Shrinkage and expansion by amodal completion: a critical review

The whole literature on the so-called dimensional effects of amodal completion (shrinkage of a partially occluded figure and expansion of modally visible parts of the same figure) is critically reviewed. It is claimed that phenomenal shrinkage is the sum of at least two illusions independent of figure ground distinction: (1) shrinkage of spaces divided into a few parts, and (2) shrinkage of empty spaces. It is also shown that a partially occluded figure can widen, rather than shrink. It is concluded that the stratification in two phenomenally superimposed figures accompanies the shrinkage effect, but is irrelevant to its generation. Further experiments are needed in order to draw a well-grounded conclusion on the expansion effect.