According to a new study from Germany, the "love hormone" oxytocin may help maintain romantic relationships by prompting men to keep their distance from attractive women.
In the study, men in monogamous relationships who were given an oxytocin nasal spray stayed about four to six inches farther away from an attractive, woman they didn't know, compared with men in monogamous relationships who received a placebo. The oxytocin spray had no effect on the distance that single men chose to keep between themselves and the attractive woman. The results suggest the hormone promotes fidelity in humans, said study researcher Dr. René Hurlemann, of the University of Bonn. The findings agree with previous research conducted on prairie voles, which suggested the hormone plays a role in pair-bonding.
The study involved 57 heterosexual males, about half of whom were in monogamous relationships. After receiving either a dose of oxytocin or placebo, participants were introduced to a female experimenter who they later described as "attractive." During the encounter, the experimenter moved towards or away from the men, and they were asked to indicate when she was at an "ideal distance" away, as well as when she moved to a distance that felt "slightly uncomfortable."
The effect of oxytocin on the attached men was the same regardless of whether the female experimenter maintained eye contact, or averted her gaze. Oxytocin also had no effect on the men's attitude toward the female experimenter - whether men received the oxytocin or the placebo, they rated her as being equally attractive.
In this experiment, the men were asked to indicate when she was at an "ideal distance" away, as well as when she moved to a distance that felt "slightly uncomfortable". When they asked, they might be mindful of the procedure and the result of the experiment. In other words, since they knew this experiment was about the ideal distance between him and a woman, they might answered "ideally", probably not showing their "real ideal distance" especially when they are married. This might be the one reasons why men in monogamous relationships were affected by oxytocin, but the oxytocin spray had no effect on the distance of the single men.
Also the female experimenter's marital status or age might affect the men's attitude or answers. This experiment does not include how oxitocin act on the brain to affect the behavior. More research about the way oxytocin worka on the brain should be conducted.