outlining the importance of null results in each and emphasizing the importance of each approach in developing a cumulative scientific literature. We argue that whether or not we subscribe to the Popperian Hypothetico-Deductive (HD) model of science, there is value in adopting Popper's advice about creating bold conjectures and risky tests for establishing the absence (or presence) of effects. However, the most popular approach to statistical testing, Null Hypothesis Significance Testing practice fails at both, and has arguably supported the censoring of null results from our scientific literature. Allowing null results into the scientific literature is essential for a cumulative science to function. However, we argue that even a repaired Popperian HD process won't offer much advice about what are interesting and important absences (or presences) to pursue. For answers to those fundamental questions, we need to appeal to other forms of epistemic justification such as those presented in this article.