Perceptual Reversal

In some of the examples just 
discussed, I have noted that two 
(or more) organizations are 
possible. This fact brings out a 
most important point: The 
stimulus input is, logically 
speaking, ambiguous. We 
considered another instance of 
ambiguity in discussing size 
and shape constancy. An image 
of a given visual angle can 
represent objects of all possible 
sizes; only by taking account of 
distance can the perceptual 
system infer what sized object 
is producing that image.