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".