pictures are familiar, inspection of pictures of a well-known kind of object will be a swifter process. Blind children tested in Arizona ( Kennedy, 1982b, in preparation) were proficient at tactile exploration, and identified tactile pictures at a rate exceeding blind children in Haiti, occasionally recognizing more than 50% of a sample of pictures. The Haitians could draw more effectively, possibly because manual skill in crafts and woodworking were stressed in their school.
We anticipate that tactile exploration of pictures, as it becomes more proficient, will allow larger chunks of the display to function as units, and to be grasped quickly. The role of junctions will become more evident. Ambiguities will be dispelled more rapidly. Alternatives will be sought more effectively and more quickly. Less time will be spent stuck on first impressions. In this connection, ultrasound pictures may be a helpful analogy. Initially these are incomprehensible to the sighted. To the expert, they reveal a great deal about the womb and the fetus within. Compare the line drawings replicating chiaroscuro structure in Fig. 11.7, which are mere ciphers as far as vision is concerned. No amount of experience, we predict, with outline versions of chiaroscuro structure will enable such displays to show vivid and comprehensible referents to human vision. They will never produce apparent shadow akin to the apparent depth in outlined relief. Outline depiction occurs, we contend, in perceptual pathways that are actuated after chiaroscuro has been analyzed and axes of lines registered. Like visual pictures, haptic pictures, the evidence indicates, are surrogates for relief. The question that demands a response is how extensive and comprehensive a pictorial facility can be built in touch on this foundation. In one sentence our response is: Form principles of depth and slant used by vision are also used by touch, and can stand on the foundation that lines depict relief corners and occlusions.
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