The present paper concerns with the way how the congenitally blinds perceive tactually the compound figures in which two or more kinds of simple geometrical contour-figures are overlapped.
In the first Experiment, the congenitally blinds were presented with sixteen overlapped contour-figuers (see Fig. 3), and asked to touch and scan freely each of them and to report what kinds of figures could be found there.
The results obtained are as follows; In general, the blinds perceive these compound figures in the different manner from that of the adults with normal sight. While the normal sees a compound figure as that consisting of two or more simple, relatively large figures (in a way, called α-type segregation for convenience), the congenitally blinds perceive tactually it as though it consists of many fragmental parts (in another way, called non-α type segregation) (see Figs. 4, 5 & 6).
In Experiment II, the adults with normal sight, closing their eyes, were presented with those compound figures and required to perceive them tactually; it was found that α-type segregation comes out almost always in their tactual perceiving of the overlapped figures. In Experiment II a, the same kind of compound figures were presented to those who had acquired blindness. Mostly those subjects attained to recognize the compound figures in the similar manner as that of the normal (see Table 2). From these results, further explorations of what psychological factors had brought about these differences in types of segregations were demanded.
In order to determine if the subject with normal sight can always attain to α-type segregation in even tactile-motor perceiving, younger children with normal sight were used as subjects in Experiment III. Various kinds of non α-type segregation was found to come out (as shown in Table 3). It therefore seems that normal sight and visual experiences are not necessarily sufficient conditions which generate the attainment of α-type segregation.
Experiments IVa and IVb were designed to examine whether or not non-α type segregation is obtained, only when a compound figure is perceived through tactilemotor system. Younger children were required to recognize stimulus-figures by peeping them through the tiny hole cut in the center of a sheet of black paper and to report what figures were hidden under the black paper. It was found that non-α type segregation would be obtained in such a situation as described, even when scanned by sight (see Fig. 10). It therefore seems not only that non-α type segregation is not specific to tactual space, but also that α-type segregation would be obtained in tactual space per se.
The final series of Experiments was planned to examine if the congenitally blind's non-α type segregation could be disorganized under the following conditions; (1) where a compound figure is presented in such a stimulus context as shown in Fig. 12 (Exp. Va), (2) where size of a compound figure is varied (Exp. Vb), (3) where new kind of a compound figure consisting of complete and uncomplete figures is presented (Exp. Vc), and (4) where one of the overlapping figures is made of noticeably different contour-line from anothers (Exp. Vd, Ve). Results of these Experiments showed that the congenitally blind's segregation, non-α type ones, was weakened, though slightly. It was discussed that further study on what determines α-type segregation would be needed.