1. The induced movement has been studied experimentally in the visual field. K. Duncker (1929) wrote that the behavior of the moving objects could be explained as the displacement of the objects with respect to the frame of reference. This Phenomenon occurs also in the perceptual space of the observer, which contains his own body; it appears between the visual objects and his body. Recent experimental studies (H. Kleint (1937), P. Christian (1940) and W. Metzger (1940)), showed that the nature of this movement between the visual objects and the body was analogous to that of Duneker's.
2. The purpose of the following experiments was to see whether or not such an induced movement will occur between the parts of the body, if they are moved actually under conditions similar to those of the predecessor's experiments.
These experiments took place in a dark room. The observer sat down on a rotating chair and put his right arm on the board of a kinematometer, making a right angle with his trunk. The chair and the kinematometor were turned simultaneously or alternately to opposite directions at a certain rate in such a way that the distance between them was increased. The observer reported on the apparent movement of his trunk and of his arm, and on the directions of these movements. The speed of the movement of the chair and the kinemato-metor was changed from 5′/sec. to 20′/sec. and the distances covered were from 10° to 20°. The following three cases were examined; a) When the speed of the moving chair (here after called B) was equal to that of the moving kinematometer (here after called A), b) when A was faster than B, and c) when B was faster than A.
Results. The apparent movement of the arm was prevalent throughout all the experiments. (See Table land 3 in the Japanee text) The arm movement was especially dominant at the speed of about 10′/sec.; this was the optimal time for the induction of the movement of the visual objects (Duncker). However, the direction of the apparent movement had relation to the relative spatial positions between the arm and the trunk; the arm and the trunk sometimes moved acparently to the same direction, while they actually moved to the opposite directions (Table 2 and 4).
The direction of the apparent movement was determined by the direction of the actual movement. When B was moved actually and A was still, the direction of the apparent movement was determined by B; when A was moved and B was still, it was determined by A; When both A and B were moved, it was determined by A.
3. The relation between the actual movement of the arm and the trunk and their apparent movemet was examined by actually moving A and B to the opposite directions and by decreasing the distance between them.
Results. The simultaneous apparent movements of both A and B were prevalent (Table 5 and 7). However, their directions had no relation to the relative spatial positions of the arm and the trunk. There was also no relation between the direction of the apparent movement and that of the actual movement. The direction changed with the speed of the actual movement (Table 6 and 8).
4. E. Oppenheimer and W. krolik (1935) found that the directions of the induced movements in the visual field were not always determined by the actual movement, when the relative spatial positions of the visual objects were invariant.
The induced movement between the visual objects and the body (Kleint, Christian, and Metzger) was similar to that between the different parts of the body (present study), but the former was entirely determined by the behavior of the visual objects and the latter was not. It was determined by the directions of the actual movements. Therefore, we may distinguish between the function of the relative spatial positions of the moving parts and that of the actual movements themselvels, For this purpose we conducted the following experiments.
Both A and. B were moved
