How autonomous/intelligent are individual undead?

[Tzaot]

In some pieces of asian mythology, there are two sorts of spirits in a body: The mind and the strenght/movement. While the mind is gone, the movementenergyhexmotaix can remain. Or something like that. Sadly I can't provide any source other than the anime Inu Yasha in which pretty brain-dead undead were risen in that way, while there were also "sentient" undead who had a more tragical backgroundstory and kept living by feeding on the souls of dead people or by holding shards of a certain powerfull artefact, that basically was made of compressed souls too.