A hormone thought to encourage bonding between mothers and their babies may foster social behavior in some adults with autism, French researchers said on Monday.

They found patients who inhaled the hormone oxytocin paid more attention to expressions when looking at pictures of faces and were more likely to understand social cues in a game simulation, the researchers said in the journal Proceedings of the National Academy of Sciences.

Angela Sirigu of the Center of Cognitive Neuroscience in Lyon, who led the study, said the hormone has a therapeutic potential in adults as well as in children with autism.

"For instance, if oxytocin is administered early when the diagnosis is made, we can perhaps change very early the impaired social development of autistic patients," Sirigu said in an email.

Sirigu said the study focused on oxytocin because it was known to help breast-feeding mothers bond with their infants and because earlier research has shown that some children with autism have low levels of the hormone.

People with Asperger's syndrome and other autism spectrum disorders often have problems with social interaction.

Sirigu said oxytocin could help autism patients who have normal intellectual functions and fairly good language abilities because it improves eye contact.

"Eye contact can be considered the first step of social approach," Sirigu said. But people with autism often avoid looking at others.

"In our study we show that oxytocin enhances eye contact because patients spent more time looking at the eyes," she said.

She said the hormone also improves the ability of people with autism to understand how other people respond to them, and they can learn the appropriate response to others' behavior.

In their study, Sirigu and colleagues had 13 people with high-functioning autism spectrum disorders inhale oxytocin before taking part in two experiments.

The participants, 11 men and two women, had no medication two weeks before the study, which included a control group of an equal number of healthy men and women.

The researchers watched the patients' responses during a virtual ball tossing game to measure behavioral changes.

In a separate experiment, Sirigu's team measured how patients responded to facial expression when shown pictures of human faces.