chickens are already so witless that if you cut their heads off, they don't get any dumber.
It's a good link, but there is no call to say this. Chickens are not particularly stupid, have a reasonably advanced social hierarchy and can be trained.
I sometimes suspect my family's chickens are smarter than our cat. Bird's brains are organized differently, and while I haven't studies it or even though about it all that deeply so I could be dead wrong, birds seem vastly better at things humans tend to associate with smartness (presumably the things there is the most variation in between humans) than mammals relative to their total intelligence.
http://www.smbc-comics.com/index.php?db=comics&id=2393#comic