My cat, Random Numbers, is very attuned to her surroundings. One of her most interesting quirks is that she listens carefully for the sound of the latch's *click* whenever a door is swung shut. If she hears hinges squeak or the door hit the jamb and there's no sound of the latch engaging, she will be there within moments, reaching under the door with her paw and pulling it open to venture into The Place With The Old Cats And Soft Food or The Forbidden Basement Of Mysteries.
I had hypothesized that it was the sound of the latch that brought her over to investigate, and tested that hypothesis this morning while stepping through the "cat lock" into the dining room: I swung the door to, but left my hand on the knob and didn't engage the latch. As if on cue, she hopped off the futon in the living room and started strolling nonchalantly my way and then I pulled it 'til it clicked. Her ears twitched at the sound, and she immediately stopped in her tracks, looked over at me, and then ambled off in another direction.
Mm-hm. I'd wondered how she always seemed to sense when those doors weren't latched almost immediately. Now I know, and knowing is half the battle.