A scene from Gus Van Sant's Elephant. A study found that a whiff of the 'cuddle chemical' oxytocin made men rate their partners as being more attractive.

London - When a man tells his wife or girlfriend she looks nice, it’s his hormones talking, researchers say.

A study found that a whiff of the “cuddle chemical” oxytocin made men rate their partners as being more attractive.

However, the hormone, released when we hug or kiss, did not make work colleagues or strangers seem more beautiful.

Researchers from the University of Bonn in Germany said that oxytocin may play a key role in monogamy, a trait that is rare in other mammals. They showed 40 young men pictures of their partners.

They were asked how attractive they found the women after being given a placebo spray to sniff and a burst of oxytocin. Pictures of strangers and of long-term acquaintances, such as work colleagues were also shown.

Lead author Dirk Scheele said: “When the men received the oxytocin instead of placebo, the reward system in the brain was very active when viewing their partner and they perceived them as more attractive than other women. We did not detect this effect with pictures of long-standing acquaintances.”

Writing in the journal Proceedings of the National Academy of Sciences), the scientists said that the oxytocin released during close physical contact seems to boost monogamy by making a woman seem more attractive – but only when the two are in a loving relationship. The drop in oxytocin production found when a relationship ends could make the break-up harder to bear.

“The biological mechanism in a couple relationship is very similar to a drug. This could also explain why people fall into depression or deep mourning after a separation.” - Daily Mail