A hormone normally released during childbirth and linked to sexual pleasure and bonding also seems to help men to recognize faces, researchers have found.

"Recognizing a familiar face is a crucial feature of successful social interaction in humans," said Peter Klaver of the University of Zurich, the senior author of the study.

"In this study, we investigated for the first time the systematic effect of oxytocin on social memory in humans."

Klaver and his colleagues gave 44 men a nasal spray containing the hormone oxytocin or a placebo. Participants were then shown images of faces and inanimate objects such as houses and sculptures.

The next day, participants were tested on their ability to recognize the images and distinguish them from new images.

Volunteers given the oxytocin spray recognized the faces more accurately than those in the placebo group. But there was no difference in terms of recognizing non-social images, which suggests oxytocin acts specifically on improving social memory, the team reported in Wednesday's issue of the Journal of Neuroscience.

Further tests showed the hormone made it less likely for people to mistakenly characterize unfamiliar faces as familiar, the researchers said.

"The study highlights the parallels in social information processing in mice and man and adds further support to the notion that oxytocin plays a critical role," said Larry Young, an expert on oxytocin who did not participate in Klaver's study.

"This has important implications for disorders such as autism, where social information processing is clearly impaired," he added.

Oxytocin is also a critical hormone for mice. The animals use it to recognize and distinguish other mice.

With files from Reuters