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

The Mind's Eye | 227beyond it. (Some people place a pane of glass or a transparency on top ofthe stereogram, so they can focus on the reflections of distant objects.)You should still be seeing double. The trick is to let one of the doubleimages drift on top of the other, and then to keep them there as if theywere magnets. Try to keep the images aligned. The superimposed shapesshould gradually come into focus and pop in or out to different depths.As Tyler has noted, stereo vision is like love: if you're not sure, you're notexperiencing it.Some people have better luck holding a finger a few centimeters infront of the stereogram, focusing on the finger, and then removing itwhile keeping the eyes converged to that depth. With this technique, thefalse fusion comes from the eyes crossing so that the left eye sights aboat on the right while the right eye sights a boat on the left. Don't worryabout what your mother said; your eyes will not freeze into that positionforever. Whether you can fuse stereograms with your eyes crossed toomuch or not enough probably depends on whether you are slightly crosseyedor wall-eyed to begin with.With practice, most people can fuse wallpaper autostereograms. Theydo not need the yogi-like concentration of the psychologists who freefusethe two-picture stereograms, because they do not have to uncoupletheir focusing reflex from their convergence reflex to the same degree.Free-fusing a two-picture stereogram requires jamming your eyes farenough apart that each eye remains aimed at one of the pictures. Fusinga wallpaper stereogram requires merely keeping the eyes far enoughapart that each eye remains aimed at neighboring clones inside a singlepicture. The clones are close enough together that the convergence angleis not too far out of line from what the focusing reflex wants it to be. Itshouldn't be too hard for you to exploit this small wiggle in the meshbetween the two reflexes and focus a wee bit closer than your eyes converge.If it is, Ellen DeGeneres may be able to get you into her supportgroup.The trick behind the wallpaper stereogram—identical drawings luringthe eyes into mismatching their views—uncovers a fundamental problemthe brain has to solve to see in stereo. Before it can measure thepositions of a spot on the two retinas, the brain has to be sure that the