Even more importantly, the positive correlation between increased selective attention to babies and activation in the left putamen only remained significant in the high endogenous T group after OT administration. Only a few behavioral studies have so far examined the interactions between OT and T in women, and, to the best of our knowledge, our study is the first that used functional neuroimaging to assess the underlying neural mechanism. Here we used the T sample that was collected directly before administration to capture the current T state of the participant and not the habitual concentration, because we could not control for daytime fluctuations. This method also allows the comparability with previous research26,45,46. The single T sample collection before administration provided the opportunity to analyze the real-time T concentration at the measuring time. But, for the same reasons, we cannot exclude further T fluctuations that might have occurred during scanning, which may have weakened the stability of this single measurement and might therefore constitute a potential limitation of this study. However, the T concentration before administration and post-test concentration after measurement were highly correlated (r = 0.447; p < 0.001). This may suggest that T concentration may have been relatively stable during the actual scanning period.