For animals, including 
humans, successful navigation 
through the world and survival 
itself depend upon accurate 
distance perception. For 
centuries, philosophers and 
natural scientists were split 
into two camps with respect to 
the question of the origins of 
the perception of the third 
dimension. The Nativists 
maintained that space 
perception was an innate 
faculty of the mind (or, in more 
modern terminology, that the 
perceptual system was 
programmed or prewired for 
three-dimensional perception). 
The Empiricists maintained 
that such perception in the 
adult was the end result of past 
experience in infancy and 
early childhood. The 
controversy was carried on 
mainly with logical arguments. 
Only in recent years have 
experimental techniques begun 
to resolve the issue, as we shall 
see.

    For both sides of the 
question, the problem remains: 
What information is available 
to the perceptual system that 
enables us to achieve adequate 
impressions of distance and 
depth?