Before this figure is perceived 
as a transparent square in front 
of a background of differing 
lightnesses, it may be 
fleetingly perceived as eight 
regions of different lightnesses 
in the same plane.

    The resulting perceptions 
that occur at this stage are 
highly correlated with the 
organized stimulus thought of 
as a two-dimensional array. For 
example, the transparency 
pattern that appears here looks 
like several separate regions of 
differing lightnesses, and a 
distant object may look small, 
or a circular one like an 
ellipse. However, these 
proximal or literal mode 
percepts are fleeting, and often 
we are unaware of them.

    Such fleeting percepts are 
immediately superseded by 
perceptions that more 
veridically represent the world 
and that therefore might be 
referred to as perceptions in 
the world (or constancy) mode. 
Again, attention must be a 
prerequisite for the 
achievement of this level of 
perception. The literal or 
proximal mode percepts 
remain, although they inhabit 
the background of our 
awareness and are not so easily 
brought to the center of 
attention. The world-mode 
perceptions are based upon, 
among other things, further 
processes of organization. For 
example, in the case of an 
interposition pattern, figure-
ground organization within the 
pattern leads to the impression 
of one unit overlapping 
another. Or, to give another 
example, the pattern in the 
illustration at left, which at 
first may have looked like eight 
regions of differing 
lightnesses, tends to look like a 
small, transparent square 
through which one is looking 
at another larger, black-and-
gray pattern. The latter 
(transparency) percept is 
preferred, much as is the 
overlapping percept in the 
previous example. These 
perceptions refer to structures 
arranged in three-dimensional 
space. Moreover, as we saw in 
Chapter 5, if more than one 
object is encountered, it is the 
one to which we attend that 
will undergo the description 
processing that leads to the 
perception of a distinct shape.