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Fig. 13.3. Edge-induced vs. line-end-induced illusory contours. The figures illustrate the two mechanisms believed to underlie the process of forming illusory contours in the visual system: (a) The hovering white triangle is formed by edge inducers, i.e. by continuing the separate, collinearly aligned edges, and (b) the bright circle in the middle is composed by line-end inducers, i.e. by connecting the ends of the lines into a continuous circle.