FINDING female students not on the Pill has proved too challenging for North-East researchers.

A study by Northumbria University into male attractiveness ran into a serious problem.

They found it impossible to find enough women who were not taking the contraceptive Pill.

In desperation, they had to turn to colleagues in Austria to recruit all the women they needed.

Nick Neave, an evolutionary psychologist at the university, in Newcastle, said there was a suspicion the pill distorts the way in which women perceive men.

He said: "We tried to do an experiment with women who are not on the Pill, but we had major problems."

Northumbria University managed to recruit 20 women before appealing to colleagues in Austria to find more volunteers not on the Pill.

Mr Neave said: "We decided to transfer some work to Austria. It seems that most of their students are not on the Pill. The Pill makes your body think you are pregnant, and women seem to have different preferences when they are on the Pill."

The research was looking at factors that make men attractive to women. As part of experiments by the university's evolutionary psychology department, a researcher is looking at how male voices are perceived by women.

Mr Neave said: "We have also measured gay male voices. Women seem to be able to tell straight away if someone is gay from the voice.

"The voice might be something which signifies your hormonal status."

There was another surprising correlation between voices and appearances.

"If people listen to voices and then show them a row of photographs, they can often match the voice to the face.

"It seems that people with attractive voices seem to have attractive faces as well," Mr Neave said.