Why does university exposure to a hierarchy-attenuating (HA) academic major (e.g., social science) lead to a decrease in anti-egalitarianism and group domination (social dominance orientation, SDO)? The reason for this well-documented phenomenon remains unclear. In the social sciences, the origins of differences in both behavior and personality are attributed more to social and environmental factors than to genetic ones. We hypothesized that the normative and informational influences of this academic major would lead to perceptions that genes have a less important role than nurture in the shaping of human behavior and personality. Our main hypothesis was confirmed. Decreased SDO among psychology students was mediated significantly by a decrease in belief in genetic determinism, the factor we called “geneticism.” Copyright © 2008 John Wiley & Sons, Ltd.