In a randomized double-blind placebo-controlled trial on 18 adult male volunteers, as measured by positron emission tomography (PET),  subjects received a nasal oxytocin stimulus and then rated unfamiliar female faces as more attractive. (Oxytocin is a neuropeptide that is involved with social approach including perception of faces.)  Results showed an absence of oxytocin effects on dopamine release and receptors in brain reward centers; however there was increased activity of the right prefrontal and superior parietal gyrus.

So what does this mean?  First, let’s look at the prefrontal gyrus. It carries out the executive function of the brain which involves personality expression, decision making, moderating social behavior, and working toward defined goals.  In simple terms this study indicates that the approach mechanism for men is located in our neural constructs and schemas rather than as a biological function related to the drive and hormonal system. This is in sharp contrast to the animal kingdom where mating practices are instinctual and biologically driven.  Perhaps, in the evolutionary process, hormonal and pheromonal factors have become secondary, whereas the cognitive factors and the reinforcement processes (or reward systems) have become predominant.

In a follow-up study, 19 homosexual and 18 heterosexual men were again administered oxytocin and then rated trustworthiness, attractiveness and approachability for male and female faces. Heterosexual men showed a decrease in ratings of trustworthiness for angry female faces; however, homosexual men also showed increased ratings of attractiveness and approachability for male faces regardless of the facial expression, as well as ratings of approachability for happy female faces.  These results appear to indicate that gay men display higher sensitivity to oxytocin’s enhancing impact on social approach tendencies than heterosexual men, escepially when it comes to attraction to men. This suggests that heterosexual men seem to use the executive function of the brain whereas gay men rely more on the oxytocin-dopamine pleasure seeking drive system.  In lay man’s term, heterosexual men seem to use the executive function of the brain in their head whereas gay men use the brain in their penis when it comes to desires to approach potential male sexual partners.

There is one other subtlety that we can glean from this study. Gay men appear to approach female faces that appear to be welcoming rather that angry under oxytocin enhancement, which may suggest that this arousal may be for warmth and non-sexual connection with women, perhaps indicating a desire for a sharing of the feminine side of their soul.  This leads to an interesting possibility for bisexual men. As bisexual men we appear to have a hormonal drive base when it comes to relationships with men, but a hormonal drive plus executive function when it comes to women. This means that our relationships with women may be very complex with multiple drives for social connection combined with sexual attraction. In other words we seek intimacy rather that eroticism.

Thienel et al, Oxytocin’s impact on Social Face Processing is Stronger in Homosexual than Heterosexual men; 2013 (http://dx.doi.org/10.1016/j.psyneuen.2013.09.013)