Primals are beliefs about the world’s character (e.g. good, safe, enticing, or alive) that are associated with well-being and behavioral patterns. But primals’ developmental origins remain mysterious, hampering theoretical understanding and clinical efforts to change primals. This preregistered study of 905 families from 11 cultural groups adopts bioecological theory to examine (1) variance in primals accounted for by individual, family, and cultural differences, (2) concordance in primals within families, and (3) mean differences in primals across cultures. Results indicate most variance in primals is attributable to individual differences, but significant variance also emerges due to family and cultural differences. Positive correlations between mothers’ and fathers’ primals suggest assortative mating, and positive correlations between parents’ and children’s primals suggest intergenerational transmission. Findings shed light on primals’ mysterious origins: humans do appear to somehow “rub off on each other.” Clarifying this interchange can help equip clinicians to leverage primals to improve wellbeing.