Effect of Depth Separation on the Ponzo Illusion.
Abstract
The apparent lengths of objectively equal line segments are altered when the segments are enclosed within the arms of an acute triangle. This distortion, which occurs in many natural environments whenever linear perspective cues predominate (e.g., an aircraft runway), is known in the laboratory as the Ponzo illusion. This experiment tested the hypothesis that the illusionary change in length would depend upon the relative depth positions of the triangle and the line segments. That hypothesis arose from prior research which indicated that the destructive interaction among spatially adjacent contours present in such phenomena as visual masking and lateral interference depended strongly on the relative depth positions of the interacting contours. The Ponzo illusion provided a stimulus configuration for determining if the effect of depth position applied to interactions that are not destructive. To provide facile manipulation of depth position the Ponzo stimuli were generated as stereoscopic contours formed from dynamic random-element stereograms. This approach permitted depth position and other parameters to be readily manipulated without introducing potentially confounding changes in proximal stimulation and in the apparent size of the stimulus elements. Estimates of illusion magnitude were obtained under a series of depth positions in which the test lines appeared in depth in the same plane as the triangle and either in front of, or behind the plane of the triangle.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1981
- Accession Number
- ADA098925
Entities
People
- Robert E. Patterson
- Robert Fox
Organizations
- Vanderbilt University