SUPPOSE YOU WERE BLIND 



enough duplication of what each can do to permit some 

 substitution of one after losing the other. 



The Sense of Obstacles 



Blindness has been an all-too-common aflSiction of 

 men, and while no device or procedure can completely 

 replace lost sight, blind men for centuries have learned 

 to get about in the world and carry on a surprising num- 

 ber of activities. Some become so skillful at avoiding ob- 

 stacles and maintaining an adequate general orientation 

 that it is difficult for a stranger to realize they are really 

 blind. For example, there was once a blind boy who 

 learned when six years old to ride his tricycle all about 

 the sidewalks near his home without injury or accident. 

 When he approached pedestrians, he steered around 

 them, and he always knew when to turn corners without 

 going into the street. Other blmd people travel widely 

 in busy cities, crossing streets, using buses and trains, 

 dodging lampposts and wire fences. How do they detect 

 these obstacles before touching them? Many theories 

 have been advanced, both by the blind people themselves 

 and by those who have worked or lived with them. Cu- 

 riously enough, the most skillful of the bUnd differ 

 widely in their explanations of their own abilities. Many 

 say they feel with then* hands or faces the proximity of 

 obstacles, and the term "facial vision" has come into 

 wide use to describe their orientation to objects which 

 are too far away to feel or touch. Others believe that 

 hearing is somehow involved; still others speak of "pres- 

 sures" and other ill-defined sensations that warn them of 

 dangers just ahead. 



The central question is obviously the nature of the 

 physical message that travels from the obstacles to the 

 bhnd man, and the way in which his remaining sense 



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