Classical and inverted White's effects

In classical White's effect, intermediate-luminance targets appear lighter when they interrupt the dark stripes of a grating and darker when they inte rrupt the light stripes. The effect is reversed when targets are of double- increment or double-decrement luminance, relative to the luminances of grat ing stripes. To find a common explanation for classical and inverted effect s, we ran two experiments. In experiment 1, we utilised intermediate-target displays to show that perceived transparency dominates over occlusion only when the target luminance is close to the luminances of top regions. This result weakens transparency-based accounts of White's effect. In experiment 2, we varied grating contrast and target luminance to measure the classica l effect in seven intermediate-target cases, as well as the inverted effect in four double-increment and four double-decrement cases, Both types of ef fect are explained by a common model, based on assimilation to the top regi on and contrast with the interrupted region, weighted by adjacency along th e luminance continuum.