A theory of mobility using nonvisual stimuli and cognitive control process is proposed to augment Gibson's (1958, 1979) explanations of visual guidance. Nonvisual processes are clearly important to the totally blind, who often manage considerable independent mobility in the absence of vision, but are also important to the sighted. Mobility can be directed by visual control stimuli in the ambient optic array, by nonvisual control stimuli, as well as by processes of spatial learning, including stimulus-response (S-R) rote learning, motor plans, schemas, and cognitive maps. The selection of processes and strategies depends on the availability of particular information or on task demands. Attentional processes select stimuli for locomotor control within any particular modality and select between perceptual and cognitive processes.

Measures of the accuracy of locomotion control were taken with blind and blindfolded sighted subjects using the natural auditory obstacle sense to locate a travel path. These measures were compared with the accuracy of visual guidance. While the blind show a greater skill than blindfolded sighted subjects in using auditory cues for guidance, auditory guidance is notably inferior to visual guidance and deteriorates markedly when smaller targets are used to define the travel path. The natural obstacle sense thus appears to give only a rudimentary perception of the presence of objects and does not provide sufficient spatial information to allow accurate locomotion control.

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Four blind children aged 10-30 months received training in the use of the Binaural Sensory Aid, adapted for use by children. The youngest child learned to respond to the presence of objects at 13 months. The next oldest child (21 months) learned to respond in one training session and subsequently was able to interpret distance and object-category information provided by the aid. The two older children (24 and 30 months) showed substantially less ability to respond to information provided by the aid primarily because their attention span was limited and because of competing behaviors that were incompatible with the use of the aid. Contradictions in the literature indicate the need for more reliable research methods than have been used so far. The intensive study of single cases and the use of animal research are recommended.

The relationship between sensory aid research and several areas of perceptual learning has been explored with five experiments on learning the use of the Binaural Sensory Aid, an electronic sensor in which pitch specifies distance and interaural amplitude difference (IAD) specifies direction. The training task required reaching to objects in near space, with tactile error feedback. Perceptual learning for both dimensions was demonstrated within 72 trials, giving a level of performance comparable to the use of a natural sound source, although performance with the direction cue did not reach asymptote until a second training session. Training was unaffected by various kinds of regularity in the spatial target sequences, or by a reduction in the number of spatial target locations until only two locations were used; at this point directional accuracy declines. Training only one dimension at a time did not produce additional improvement of performance on that dimension, but did impair generalization of the direction cue. Learning of the pitch-distance dimension was generally better than that of the IAD dimension, possibly because of its greater discriminability with this device. Generally, the pattern of results indicates that in learning to use such devices subjects readily determine the sensory dimensions of the codes and have considerable ability to generalize to new locations.