Abstract: Psychology must confront the bias in its broad literature towards the study of participants developing in environments unrepresentative of the vast majority of the world’s population. Here, we focus on the implications of addressing this challenge, highlight the need to address over-reliance on a narrow participant pool, and emphasize the value and necessity of conducting research with diverse populations. We show that high impact-factor developmental journals are heavily skewed towards publishing papers with data from WEIRD populations (Western, Educated, Industrialized, Rich and Democratic). Most critically, despite calls for change and supposed widespread awareness of this problem, there is a habitual dependence on convenience sampling and little evidence that the discipline is making any meaningful movement towards drawing from diverse samples. Failure to confront the possibility that culturally-specific findings are being misattributed as universal traits has broad implications for the construction of scientifically defensible theories and for the reliable public dissemination of study findings.