I wonder what aspects of human beauty chickens are perceiving? Purely at a guess, I would say symmetry of features and signs of health/reproductive health. Given that they’re looking st faces, this seems most likely to me.

If chickens are anything like a neural network (and they kinda have to be at some level, perhaps a more complicated network than what we have in our computers now, but a learning discriminator network nonetheless) - it sounds like they would be reacting on the features which vary the most between male and female faces.

They have trained chickens to discern between male and female faces. It would be logical to assume that they have found features that allow them to put each sample on that one-dimensional scale, and then use those features. It would mean that a more "beautiful" face is the one that is most distinguished in it's features from the face of another sex.

This would be the most naive interpretation, but as always in nature, there can of course be layers of complexity on top of this.

I don’t think this is a good explanation. Having played with Poser [0] as a kid a lot, my intuition is that extreme feature parameter settings usually look rather disfigured and unattractive. The chicken brain more likely forms two clusters [1] (one for each sex) and responds more strongly the closer the sensory input is to either of the cluster means. Average faces tend to look attractive, e.g. [2].

Another, related explanation might be Occam’s razor (the preference for simple things [3]): Beautiful things are beautiful because they are simple. They require fewer bits to be represented and brains prefer such representations. This is a fact that possibly also explains intrinsic motivation and our interest in art and science [4].

Another explanation might be that chickens have evolved abilities to recognize symmetric body shapes and a uniform skin texture for their own intraspecies visual (sexual) attraction. Sexual attraction to symmetry likely mainly exists because asymmetry is reliable evidence that growth hormone signaling was not only out of tune in some regions of the body (e.g. the face), but throughout the entire system and this is the root cause of all kinds of diseases (e.g. faster wearing joints) [5].

[0] https://en.wikipedia.org/wiki/Poser

[1] https://www.facebook.com/nipsfoundation/videos/1555427447881...

[2] https://i.imgur.com/Xs4njxa.jpg

[3] https://en.wikipedia.org/wiki/Occam%27s_razor

[4] http://people.idsia.ch/~juergen/creativity.html

[5] http://www.aiai.ed.ac.uk/project/oplan/documents/1999/1999-M... (Entry "Section Sexual Attraction, Evolutionary Psychology of", p. 884. The entire entry is well worth reading.)

Chickens are nice, and usually more intelligent than what most people think, but the "attractive" people choice sounds a bit too much to be plausible. It could be that they like simmetry, but not necessarily a simmetric face is also "attractive".

Anecdotally however my father used to have one that not only recognized us (all people in the family) from a distance, she would also act as a guard dog if anyone else entered the court she lived in.

OT, and probably re-known, however here is the story of Mike, the headless chicken:

https://en.wikipedia.org/wiki/Mike_the_Headless_Chicken

There is also another point of view; the reason we have a concept of 'good looking' human faces to begin with is because, at some point, the human brain has to distinguish between looking at another ally (human) or a possible predator. So better looking people are just humans that look more.. human. It's not a stretch then for other animals such as chickens to also think this way, and they may get confused looking at less attractive human faces that resemble other predators that they are hard coded to run from.

A rising trend in many Asian cultures is to consider extremely feminine men as beautiful. In the history the beauty standards have also shifted several times.

Symmetry is explicitly mentioned in the original article and the study you're commenting on.