Illusory contours

From neurov.is/on

"Kanizsa Triangle". These spatially separate fragments give the impression of illusory contours (also known as modal completion) of a triangle

Illusory 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.

• Montaser-Kouhsari, L; Landy, MS; Heeger, DJ; Larsson, J (2007). "Orientation-selective adaptation to illusory contours in human visual cortex.". J Neurosci: 2186-95. PMID 17329415. 
• Shpaner, M; Murray, MM; Foxe, JJ (2009). "Early processing in the human lateral occipital complex is highly responsive to illusory contours but not to salient regions.". Eur J Neurosci 30: 2018-2028. PMID 19895562. 
• von der Heydt, R; Peterhans, E; Baumgartner, G (1984). "Illusory contours and cortical neuron responses". Science 224 (4654): 1260-1262.