Abstract
The Ponzo illusion refers to an apparent change in length of objectively equal parallel lines induced by enclosure within an acute angle. The present study investigated this illusory change in stimulus extent as a function of the relative depth positions of the parallel lines and the inducing angle. To permit facile and unconfounded manipulation of apparent depth, the stimuli comprising the Ponzo configuration were stereoscopic contours formed from dynamic random-element stereograms. The main results were: (1) apparent depth separation exerted a strong influence on illusion magnitude; (2) this influence was asymmetrical in that illusion magnitude decreased when the inducing angle appeared in depth behind the parallel lines and increased when the inducing angle appeared in depth in front of the lines. These data are consistent with a general theory of space perception that assumes that information about depth position is processed prior to information about stimulus characteristics.
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Fox, R., & Patterson, R.Effect of depth separation on the Ponzo illusion (Tech. Rep. N14-1101 81C-0001). Arlington, Va: Engineering Psychology Programs, Office of Naval Research, 1981.
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Support for this investigation was provided by Grants EY 00590-17, from the National Institutes of Health, and N00014-76-C-1101, from the Office of Naval Research.
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Patterson, R., Fox, R. Depth separation and the Ponzo illusion. Perception & Psychophysics 34, 25–28 (1983). https://doi.org/10.3758/BF03205892
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DOI: https://doi.org/10.3758/BF03205892