[心智探奇.史蒂芬·品克].pdf

d How rHE MrND woRKS I Each number representsthe brightnessof one of the millions of tiny patches making up the visual field. The smaller numbers come from darker patches,the larger numbers from brighter patches.The numbers shown in the array arethe actual signalscoming from an electronic cam- era trained on a personshand, though they could just as well be the fir- ing ratesof some of the nerve fibers coming from the eye to the brain as a person looksat a hand. For a robot brain--or a human brain-to recog- nize objectsand not bump into them, it must crunch these numbers and guesswhat kinds of objects in the world reflected the light that gaverise to them. The problem is humblingly difficult. First, a visual systemmust locatewhere an object ends and the back- drop begins. But the world is not a coloring book, with black outlines around solid regions.The world as it is projected into our eyesis a mosaic of tiny shadedpatches.Perhaps, one could guess,the visual brain looksfor regionswhere a quilt of large numbers (a brighter region) aburs a quilt of small numbers (a darker region). You can discem such a boundary in the squareof numbers; it runs diagonallyfrom the top right to the bottom cen- ter. Most of the time, unfortunately, you would not havefound the edge of an object, where it givesway to empty space.The juxtaposition of largeand small numberscould havecome from many distinct arrangements of mat- ter. This drawing, devisedby the psychologisrs PawanSinha and Edward Adelson, appearsto show a ring of light gray and dark gay tiles. SnndadEqutpnent I t In fact, it is a rectangularcutout in a black cover through which you