Totally agree they are way more intelligent than we give them credit for. My cat story, apologies for the length...
The setup:
Friend has a small bungalow with two rescue cats that never go outdoors. One was from animal cops, rescued from a house with dozens of cats. I've watched the show, cats running everywhere. Cat was totally skittish around people. Usually kept to herself. Never let me pet her.
Anyhow one day a large mattress gets delivered and two really big guys take it up to the attic. Lots of commotion in the small cramped house.
About a half an hour after they leave we notice that the cat is missing. My friend thinks she must have freaked out, commotion probably reminded her of the rescue operation. We think the cat bolted outside as the front door was held open for a while. Anyhow my friend is in a panic, searching everywhere, outside, around the house, under the porch, neighbors yards, etc.
About half an hour later I give up and tell her that if the cat wants to come home she will in her own time.
Now the story...
I go inside and sit back down on the couch in the living room.
After a few minutes I notice her other cat (the friendly one) is standing in the arch between the rooms and meowing. Staring at me and just meowing, pretty verbal for a cat. Not sure what she wants. Try to get her to come to me but she won't.
Finally I go to get up but as I move towards the cat she moves away into the next room. sigh I sit back down.
The cat soon comes back into the archway and starts meowing again. I get up again. She moves away again. :/ I sit back down.
She comes back a third time, meowing. At this point I know something is up.
This time I get up and walk to where she was and stand there. The cat moved into the dining room, standing in the archway to the kitchen, stares at me and continues to meow.
I move towards her into the kitchen and stand there, she moves to the top of the basement stairs, stares at me and meows.
I move to the top of the stairs, she goes down the stairs, sits at the bottom, stares at me and meows.
I go down the stairs, she moves into the utility room, stares, meows.
I move into the utility room, she moves to the wash tub and stares at the washing machine, meowing
I look behind the washing machine, and I'll be damned the missing cat is huddled up in a ball hiding there.
Mind blown... that cat knew we were in a panic looking for the other cat, knew where it was, and was determined to communicate her location to us.
Judging from the results I'd say she was pretty effective in her communications. How frustrating it must have been for her not to be able to communicate in any other way!
I have a whole new respect for cats now.