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

262 I HOW THE MIND WORKSsays, "There's an edge here," what "here" means is the position of thatcell on the retina—say, dead straight ahead where you're looking. Thatwould be fine if you were a tree looking at another tree, but as soon assomething moves—your eyes, your head, your body, a sighted object—the information lurches to a new resting place in the array. Any partof the brain being guided by information in the array would find that itsinformation is now defunct. If your hand was being guided toward thecenter of the visual field because that spot had contained an apple,the hand would now be heading toward empty space. If yesterday youmemorized an image of your car as you were looking at its door handle,today the image would not match your view of the fender; the two viewswould barely overlap. You can't even make simple judgments like whethertwo lines are parallel; remember the converging railroad tracks.These problems make one long for a scale model in the head, but thatisn't what vision delivers. The key to using visual information is not toremold it but to access it properly, and that calls for a useful referenceframe or coordinate system. Reference frames are inextricable from thevery idea of location. How do you answer the question "Where is it?" Bynaming an object that the asker already knows—the frame of reference—anddescribing how far and in what direction the "it" is, relative tothe frame. A description in words like "next to the fridge," a streetaddress, compass directions, latitude and longitude, Global PositioningSystem satellite coordinates—they all indicate distance and directionrelative to a reference frame. Einstein built his theory of relativity byquestioning Newton's fictitious reference frame that was somehowanchored in empty space, independent of anything in it.The frame of reference packaged with the 2V2-D sketch is position onthe retina. Since the retinas constantly gyrate, it is as useless ds directionslike "Meet me next to the beige Pontiac that's stopped here at thelight." We need a reference frame that stays put as the eyes rock and roll.Suppose there is a circuit that can slide an invisible reference frame overthe visual field, like the crosshairs of a rifle sight sliding over a landscape.And suppose that any mechanism that scoops information out of thevisual field is locked onto positions defined by the rifle sight (for example,at the hair-crossing, two notches above them, or a notch to the left).Computer displays have a vaguely similar device, the cursor. The commandsthat read and write information do so relative to a special pointthat can be positioned at will over the screen, and when the material onthe screen scrolls around, the cursor moves with it, glued to its piece of