Global belongingness factors can give rise to White's effect.

Munker-White's illusion is an optical effect illustrating the fact that the same target luminance can elicit different perceptions of lightness in different contexts. White's effect is consistent with simultaneous contrast. Agostini and Proffitt (1993 Perception 22 263-272) showed that perceptual belongingness (the subsumption of some set of elements into a perceived whole) could cause simultaneous lightness contrast to be seen in configurations in which the inducing elements are not adjacent to the target. In the present work, in Agostini and Proffitt-type config- urations we obtained, by means of the perceptual organisation factors of similarity and good continuation, displays in which a White effect determined by belongingness in absence of spatial contiguity is achieved. The factors we manipulated were achromatic colour (high-low reflec- tance) and shape (circle-square) of the inducing elements of the display, which was always placed on a mid-reflectance background. We tested also double-increments and double-decrements conditions. Even if there are no junctions at all, the classic White effect can be observed. Results are discussed within the relevant literature.