We conducted a series of robustness and sensitivity analyses to probe and interpret the effects from our primary analyses. For robustness analyses, we used participants’ educational attainment, assessed as highest level of education completed. Potential responses ranged from 0–17 years (primary or secondary school = actual year; technical school/1 year college = 13 years; 2 years college = 14 years; 3 years college = 15 years; 4 years college = 16 years; any graduate degree = 17 years). In sensitivity analyses of the sibling data, we used participants’ reports of their living arrangements while growing up from a set of thirteen options (see Supporting Information section 2) to evaluate whether the pattern of effects changed when the sample was limited to siblings who reported the same living arrangements (and thus likely shared the same rearing environment). An early version of the SSAGA did not query living arrangements; accordingly, we were only able to confirm that siblings grew up together for a subset of the sample (see Supporting Information section 2).
