We have 4 cats, and this evening one of them has been ripping up the carpet trying to get out of our bedroom. I could hear him, and thought the bedroom door must have got shut by accident because the door opens outwards. No, he just seemed to have got confused that he didn't have to pull the door towards him with his paw (and he is useless at getting into the room from the hall too).
This follows on from each of the cats getting a microchip cat feeder over the last couple of years. The first cat took about 6 months to use it regularly of her own accord (there was a bit of active resistance as well as genuine confusion and fear of the noises it made). The second cat was up and running in about 48 hours. Cats three and four got theirs in the Black Friday sales this year. Cat three had the hang of it in about 12 hours. Cat four is the boy getting stuck in the open bedroom - still having to be guided to use it!
On another note, cat one is still confused by the cat flap - 4 years after being introduced to the concept. I hear her trying to claw the flap towards her rather than just pushing her head through - on both sides of the door :-D
Do your cats demonstrate different levels of intelligence?