Based on our previous study6 we expected that OT administration would modulate attention to infant faces especially in women with high endogenous T. In line with this hypothesis, we found an interaction between the degree of BS, the treatment group and endogenous T level. OT-treated women with high endogenous T showed an attentional bias towards babies (positive Delta-RTs) compared to OT-treated women with low endogenous T (negative Delta-RTs), but only for the natural BS and this result remained on statistical trend level. We could not find further differences in the attention to babies between high and low endogenous T concentrations in the OT group, but the Delta RTs of the conditions with lower and higher BS were positive in both T groups. We suppose that adult pictures could also represent salient stimuli for nulliparous women in reproductive age, which may have rendered any behavioral effects rather small (see8 for review). Yet, the presence of a statistical trend in the OT-treated women with high endogenous T may conform to the idea that a system influenced by high levels of T may be more receptive to OT treatment, because in the female brain T could be directly converted into estradiol and thus modulate OT receptor density, which has been demonstrated in rats29.