THE PERCEPTION OF OBSTACLES BY THE BLIND
The remarkable and highly complex capacity of spatial orientation, that is, of finding one's way and maintaining a position with reference to surrounding objects, ordinarily is taken for granted by most people, including even students of psychology. The predominant and intricately organized role of visual sensitivity in spatial orientation is appreciated by few of the sighted individuals who depend upon it constantly in their everyday activities, although to scientific specialists the analysis of these visual abilities represents one of the most interesting and difficult problems in the field of space perception.1,2
When the normal-sighted individual must find his way and avoid obstacles in the dark, without a light and solely by nonvisual cues, his blundering inept movements stand in sharp contrast to the efficiency and precision of his orientation in the light and emphasize the extent to which his everyday activities depend upon visual stimuli from the surrounding environment. This contrast makes us wonder at the dexterity with which most blind individuals habitually make their way about in total darkness.
This capacity which the blind demonstrate strongly suggests the existence of environmental cues (i.e., potentially useful stimuli) other than visual ones which can adequately guide one's spatial orientation when vision is not available. It is evident that these cues, whatever they may be, are not effectively employed by most sighted individuals, who are very unskilled at avoiding objects in pitch dark or when blindfolded. On the other hand, they must be utilized by blind individuals who commonly detect and avoid obstacles readily without the aid of vision.
Such comparisons have led to much speculation about the nature of the spatial orientation of the blind, the ways in which their accom-____________________