Henrich's research areas include
cultural learning, the
evolution of
cooperation,
social stratification, prestige, technological change, economic decision-making, and the evolution of
monogamous marriage and of religion. Early in his career, Henrich led teams of anthropologists and economists in conducting behavioral experiments to test the foundations of
game theory in diverse societies around the world. This body of research demonstrated that not only did the predictions of standard game theory, rooted in canonical assumptions of self-interest, fail across a diverse range of human societies, but that they failed in different ways in different places. Henrich's research on the origins and evolution of religions argues that the beliefs, rituals, and devotions that compose religious traditions have been shaped not only by reliably developing features of
human minds but also by competition among groups. Intergroup competition would have favored supernatural beliefs and ritual practices that increased within-group cooperation, harmony, or solidarity. Building on the observation that most human societies have permitted
polygamy, Henrich has argued that normative monogamy spread culturally because it reduces male-male competition and thereby promotes success in competition with other societies. Henrich's research has documented, and sought to explain, psychological differences across populations and around the world. This work argues that the most commonly used participants in psychological and behavioral research are not only a single type of population within a global spectrum, but that they are particularly psychologically peculiar. To raise the consciousness of researchers to this issue, Henrich and his collaborators dubbed the populations most commonly tapped for psychological and behavioral research as "WEIRD", a backronym that stands for "Western, Educated, Industrialized, Rich, and Democratic", and which summarizes the background of most participants in psychological research. Henrich has also written that the psychological peculiarities of "WEIRD" populations are a legacy of the influence of the medieval
Catholic Church's ban on
cousin marriage. He has argued that the isolated and vulnerable
nuclear families created by Church policies were forced to rely on and invest in new kinds of associations for the support they needed and that the growth of these associations
created the modern world (including the "peculiar" and individualistic psychology of modern people). ==Selected publications==