The influence of the endogenous T concentration (measured out of one saliva sample that was collected directly before administration) on attention to babies was analyzed with a 3 (morph type: low BS, natural BS and high BS) × 2 (treatment: OT vs. placebo) × 2 (T: median split of the sample that was collected directly before administration) ANOVA. Of particular interest was the significant three-way interaction between the factors “morph type”, “treatment” and “T” (F2,104 = 4.359; p = 0.015; see Table S1 for details). Building on previous research6 we assumed that women with high endogenous T derive greater benefit from OT treatment than women with low endogenous T and hence will become more sensitive for the BS. We found that OT-treated women with high endogenous T exhibited an attentional preference for the natural BS (positive Delta-RT: MhighT = 6.4 ± SEM 24.2 ms) compared to OT-treated women with low endogenous T (positive Delta-RT: MlowT = −50.6 ± SEM 16 ms) but these results remained on statistical trend level [Bonferroni-corrected statistical threshold was p ≤ 0.0166 (t27 = 1.86, p = 0.03; one-tailed, a priori hypothesis based on6)]. In the placebo group women with low endogenous T directed less attention to the plus morphed babies (MlowT = −39.1 ± SEM 21.3 ms) than women with high T concentrations (MhighT = 23.4 ± SEM 14.6 ms; t25 = 2.29, p = 0.015, one-tailed, a priori hypothesis based on6). The placebo-treated participants with high or low T did not show any differences in the preference for the natural BS.