Depth adjacency and the rod-and-frame illusion

Abstract

In Experiment I, the tactile adjustment of a comparison bar was used to measure the change in the rod-and-frame illusion as a function of the stereoscopic position of the rod relative to the frame. A vertical rod was presented at a near, a middle, or a far distance, with a single frame tilted counterclockwise at the near distance, a single frame tilted clockwise at the far distance, or two frames of opposite tilt presented simultaneously at the near and far distances. When only one frame was present, displacement of the rod in front of the far frame but not behind the near frame significantly reduced the illusion. When both frames were present, the illusion was determined mainly by the frame at the apparent distance of the rod. In Experiment II, the tactile method of measuring perceived tilt was validated for the range of perceived tilts encountered in Experiment I. The results of Experiment I are discussed in terms of the perceptual resolution of the conflict between relative and absolute cues of tilt. © 1975 Psychonomic Society, Inc.