A brain chemical dubbed "the hormone of love" could encourage wallflowers to become more outgoing at social gatherings, a study shows.

Now researchers have found it improves the social skills of the shy -- but has little effect on those who are naturally confident.

This involved watching others discussing emotional moments in their lives, then rating how they felt those people were feeling.

The scientists, whose research is published in Psychological Science, also measured the participants' social competency, using a test known as AQ which is usually used in autistic patients.

The finding could have implications for those with severe social deficiencies, often apparent in conditions like autism.

They conducted a test of 27 healthy adult men, giving them the hormone or a placebo via a nasal spray and then asking them to perform an "empathetic accuracy task".

The more socially comfortable participants performed well on the empathetic accuracy task regardless of whether they were on oxytocin or placebo,

but less socially proficient participants performed significantly better on oxytocin, with their empathetic accuracy performance identical to that of the socially proficient participants.

Prof Jennifer Bartz, of the Mount Sinai School of Medicine, said: "Oxytocin is widely believed to make all people more empathic and understanding of others. Our study contradicts that. Instead, oxytocin appears to be helpful only for those who are less socially proficient. Our data show that oxytocin selectively improves social cognition in people who are less socially proficient, but had little impact on more socially proficient individuals."