Gaetano Kanizsa1913–1993
Illusory contours, 1955
Italian psychologist whose triangle of notched discs showed the eye drawing edges that are not there.
Kanizsa Contours
Discs with a bite taken out of each. The shape between them has edges, a surface and a brightness, and none of it is drawn.
About this pattern
Gaetano Kanizsa, 1955
Kanizsa's figure: cut a wedge from each of several discs, aim the wedges at one another, and a polygon appears over the top of them, brighter than the page it sits on, with edges that cross blank paper. The visual system prefers one whole shape occluding intact discs to several coincidentally bitten ones.
Turn the wedges away with the alignment control and the shape does not fade, it stops existing.
Behind the mathematics