A 'golden ratio' for female facial beauty has been discovered in a new study by researchers from the University of California, San Diego and the University of Toronto.
They have found that the distance between a woman's eyes and the distance between her eyes and her mouth are key factors in determining how attractive she is to others.
For the study, Pamela Pallett and Stephen Link of UC San Diego and Kang Lee of the University of Toronto tested the existence of an ideal facial feature arrangement.
They successfully identified the optimal relation between the eyes, the mouth and the edge of the face for individual beauty.
In four separate experiments, the researchers asked university students to make paired comparisons of attractiveness between female faces with identical facial features but different eye-mouth distances and different distances between the eyes.
They found two 'golden ratios,' one for length and one for width. Female faces were judged more attractive when the vertical distance between their eyes and the mouth was approximately 36 percent of the face's length, and the horizontal distance between their eyes was approximately 46 percent of the face's width.
These proportions correspond with those of an average face.
"People have tried and failed to find these ratios since antiquity. The ancient Greeks found what they believed was a 'golden ratio' - also known as 'phi' or the 'divine proportion' - and used it in their architecture and art," Pallett said.
"Some even suggest that Leonardo Da Vinci used the golden ratio when painting his 'Mona Lisa.' But there was never any proof that the golden ratio was special. As it turns out, it isn't.
"Instead of phi, we showed that average distances between the eyes, mouth and face contour form the true golden ratios," Pallett added.
Lee said: "We already know that different facial features make a female face attractive - large eyes, for example, or full lips."
"Our study conclusively proves that the structure of faces - the relation between our face contour and the eyes, mouth and nose - also contributes to our perception of facial attractiveness. Our finding also explains why sometimes an attractive person looks unattractive or vice versa after a haircut, because hairdos change the ratios," Lee added.