So a brain stem is clearly enough to keep a chicken alive, but do you think Mike was really conscious at all (by the normal standards of chicken consciousness)? Or was he essentially a chicken zombie?
That's a tough one. I raised chickens (laying hens) for several years in my teens. I'm not sure that chickens have distinct personalities, although I'm sure these urban backyard crunchy chicken people would disagree. They will eat each other given half a chance - if one hen got a scratch or cut, the others would peck it to death in a day or so.
Even given that, I'd go with the chicken zombie.
I also grew up around chickens. I would say there is definitely some aspect of personality, but they are also exceedingly dumb compared to similar farm animals
This holiday season, give thanks that you and your loved ones are not headless chickens.
There was a 2-headed calf here in Idaho. https://www.roadsideamerica.com/tip/15634
Came up on Junior Taskmaster today … https://youtu.be/Dkdcggh1SbU