> Cats can vary wildly. One of my cats seems dumb as a box of rocks and haven't even grasped the idea of object permanence

Similarly I've seen cats have one of two reactions to a mirror: ignoring it entirely or actually using it by e.g. looking me in the eyes and meowing at me through it. While I've not witnessed it personally on the internet there's also tons of videos of cats freaking out and trying to fight the other cat in the mirror.

This supports the idea that the gamut of intelligence in cats is quite wide.