Size Constancy: The Taking-
into-Account Explanation
Objects of the same size seen at 
different distances: size 
constancy is achieved if the 
distances are correctly taken 
into account.

Because of the weaknesses in 
the stimulus-relation 
explanation of size constancy, 
some investigators have 
rejected it in favor of an 
inference explanation, in 
which distance is taken into 
account in size perception. 
According to this theory, the 
perceptual system--the system 
in the brain that is concerned 
with perception--engages in an 
operation of computation that 
includes both an object’s visual 
angle and its perceived 
distance. (The actual cues we 
use to determine an object’s 
distance will be discussed in 
Chapter 3.)