Here's an interesting little experiment. A group of chickens and a group of humans were asked to "rate" male or female faces based on beauty. The chickens agreed with the humans. But what does it mean?
The experiment began when a group of researchers recruited a group of trained lab chickens, who were savvy about experimental procedure (they wanted chickens who were familiar with experimental procedures so they wouldn't have to train a bunch of chicken newbs. They did stress, though, that none of the chickens had participated in facial recognition experiments before).
The training procedure involved a touch screen and two faces, which were digital composites. The male face was an average of 35 male faces; the female face was an average of 35 female faces. (You can see them on the picture below. They're marked with red lines.) The cocks were trained to peck at the female face and rewarded with food when they did, while the hens were trained to peck at the male face.
Then the testing started. Instead of just the two faces, the researchers saw how the chickens responded to each of the faces on the picture below. The average faces are marked. The face at the very center is the average of the average — the male and female faces blended together. As you move towards the edges of the continuum, those two average faces are digitally manipulated to look exaggeratedly male or female. Each of the faces were flashed on the screen, and the researchers recorded what the chickens pecked at. They also brought in a group of humans and had them rate each of the faces on how much they would like to go on a date with them. As you can see, the chickens and the humans agreed. They went for the exaggeratedly feminine, or masculine, faces. (The graph is a bit confusing. It doesn't show the response to the faces displayed on the continuum. The study notes, "Animal data are aligned so that face 3 is the unrewarded face, and face 5 is the rewarded one. For humans face 3 is the same sex average and face 5 is the opposite sex one.")
What does this tells us? The researchers believe that it shows that attractiveness isn't merely a social construct, but at least in part arises from the properties of the nervous system, properties that are evident even in chickens. Others disagree, and believe that the experiment merely shows that chickens can extrapolate from basic data. They can rate faces on a mental scale and know which is a step toward the image that will get them a mouthful of chicken feed, and which is a step away from the image that will get them their next meal. One critic suggests repeating the experiment with larger sets of pictures, and different training and testing pictures.
I'd be interested in what the limits of gender and attractiveness are for chickens, and what they are for humans. One of the major complaints people have about plastic surgery is that it emphasizes and emphasizes desirable traits until they become undesirable. People can look like cartoon versions of themselves. I'd like to see how chickens, and people, respond to faces with an ever-more-exaggerated set of features until women have giant blown-up lips and eyelashes, and men have little squinty eyes and jaws that can be used to accurately trace a right angle. Will the humans still find them attractive? Will the chickens?