It's been decades since Marilyn Monroe ruled the silver screen. But, according to a study, it seems gentlemen still prefer blondes.

Researchers found that men judge women with blonde hair to be ‘significantly’ younger and healthier-looking than brunettes.

And, falling to prey to old stereotypes, they also judged blonde women to be more promiscuous.

However, while this gave blondes the advantage when it comes to dating, brown-haired women have a slight advantage when it came to marriage – as they are judged to have greater ‘parenting potential’.

The study of 110 men, led by Augsburg University in Minnesota, follows previous research that blondes get more tips as waitresses in restaurants and are more likely to be offered help by men.

Psychologists showed the men computer-generated photographs of women with blonde, brown or black hair.

Researchers found the men rated women with lighter hair as being more attractive and having greater relationship potential than those with black hair. There was little difference between blondes and brunettes for these measures.

The men also judged the blonde women shown to them to be more promiscuous – with researchers suggesting this means they are more likely to pick them as dates.

But because of this men are more likely pick a brunette to be the mother of their child.

The study also found women with long hair are seen as less healthy and attractive, with women with medium-length hair judged to have better relationship potential.

In cavemen times, hair colour was seen as a good way to pick a potential partner.

Because our hair tends to darken with age, women with naturally lighter hair are younger and so were seen to be more fertile.

However the psychologists also suggested that men's preferences when it comes to judging if a woman is desirable may have been changed by decades in which blondes have been ‘vastly over-represented’ in the media.