The belongingness theory has been given as an explanation of White's illusion. Belongingness means that we perceive things depending on its surroundings. According to belongingness theory, the lightness of rectangle A is influenced by the white bars that surround it. Similarly, the rectangle B on the right side is surrounded by the dark bars. So, the lightness of rectangle B is affected by the dark background. As a result, area A which rests on the white background appears darker than area B which rests on the dark background.