British researchers asked 30 men to listen to recordings made by four women aged around 25 who said the phrase, 'I really like you.' The male volunteers were asked to rate the women for attractiveness purely on the basis of the sound of their voice. They were shown no pictures.

When the pitch of the woman's voice was slightly raised by increasing the playback speed, the attractiveness rating increased - a finding in line with the previous research which suggests that higher voice tones are associated with youth and fertility in women.

The higher the pitch, the more the men liked it, even when the women's voices were tuned higher than average.

But when men listened to the same women saying the phrase 'I don't really like you,' they downgraded the attractiveness of the voice, regardless of the pitch.

And when the offending phrase was played backwards - leaving just the quality of the voice to be judged - the attractiveness rating once again increased.

The authors suggest that a clear verbal cue is one of the basket of signals that women can send to get a man to act on his impulses. Other cues include a smile, an eye-to-eye look and a pleased expression.

In other words, beauty by itself is not enough for a man.

Benedict Jones, lead author of the study and a professor at the University of Aberdeen in Scotland, suggests that the male need for clarity is a residual evolutionary trait.

In the mating business, ignoring subtle signals that one is not wanted could be a waste of precious time and energy or worse, he says.

'(The) mating effort is a finite resource,' notes Jones.

The study appears in Biology Letters, a journal published by the Royal Society, Britain's de-facto academy of sciences. -- AFP