Averageness

In physical attractiveness studies, averageness describes the physical beauty that results from averaging the facial features of people of the same gender and approximately the same age. The majority of averageness studies have focused on photographic overlay studies of human faces, in which images are morphed together. The term "average" is used strictly to denote the technical definition of the mathematical mean. An averaged face is not unremarkable, but is, in fact, quite good looking. Nor is it typical in the sense of common or frequently occurring in the population, though it appears familiar, and is typical in the sense that it is a good example of a face that is representative of the category of faces.

A possible evolutionary explanation for averageness is koinophilia, in which sexually-reproducing animals seek mates with primarily average features, because extreme and uncommon features are likely to indicate disadvantageous mutations.

The effect was first described in 1878 by Francis Galton. He had devised a technique called composite photography, which he believed could be used to identify 'types' by appearance, which he hoped would aid medical diagnosis, and even criminology through the identification of typical criminal faces. Galton's hypothesis was that certain groups of people may have common facial characteristics. To test the hypothesis, he created photographic composite images of the faces of vegetarians and criminals to see if there was a typical facial appearance for each. Galton overlaid multiple images of faces onto a single photographic plate so that each individual face contributed roughly equally to a final composite face. The resultant "averaged" faces did little to allow the a priori identification of either criminals or vegetarians, failing Galton's hypothesis. However, unexpectedly Galton observed that the composite image was more attractive than the component faces. Galton published this finding in 1878, and also described his composite photography technique in detail in Inquiries in Human Faculty and its Development.

Similar observations were made in 1886 by Stoddard, who created composite faces of members of the National Academy of Sciences and graduating seniors of Smith College.

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