Oxytocin
It has been shown that oxytocin differentially affects males and females. Females who are administered oxytocin are overall faster in responding to socially relevant stimuli than males who received oxytocin. Additionally, after the administration of oxytocin, females show increased amygdala activity in response to threatening scenes; however, males do not show increased amygdala activation. This phenomenon can be explained by looking at the role of gonadal hormones, specifically estrogen, which modulate the enhanced threat processing seen in females. Estrogen has been shown to stimulate the release of oxytocin from the hypothalamus and promote receptor binding in the amygdala.
Endocrinology of parenting
However, experimental results are less conclusive. Nulliparous mice do not respond to pup calls, but when administered with oxytocin, they do. A similar study conducted by Holmon and Goy tested nulliparous rhesus females, where post injection did not elicit a drastic response to infants, however there was a notable change in the adult's behavior, including increased proximity and touching. Oxytocin is more often described as a hormone that facilitates bonding and not one that directly increases care. Also, the mice were responding to pup calls and the rhesus macaque infants weren't necessarily providing cues. Similar to the explanation provided for the variation in estrogen and progesterone, rhesus macaques live in drastically different environments. Saltzman proposes that this is due to primates living socially and having a slower developmental trajectory, in which learning is more important.