It’s an illusion that dates back to Roman magicians, but the “cups and balls” trick continues to awe: three overturned cups, three balls and a magician that seems to make the balls move through one ...

Just as our visual system strains to see the vase and the two faces at once, we struggle to conceive of a motion that has a dual motivation: to put and to fetch. A paper by Van de Cruys, Wagemans and ...