In figure 5 of this paper (page 1037) the upper right display was printed too dark, so that the squares surrounding the grey diamond became black, merging with the grid.
A lighter version of this figure is shown below.
Figure 5. Top display: the dungeon illusion, in its ‘same-ratio’ version. The small grey squares that form the two diamonds are all the same shade of grey, and are all completely surrounded by black areas, but the diamond that appears to lie on the white background (left) looks darker. Bottom display: the dungeon illusion, in its ‘wrong-ratio’ version. The small grey squares that form the two diamonds are all the same shade of grey, but the diamond whose elements are completely surrounded by black areas (left) looks darker. The effects are stronger when the displays are viewed from a distance.
