{"fact":"While crows can usually follow a treat being hidden, some struggle with more complex hiding tricks like rotating containers.","context":"They mastered visible rotational displacements consistently, but failed at more complex invisible rotational displacements.","source":"Almut Hoffmann; Vanessa Rüttler; Andreas Nieder, Ontogeny of object permanence and object tracking in the carrion crow, Corvus corone, 10.1016/j.anbehav.2011.05.012","index":177}