Do better-looking men produce better-quality sperm? Do those with symmetrical features make better lovers - and, if so, is it because they are likely to get more practice?

Can women spot from other women's faces whether they are more interested in long-term relationships or casual sex, and do they find different men attractive at different phases of the menstrual cycle?

In every case, claims a book published this week, the answer seems to be yes.

David Perrett, author of In Your Face: The New Science of Human Attraction, is professor of psychology and head of the Perception Lab at the University of St Andrews.

³ÉÈËVRÊÓƵ

The lab pioneered the graphic manipulation of faces, and first came to fame when it produced an image of former prime minister Margaret Thatcher morphing into Michael Heseltine.

The basic technique is pretty straightforward: ask people to look at a number of faces and say which they find most attractive; use statistics or speculation to postulate which cues they are responding to; and then graphically modify the cues to see how people respond to the changes.

³ÉÈËVRÊÓƵ

Idiosyncrasies can be eliminated, moles removed, shoulders broadened and hair made more lustrous. If the researchers' theory is correct, accentuating the positive - until the faces start to look freakish - will increase the attractiveness rating. The results, as set out in Professor Perrett's book, are often startling.

"Aesthetics used to be the preserve of philosophy departments, and not considered amenable to objective scientific analysis," he said.

"Our work took off when we began to realise that we could use graphic means to change identities or other aspects of faces."

In various ways, he argued, "the interplay between looks and personality is much more intricate than we thought". Our looks affect the way we are treated, which in turn influences our attitude to the world and that shows in our faces.

³ÉÈËVRÊÓƵ

Many people, Professor Perrett said, are "good at spotting others' personality from their faces. Most of us do better than chance, although we are not brilliant at it and often overgeneralise from our experience. Those with rather Machiavellian personalities tend to be best at it."

Not everybody, he admitted, feels entirely comfortable with his sort of research.

"We don't like everything to be reduced to biological determinism, and it can lead to a strong backlash. But that's throwing out the baby with the bathwater.

"We have to acknowledge the role of biology. But that is not incompatible with the influence of family, friends and culture.

³ÉÈËVRÊÓƵ

"Judgements of attractiveness are unique to individuals, although some factors are also universal. I don't see those two perspectives as contradictory," he said.

matthew.reisz@tsleducation.com.