If retired Army Gen. David H. Petraeus had gotten an occasional dose of supplemental oxytocin, a brain chemical known to promote trust and bonding, he might still be director of the Central Intelligence Agency, new research suggests.

A study published Tuesday in the Journal of Neuroscience has uncovered a surprising new property of oxytocin, finding that when men in monogamous relationships got a sniff of the stuff, they subsequently put a little extra space between themselves and an attractive woman they’d just met.

Oxytocin didn’t have the same effect on single heterosexual men, who comfortably parked themselves between 21 and 24 inches from the comely female stranger. The men who declared themselves in “stable, monogamous” relationships and got a dose of the hormone chose to stand, on average, about 6 1/2 inches farther away.

When researchers conducted the experiment with a placebo, they found no differences in the distance that attached and unattached men maintained from a woman they had just met.

Even when an attractive woman was portrayed only in a photograph, the monogamous men who received oxytocin put a bit more distance between themselves and her likeness.

The latest findings suggest that oxytocin, which floods the body in response to orgasm, early romance, breast-feeding and childbirth, may act more subtly in humans than has been widely understood.

A mounting body of recent research suggests that boosting oxytocin in the human brain will indiscriminately promote trusting, friendly behavior. Research on female prairie voles has suggested the chemical might play some role in pair-bonding, and in humans playing games of risk and power, it increased empathy and trust in males and females alike. Injected into the cerebrospinal fluid of male rats, oxytocin causes spontaneous erections.

Accordingly, researchers examining oxytocin’s effects on people - including the authors of the latest study - assumed that men under its influence would draw closer to women, not farther away.

“This was quite surprising,” said Dr. Rene Hurlemann, a psychiatrist at the University of Bonn in Germany, who led the study.

At the same time, the new findings make evolutionary sense, Hurlemann added: As human societies evolved to give men an increasing role in safeguarding and supporting their mates and offspring, it appears that oxytocin may have taken on a more discriminating role in human interaction by favoring staying over straying behavior among men who’ve already found a mate.