A. Stereogram in which retinal 
disparity and interposition 
both indicate that the vertical 
bar is in front of the horizontal 
bar (solution C.) B. Stereogram 
in which disparity indicates 
that the vertical bar is in front 
whereas interposition 
indicates that the horizontal 
bar is in front. Interposition 
usually dominates, but other 
perceptual solutions are 
possible, such as seeing two 
unconnected vertical segments 
floating in front of the 
horizontal bar (D) or seeing the 
horizontal bar curved around 
in depth (E.)

In stereogram A shown at left, 
retinal disparity leads to the 
perception of a vertical bar in 
front of a horizontal bar, as 
does the interposition pattern. 
But suppose instead the overlap 
pattern leads to the impression 
that the horizontal bar is 
closer, even though disparity 
alone would lead to the opposite 
effect. In such situations, 
interposition, a mere pictorial 
cue, usually dominates 
stereopsis, considered by many 
to be the physiological cue par 
excellence, probably innately 
determined and present in 
many animal species. (Of course 
there are individual 
differences in the way such 
cue-conflict experiments are 
resolved, so that some 
observers may see an 
incomplete, broken vertical bar 
in front in the figure.)