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.
Nipple stimulation
Oxytocin is linked to sexual arousal and pair bonding, but researchers are divided on whether breastfeeding commonly incites sexual feelings. Nipple erection may also result during sexual arousal, or during breastfeeding; both are caused by the release of oxytocin. Nipple erection is due to the contraction of smooth muscle under the control of the autonomic nervous system, and is a product of the pilomotor reflex which causes goose bumps. A survey in 2006 found that sexual arousal in about 82% of young females and 52% of young males occurs or is enhanced by direct stimulation of nipples, with only 7–8% reporting that it decreased their arousal.