Steven Pinker -- How the Mind Works - Hampshire High Italian ...

The Mind's Eye j 259Is a nose an object? Is a head one? Is it still one if it is attached to a body?What about a man on horseback? These questions show that the difficultiesin trying to formulate what should be recovered as a region from animage are so great as to amount almost to philosophical problems. Thereis really no answer to them—all these things can be an object if you wantto think of them that way, or they can be part of a larger object.A drop of Krazy Glue can turn two objects into one, but the visual systemhas no way of knowing that.We have, however, an almost palpable sense of surfaces and theboundaries between them. The most famous illusions in psychologycome from the brain's unflagging struggle to carve the visual field intosurfaces and to decide which is in front of the other. One example is the'Rubin face-vase, which flips between a goblet and a pair of profiles tetea-tete.The faces and vase cannot be seen at the same time (even if oneimagines two men holding up a goblet between their noses), andwhichever shape predominates "owns" the border as its demarcating line,relegating the other patch to an amorphous backdrop.DAnother is the Kanisza triangle, a stretch of nothingness that blocks out ashape as real as if it had inscribed it in ink.IIV ~7The faces, vase, and triangle are familiar objects, but the illusions do notdepend on their familiarity; meaningless blobs are just as compelling.I