For the study, the scientists trained four hens to react to photos of an average female face but not an average male face, and vice versa for their male counterparts. Then, the chickens were shown pictures of faces with exaggeratedly masculine and feminine traits. As a result, the chickens pecked more at screens that showed symmetrical faces – revealing the same preferences for faces that humans have. These results suggest, that our natural inclination towards symmetry is rooted in the nervous system, contrary to the previous belief that it is so because of our cultural influences.