If you sit down next to a cat, and throw your arm over the back of the sofa while someone reaches over from behind and starts to pet the cat, and then after a little bit you stand up and leave while the phantom arm is still petting the cat, the cat understands that something really freaky is happening, gets scared, and runs away.

I would have thought they’d be happy that whatever weird thing is happening is petting them, but apparently not. An arm with no human is alarming and bad. I think it’s cool that their mental model is that similar to ours.