Scientists took the data and applied an algorithm involving 234 measurements between facial features, including the distances between lips and chin, the forehead and the eyes, or between the eyes. Essentially, they trained a computer to determine, for each individual face, the most attractive set of distances and then choose the ideal closest to the original face. Unlike other research with formulas for facial attractiveness, this program does not produce one ideal for a feature, say a certain eye width or chin length.

They ran the photographs of 92 women and 33 men through the engine, creating before and after shots - essentially, a computer-generated version of hot or not. Changes were made only to the geometry of the faces; unlike the digital retouching done for fashion magazines, wrinkles were not smoothed and hair colour was not changed. The research was revealed at Siggraph, an annual conference on computer graphics, held in August. Studies have shown that there is surprising agreement about what makes a face attractive. Symmetry is at the core, along with youthfulness; the beauty merits of clarity or smoothness of skin and vivid colour, say, in the eyes and hair. There is little dissent among people of different cultures, ethnicities, races, ages and gender. Yet this software program raises what psychologists, philosophers and feminists say are disturbing questions.

To what extent is beauty quantifiable? Does a supposedly scientific definition merely reflect the ideal of the moment, built from pop culture? Lois Banner, a historian who has studied changing beauty standards, says scientific efforts to define attractiveness are fraught with difficulty. "They are never going to locate it on a gene. They are never going to get away from the cultural influence."

Tommer Leyvand, who helped develop the "beautification" software at Tel Aviv University and who works for Microsoft, said the goal was to alter a face according to agreed standards of attractiveness, while producing a result that left the face recognisable, rather than the product of surgery or digital retouching. "This tool shows in the most simple fashion how easy it is to manipulate photographs and make people more attractive," Leyvand said. "But the difference is so subtle that it just shows how insignificant it is. We're talking about a few inches maybe and a slightly changed perception." For most faces, the software made subtle changes, with the person's essence and character largely intact. However the changes appear more striking among people from non-Caucasian groups because researchers have yet to create a program designed with "a beauty estimator" for non-white racial and ethnic groups.

While psychological studies over the past few decades suggest that perceptions of beauty and attractiveness tend to be universal, critics of that work say it is debatable whether a person's beauty is enhanced by such changes. Character can be lost. Blandness can set in. The quirky may become plain. When Leyvand put a photograph of Brigitte Bardot through his program, her full and puckered lips were deflated, and the famed beauty seemed less striking - less like herself.

(By contrast, the before and after shots of the actor James Franco were almost indistinguishable, suggesting his handsome face is perfect.) After viewing the before and after photographs in Leyvand's research paper, Banner, a professor of history at the University of Southern California, said the original faces were more attractive. "Irregular beauty is the real beauty," he said, adding that such attempts to measure beauty are driven by sameness, making everyone look alike. The New York Times