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

The Mind's Eye | 275object doesn't match a view spot-on, one can get away with storing amanageable number of views per object, forty at most.It still seems unlikely that people have to see an object from forty differentangles to recognize it thereafter, but another trick is available.Remember that people rely on the up-down direction to construeshapes: squares aren't diamonds, sideways Africa goes unrecognized.This introduces another contamination of the pure geon theory: relationslike "above" and "top" must come from the retina (with some adjustmentfrom gravity), not from the object. That concession may be inevitable,because there's often no way of pinpointing the "top" of an object beforeyou've recognized it. But the real problem comes from what people dowith sideways objects they don't recognize at first. If you tell people thata shape has been turned sideways, they recognize it quickly, as you surelydid when I told you that the Africa drawing was on its side. People canmentally rotate a shape to the upright and then recognize the rotatedimage. With a mental image-rotator available, the object-centered frameof the geon theory becomes even less necessary. People could store some272-D views from a few standard vantage points, like police mug shots,and if an object in front of them didn't match one of the shots, theywould mentally rotate it until it did. Some combination of multiple viewsand a mental rotator would make geon models in object-centered referenceframes unnecessary.With all these options for shape recognition, how can we tell what themind actually does? The only way is to study real human beings recognizingshapes in the laboratory. One famous set of experiments pointed tomental rotation as a key. The psychologists Lynn Cooper and RogerShepard showed people letters of the alphabet at different orientations—upright,tilted 45 degrees, sideways, tilted 135 degrees, andupside down. Cooper and Shepard didn't have people blurt out the letter'sname because they were worried about shortcuts: a distinctivesquiggle like a loop or a tail might be detectable in any orientation andgive away the answer. So they forced their subjects to analyze the fullgeometry of each letter by showing either the letter or its mirror image,and having the subjects press one button if the letter was normal and theother if it was mirror-reversed.