A dear old friend of mine (and possibly the smartest person I've ever known) who happens to be neurologist and highly-respected researcher said about this image, "one for perception textbooks ... vivid examples of amodal completion of near-foreground plants occluded by fence. Why don't we find completions to the horse's head? Maybe it's a unicorn!"
I'm not completely sure about "amodal completion," but I'm damned sure that this fellow (or gal or gelding???) is no unicorn. In any case, thank you Dr. S.