In the largest study of its kind Dr Michael Lewis of Cardiff University's School of Psychology, collected a random sample of 1205 black, white, and mixed-race faces.

Each face was then rated for their perceived attractiveness to others -- with mixed-race faces, on average, being perceived as being more attractive.

Dr Lewis, who will present his findings to the British Psychological Society's annual meeting (April 14) said: "Previous, small scale, studies have suggested that people of mixed race are perceived as being more attractive than non-mixed-race people. This study was an attempt to put this to the wider test.

"A random sample of black, white, and mixed-race faces was collected and rated for their perceived attractiveness. There was a small but highly significant effect, with mixed-race faces, on average, being perceived as more attractive."

The study could also have wider implications than just attractiveness.

First established by Darwin in 1876, heterosis (or hybrid vigour) is a biological phenomenon that predicts that cross-breeding leads to offspring that are genetically fitter than their parents.

As heterosis is considered to be a universal biological effect, it is possible that humans are also subject to its influence and helps explain why mixed-race people appear more attractive.

Dr Lewis added: "The results appear to confirm that people whose genetic backgrounds are more diverse are, on average, perceived as more attractive than those whose backgrounds are less diverse. This can be taken as evidence for heterosis among human population groups.

"There is evidence, albeit anecdotal, that the impact of heterosis goes beyond just attractiveness. This comes from the observation that, although mixed-race people make up a small proportion of the population, they are over-represented at the top level of a number of meritocratic professions like acting with Halle Berry, Formula 1 racing with Lewis Hamilton; and, of course, politics with Barack Obama."