emphasizes a direction of influence from parents→offspring; however, we recognize that there are offspring effects on parents53, 54. If the offspring phenotype directly influences the parental phenotype, transmitted parental alleles and non-transmitted parental alleles provide quantitatively different contributions to the parental phenotype. Transmitted and non-transmitted alleles (i.e., all parental alleles) influence the parental phenotype directly. Transmitted alleles would also influence the parental phenotype indirectly through the offspring phenotype (Tp.Yo × Yp.Yo and Tm.Yo × Ym.Yo in Figure 1). This indirect path is not accounted for in our model because parental phenotypes are not regressed on offspring phenotypes. As a result, any covariance between transmitted alleles and the parental phenotype that would be explained by this indirect relationship is represented in the direct path from transmitted parental alleles. This would inflate the path from transmitted parental alleles to the parental phenotype, without affecting the path from non-transmitted parental alleles to the parental phenotype. Thus, if children’s effects on parents were a major confound, we might expect larger indirect genetic effects for transmitted compared to nontransmitted alleles. However, the indirect genetic effects were largely of the same magnitude for transmitted and nontransmitted alleles, reducing this concern. Fifth, although we statistically controlled for
