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Do we see the world in 3D first?
Nick Holliman June 2023
Perception of size and length is complex, the well known Ponzo illusion demonstrates this. One explanation is that we see the world in perspective 3D and judge even 2D size and length relative to estimated 3D world distance, not simply due to the projected size on the retina [4].
Recent work [1] updates the historical view of the origins of this illusion reviewing the work of Mario Ponzo and more recent knowledge. Ponzo first discussed the illusion in 1912 [2], but referenced back to work by Sanford in 1898 [3].
You can see below how the illusion works, if you vary the size and separation of the two dashed lines in the railway scene you can vary your impression of the length of the dashed lines. The two lines are always the same size on screen.
Nick Holliman June 2023
Perception of size and length is complex, the well known Ponzo illusion demonstrates this. One explanation is that we see the world in perspective 3D and judge even 2D size and length relative to estimated 3D world distance, not simply due to the projected size on the retina [4].
Recent work [1] updates the historical view of the origins of this illusion reviewing the work of Mario Ponzo and more recent knowledge. Ponzo first discussed the illusion in 1912 [2], but referenced back to work by Sanford in 1898 [3].
You can see below how the illusion works, if you vary the size and separation of the two dashed lines in the railway scene you can vary your impression of the length of the dashed lines. The two lines are always the same size on screen.
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References
[1] M. Bertini and N. Wade, “Mario Ponzo (1928) on perception of numerosity: A translation and commentary”, Perception, Online first, May 2023, https://journals.sagepub.com/doi/10.1177/03010066231176744
[2] Ponzo, M., “Rapports entre quelques illusions visuelles de contraste angulaire et l’appréciation de
grandeur des astres à l’horizon.”, Archives Italiennes de Biologie, 58, 327–329, 1912.
[3] Sanford, E. C., “A Course in experimental psychology. Part 1: Sensation and perception.”, Heath, 1898.
[4] Dobias, J. J., Papathomas, T. V., & Sarwate, A., “Ponzo’s illusion in 3D: Perspective gradients dominate
differences in retinal size.”, Multisensory Research, 29, 421–438. https://doi.org/10.1163/https://doi.org/22134808-00002522
[1] M. Bertini and N. Wade, “Mario Ponzo (1928) on perception of numerosity: A translation and commentary”, Perception, Online first, May 2023, https://journals.sagepub.com/doi/10.1177/03010066231176744
[2] Ponzo, M., “Rapports entre quelques illusions visuelles de contraste angulaire et l’appréciation de
grandeur des astres à l’horizon.”, Archives Italiennes de Biologie, 58, 327–329, 1912.
[3] Sanford, E. C., “A Course in experimental psychology. Part 1: Sensation and perception.”, Heath, 1898.
[4] Dobias, J. J., Papathomas, T. V., & Sarwate, A., “Ponzo’s illusion in 3D: Perspective gradients dominate
differences in retinal size.”, Multisensory Research, 29, 421–438. https://doi.org/10.1163/https://doi.org/22134808-00002522