Actually, it’s around 5 seconds. More or less.
After being beheaded, your blood supply to the brain cuts off, which will then lead to being brain dead, which means your ability to think stops.
A famous case I read about ages ago was of Queen Anne Boleyn, who was the second wife of King Henry VIII (the dude who beheaded 2846729348 wives because they couldn’t bear sons). When she was beheaded, the executioner picked up her head she appeared to blink for a few seconds. Her lips quivered and twitched as well. But apparently this only happened because of reflex muscles twitching after the blood supply to the brain has been cut off.
True facts.
I think.
