Subjects were exposed to a three-dimensional model of a house and were asked to draw it using a raised-line drawing kit. Independent groups of ten each of sighted controls, early-blind, and late-blind subjects were told to identify the vantage point of tangible pictures of the model, including side views, 'bird's-eye' views from above, and views involving linear perspective. The ease or difficulty of picture interpretation depended upon the nature of the tangible drawing, with much better performance being recorded for side views. Performance was poor for foreshortened 3/4 views. Early-blind subjects were particularly unlikely to recognize views from above. In a control experiment with blindfolded sighted subjects the influence of prior information was examined: some subjects were told that the drawings could consist of side view or bird's-eye, top view, or 3/4 view drawings. This experiment showed that performance can be greatly improved through prior information about the nature of the tangible pictures.

The haptic horizontal-vertical illusion was studied in two experiments. In Experiment 1, the illusion was relatively weak in sighted subjects and depended on stimulus size and the nature of the figure, that is, whether the pattern was an inverted-T or L shape. Experiment 2 compared early blind and late blind subjects. The illusion was present for an inverted-T figure but absent for an L figure in late blind subjects. However, the early blind subjects treated both the Land T figures as similar and showed the illusion to both. These results support the idea that visual experience may alter haptic judgments in sighted and late blind subjects.Many researchers have been interested in discovering what tactile illusions can tell us about spatial perception (

The tactile horizontal-vertical illusion was studied as a function of hand, size, and figure (L or inverted 1'). Independent groups of subjects examined raised-line L and inverted T shapes with their left or right thumbs. The illusion varied with stimulus size and the nature of the figurethat is, with whether the pattern was an inverted T or an L shape. No illusion appeared for the L configuration. Furthermore, the strength of the illusion was linked to stimulus size, with the illusion appearing for larger inverted T patterns. The illusion vanished when the left thumb was used for haptic examination. Illusory judgments were only present for the right thumb, implicat• ing the superiority of the right hemisphere for spatial processing.