As it turns out, relationships are indeed all about the chemistry.
New research has found that the so-called love hormone makes attached men stay away from other women.
Scientists already knew that oxytocin acts to bond mothers with their babies and romantic partners with each other. Previous research with prairie voles showed it to be key in keeping pairs monogamous.
In a new series of experiments, reported on LiveScience.com, men in relationships who inhaled an oxytocin nasal spray kept a greater distance from attractive women than single men did -- a distance about four to six inches greater, to be exact.
The dosed men did not expand their "personal bubble" in the presence of other men. They were also slower to react to images of beautiful women.
The study, by researchers at the University of Bonn in Germany, is published Wednesday in the Journal of Neuroscience.