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

The Mind's Eye 279Now, Cooper and Shepard's subjects may have been doing the samething, except that they were rotating the shape in their minds instead ofin the world. To decide whether they were seeing a normal or a backwardsR, they mentally rotated an image of the shape until it wasupright, and then judged whether the imaginary loop was on their rightside or their left side.So Cooper and Shepard have demonstrated that the mind can rotateobjects, and they have demonstrated that one aspect of an object's intrinsicshape—its handedness—is not stored in a 3-D geon model. But forall its fascination, handedness is such a peculiar feature of the universethat we cannot conclude much about shape recognition in general fromthe experiments on mental rotation. For all we know, the mind couldoverlay objects with a 3-D reference frame (for geon matching), specifiedup to, but not including, which way to put the arrow on the side-tosideaxis. As they say, more research is needed.The psychologist Michael Tarr and I did some more research. We createdour own little world of shapes and despotically controlled people'sexposure to them, aiming at clean tests of the three hypotheses on thetable.J .The shapes were similar enough that people could not use shortcutslike a telltale squiggle. None was a mirror image of any other, so wewould not get sidetracked by the peculiarities of the world in the lookingglass. Each shape had a giveaway little foot, so people would neverhave a problem finding the top and the bottom. We gave each personthree shapes to learn, and then asked them to identify the shapes bypressing one of three buttons whenever a shape flashed on a computerscreen. Each shape appeared at a few orientations over and over. Forexample, Shape 3 might appear with its top at four o'clock hundreds oftimes, and with its top at seven o'clock hundreds of times. (All theshapes and tilts were mixed up in a random order.) People thus had theopportunity to learn what each shape looked like in a few views.