Folk art. We actually have a cat (Prissy) who does this. She's figured out that by hanging on the window screens and the door screen, she can see inside to see what's going on, figure out where her humans are, and be visible (especially if she howls !) to request entrance to the house. Training her otherwise is, of course, hopeless, so we've given up and installed heavy duty metal screens everywhere on the first floor to accomadate our little "feline spiderwoman". Private collection.