Visual After-Effects in the Third Dimension: the Importance of Margins

Visual after-effects in the third dimension were studied under four different conditions. In each case subjects viewed a surface slanted from the frontal plane at 67 degrees. In the first condition this surface had a regular, horizontal texture and was seen through a square window that hid its edges. In the second condition the same surface was seen between margins which, of course, appeared to converge with distance due to perspective effects. In the third condition the texture was oriented vertically, and seen through the window. In the last condition the surface from the third condition was seen with margins as in the second condition. After having inspected this surface for 5 sec, subjects had to judge the distances of two vertical, parallel lines, shown for 250 msec. The results show that the line falling in the place that corresponded to the more distant part of the surface was seen as nearer than the other. This illusory displacement was stronger when the texture of the surface was vertical, and wh...