Some kitties are mentally challenged for sure. One of my sister's cats had a head shaped like a lemon, and she never learned to use the kitty door. Poor little thing just sat by the flap, and when another cat went thru, she squeezed in along side. My sister has her cats on twenty acres and has Anatolian Shepherds to protect them. Lucky cats can wander in and out of the house and barn whenever they want during the day. At night everybody comes inside, otherwise the Anatolians serenade the countryside, ha-ha!