Boundaries of objects that are not visible, but are implied by the arrangement of line segments and other visual stimuli. The effect was first reported by Friedrich Schumann (1863-1940) who influenced the the foundation of Gestalt psychology. Evidence suggests that that the perception of illusory contours emerges about 3-4 months of age, but that this ability does not manifest adult-ilke outcomes until around 7-8 months. An example of well-known figure with illusory contours is shown in the figure below.
