Oxytocin heightens that warm and fuzzy bonding feeling, increasing sexual receptiveness and intimacy. Considered by many to be the key lubricant in the machinery of sex, oxytocin also increases the desire to be touched further, reinforcing the cycle of sex hormone escalation. Binghamton University psychology professor Diane Witt says that since the release of oxytocin can be classically conditioned, after repeatedly having sex with the same partner, just seeing that partner could release more oxytocin, making you want to be with that person all the more.

Research has shown that women who were currently involved in a committed relationship experienced greater oxytocin swells in response to positive emotions than single women, leading researchers to speculate that a close, regular relationship may influence the responsiveness of the hormone.