Nevertheless, size 
proportionality is probably not 
the major explanation of either 
size perception or size 
constancy. In the examples just 
cited, for instance, the 
dramatic effects are primarily 
the consequence of our 
interpretation of the picture 
and our interpretive 
acceptance of an altered scale 
rather than the consequence of 
our actual perceptions of size. 
In examples more typical of 
daily life, our perceptions of 
size change only slightly with 
varying contexts. Furthermore, 
the results of the 
proportionality experiment, 
impressive as they are, are not 
good enough to explain 
constancy. Further 
experiments have established 
that, if the difference in the 
size of the rectangles is greater 
than the 3:1 value described 
above, the result departs even 
more from the proportionality 
prediction. Yet when one 
compares a scene such as a 
person next to a house viewed 
from 1000 meters with that 
scene viewed from, let us say, 
10 meters, the difference 
between visual angles of the 
house is equivalent to an 
experiment with frames of 
reference that differ by 100:1. 
While full constancy might 
well occur in such a real-life 
comparison, the result of an 
experiment on line matching 
with two rectangles that differ 
by 100:1 would depart 
appreciably from a 
proportionality prediction. As 
for Gibson’s theory, it 
maintains that constancy does 
not simply depend upon the 
occlusion by objects of an equal 
number of units in the texture 
of the plane. It also requires 
that the plane is perceived to be 
receding in depth with textured 
units that are perceived as 
equal and everywhere 
equidistant from one another. 
Naturally, if that is true, 
objects at different distances 
that cover an equal number of 
texture units are, almost by 
definition, equal in size. If, 
however, the textured surface 
does not look like a receding 
plane, the effect does not 
occur.