A hormone associated with emotional bonding promotes social behaviour in adults with autism, French researchers say.

Scientists at the Center of Cognitive Neuroscience in Lyon found that patients who inhaled the hormone oxytocin paid more attention to pictures of faces and were more likely to notice social cues when playing a game.

In the small study, Angela Sirigu and colleagues gave the hormone to 13 patients with Asperger's syndrome, considered to be a high-functioning autism spectrum disorder.

They then observed those patients and an equal number of other patients who didn't receive the treatment playing a virtual ball-passing game.

In another experiment, the researchers measured the patients' attentiveness to emotional expressions on pictures of human faces.

The patients who received the hormone showed more attention to the visual cues in the pictures of faces, and were more likely to understand the social cues in the game.

Sirigu said the study, published this week in the Proceedings of the National Academy of Sciences, merits future research on the possible benefits of the hormone in promoting social behaviour.

People with classical autism are often uncommunicative, while those with Asperger's are often very bright but have problems with social interaction.

Previous research has found that some children with autism are deficient in oxytocin, sometimes called the "love hormone."