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The volunteer's face (left) was combined with a subject's face (centre) to produce a composite with similar features (right)

However, psychologist Dr Lisa DeBruine found a facial resemblance is not a turn-on when we are looking for a partner.

She believes we may have evolved to prefer the company of people who remind us of family - but have a biological block to prevent incest.

The study is published in the Journal of the Royal Society.

The researchers showed volunteers male and female faces that had been computer-manipulated to produce a 'family resemblance'.

Men liked other men's faces that resembled their own and women liked other women's faces that resembled their own.

However, a facial resemblance did not influence attraction to opposite-sex faces.

Trust

Dr DeBruine, of McMaster University, Canada, said previous research had shown that people were more likely to trust others who looked like them.

In one of her previous studies she found people playing a two-person monetary investment game over the internet while viewing a picture of the "second player" were more likely to trust this player if the picture was digitally morphed to resemble them.

She believes it may be possible that we are evolved to place greater trust, and to have greater affection for, people who look as though they may be related to us because the chances are higher that they share the same genes as us.

By forging a bond in this way, it could help these people to thrive, and thus, in evolutionary terms, to pass their genes down to the next generation.

Professor David Perrett, of the Perception Lab at St Andrew's University, told 成人论坛 News Online: "It is likely that people who look similar to ourselves share our genes, and it makes sense to help the cause of these individuals because, in effect, we are helping our own genes."

However, he said it was important that individuals are not instinctively attracted sexually to people who look like them as inbreeding can increase the risk of disease and genetic disorder significantly.

"We should trust people who share our genes, build friendships with them, but not go to bed with them," he said.