Face or vase? Areal homogeneity effect.

To examine the effect of homogeneity of area in figure-ground organization, we made several variations of Rubin's goblet. Observers were required to judge whether they perceived a goblet or profiles (faces). Our results showed that, when both profiles were the same lightness, the percentage of judgments (goblet vs profiles) were almost equal. When the profiles were different in lightness, so that the homogeneity of the profile areas was broken, observers were more likely to perceive the profiles. When both profile areas had horizontal stripes or concentric circles and the homogeneity of the profile areas was strengthened, those areas tended to be perceived as ground. We concluded that (1) a difference in lightness was sufficient to break up the homogeneity of the profile areas; (2) good continuity was an eminent condition for unifying profile areas as ground.