Illusory contours
Illusory contours or subjective contours are a form of visual illusion where contours are perceived without a luminance or color change across the contour. Friedrich Schumann discovered illusory contours.[1]
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[edit] Examples
A classic example of illusory contours is the Kanizsa triangle[2], named after the psychologist Gaetano Kanizsa. This figure comprises three black circles with equal wedges cut out of them facing the center point and three black angles on a white background. But many observers see a white triangle on top of three black disks and an outline triangle. The white triangle appears brighter than the white background and shows a contour even in regions where there is no luminance change in the image.
The Ehrenstein illusion is another example form of illusory contour.
[edit] Explanation
It is thought that early visual cortical regions such as V2 are responsible for forming illusory contours.[3]
[edit] See also
[edit] Notes
- ^ Schumann, F (1900), "Beiträge zur Analyse der Gesichtswahrnehmungen. Erste Abhandlung. Einige Beobachtungen über die Zusammenfassung von Gesichtseindrücken zu Einheiten.", Zeitschrift für Psychologie und Physiologie der Sinnesorgane 23: 1–32
- ^ Kanizsa, G (1955), "Margini quasi-percettivi in campi con stimolazione omogenea.", Rivista di Psicologia 49 (1): 7–30
- ^ von der Heydt, R; Peterhans, E; Baumgartner, G (1984), "Illusory contours and cortical neuron responses", Science 244 (4654): 1260–1262, doi:10.1126/science.6539501, PMID 6539501
[edit] References
- Coren, S (1972), "Subjective contour and apparent depth", Psychological Review 79 (4): 359–367, doi:10.1037/h0032940, PMID 5038153
[edit] External links
- Illusory contours figures Many unpublished drawings (fr)
