Thanks, Lavinia! Sounds like your cats are seeing tiny critters if they are chattering at them. When our kitties see ghosts, not only do they stare at what looks like nothing to us, but follow them with the eyes, will look over and under the counter at them, and walk around the edge of the table, counter or bed while looking at something we can't see but they obvious can. One time Stretch was staring at something in the fully lighted hall, when nothing was there that we could see. As each cat walked into the room, they seemed to see the apparition in their peripheral vision, stopped, looked, then stood and stared into the hallway — soon we had five cats watching something in the hall that we couldn't see. It's a little eerie.