A Dual Inheritance Perspective on Cultural Bias, Psychological Science, and Human Diversity

Psychological science has become increasingly aware that its empirical foundation relies on samples drawn from Western, Educated, Industrialized, Rich, and Democratic (WEIRD) societies. Accumulating evidence suggests that individuals from these contexts differ systematically from the majority of the world’s population—and from the broader evolutionary history of Homo sapiens—across various psychological domains. Despite this recognition, the WEIRD problem is still often framed primarily as a methodological issue of sampling bias. In this article, we clarify and consolidate existing arguments by situating the WEIRD problem within a coherent explanatory framework that generates new theoretical insights into cultural and psychological variation accessible to both psychologists and anthropologists. Drawing on a Dual Inheritance perspective, we conceptualize psychological variation as the product of interacting genetic and cultural evolutionary processes, highlighting mechanisms such as social learning, norm transmission, and institutional reinforcement. From this perspective, cultural norms, institutions, and practices are not merely background variables but active mechanisms shaping cognition across historical time. WEIRD psychological patterns are therefore interpreted not as anomalies requiring statistical correction, but as culturally evolved configurations emerging from specific ecological, institutional, and historical conditions that systematically structure learning environments and behavioral tendencies. We review four interrelated challenges associated with the overreliance on WEIRD samples and reinterpret them through a cultural evolutionary framework: limited generalizability, cultural bias and ethnocentrism, insufficient attention to within-culture variation, and the absence of historical depth in psychological explanation. Integrating evidence from psychology, anthropology, archaeology, and cultural evolution, we show these challenges are mutually reinforcing rather than independent. Finally, we outline theoretically grounded strategies for improving psychological research, emphasizing interdisciplinary collaboration, attention to underrepresented populations, and methodological pluralism.