Board Thread:Questions and Answers/@comment-24826159-20140416214618/@comment-8986886-20140425105945

@Blazenite104, regarding Hollow intelligence.

I remember the individual Hollows as cunning creatures, who use reason, and even speech to lure their prey, while the Gillian are mindless beasts, because no individual has managed to take control yet.

What we know about Hollows is that they're drawn to, and have an instictive urge to attack, humans. Especially humans they had a strong connection to in life, as well as those who possess a fair amount of Reiryoku. This fits the description of pretty much every Hollow that we've seen so far, with the exception of the small lizard-like Hollow, Yammy's pet dog, and some of Aizen's Arrancar.