Should I Still Be With The Unborn Babys Father

illusory contours



Explanation: the "white squares" which appear in the center of the two figures are created by our brain processes the boundary line of other lines that recall a figure known: the square, in fact. From
Wisebytes

another example


Again the triangle in the center (with a top-up) is not bounded by a contour line, but mentally created by the brain that is trying to "complete" the other figures (circles blacks for example).