Chicken who keep running around after their heads have been cut off are a common story told by people who have grown up on farms, including my mom. I always assumed that this headless-but-alive state lasts a few seconds at best, but in the 1940s a chicken called Mike stayed alive for 18 months after it was beheaded.
That a chicken can get by without its head suggests that the head and the mind it held weren’t great to start with. Here is Werner Herzog’s low opinion on chicken intelligence.
Nehaveigur 