Perfect legs (Nicole's got them. So has little Tom)

She is one of the most successful and highest-earning actresses in the world. Now scientists think Nicole Kidman is physically perfect - well, as far as her legs are concerned.

According to new research, the perfect shape for a woman is legs that are 1.4 times the length of her upper body, as in Ms Kidman's case. But in men, shorter legs, the same length as the torso, are the most appealing. Tom Cruise, while shorter than his ex-wife, actually enjoys just such proportions.

Researchers believe the attraction for long legs in women and shorter versions in men may have evolved for different reasons. Long legs may be a sign of good health and good childbearing capabilities in women, while short legs may make men looked more muscular.

Although there has been some research on the attractiveness of height, the new study by psychologists from Liverpool University and University College London has homed in on the ratio of leg and body length.

"A relatively unexplored approach is to consider the different components of height separately. One such component, recognised in clinical research but neglected otherwise, is the leg-to-body ratio," they say.

On average, legs make up half of adult height, but there are wide individual differences, and women tend to have a higher leg-to-body rations (LBRs).

In the study, reported in the journal Body Image, the researchers had volunteers rate male and female drawings with different LBRs.

"The results of this investigation are consistent with the idea that the LBR plays a role in judgements of male and female physical attractiveness. Over all, both male and female participants showed a preference for higher LBRs in women and lower LBRs in men,'' say the researchers.

Just why long legs are attractive in women but not in men is unclear. Some research, say the psychologists, suggests that tall women have wider pelvises than shorter women, allowing easier births and higher birthweight babies.

Other work shows that long legs signify good health: "Interruption of growth results in a relatively long torso and short legs. If the rate of growth is slowed down due to nutritional deficiencies or psychological stress, the adult will have shorter legs relative to the trunk." Longer relative leg length is also associated with a reduced risk of heart disease, cancer and diabetes, lower blood pressure, better cardiovascular profiles, lower adult mortality and reduced risk of cancer.

That may explain the attraction for long-legged women, but not the appeal of shorter legs in men: "If you have shorter legs in comparison with your torso length, you appear to have a bigger torso, which may make you appear more muscular," says Dr Viren Swami, who led the study.