Psychological 
Aspects 
    
Important Psychological Aspects — subjective and variable properties. 
Red is said to be an emotional colour - this statement leads right into 
the psychological domain of vision. 
The NEURAL CHAIN to the BRAIN still has anatomical 
aspects. In fact, if the retina is considered as a 
  
  
  
  
part of the brain, then there is not much chain 
left, unless the central part of the brain - the 
cortex — is meant. The anatomy is apparent in the 
basic connections: at the central part of the fovea 
each cone has its own nerve connection, towards the 
edge of the retina, many rods join a single nerve S 
chaine V 6 
Electrical signals pass through the chain; frequency modulated to 
prevent loss of signal. Nevertheless there are deteriorations, such as 
"after effects" (temporal inhibition), and spatial inhibition (seeing 
black dots on the crossings of the white bars between a mosaic of large 
black squares). 
À typical property has relevance to photo-interpretation: the connec- 
tions of the right eye with the left cortex and of the left eye with the 
right-hand brain section cross each other and partly join, in order to 
permit correlation of the two signals. 
With stereo viewing, most operators are not aware which eye sees 
what — but some seem to have (or have developed) an "absolute" stereo 
feeling; they cannot be fooled by pseudo image pairs and unusual shadows 
o 
or other false clues. (Goosen, 1967, private comm. ). 
[The neural chain is developed and maintained by training - it even © 
seems that this goes on for a lifetime — and the various parts of the b € 
network may join and cooperate or influence each other in innumerous 
ways, as if a very capable telephone operator makes the optimum 
connections for each task anew. 
For instance, the time and exercise needed to set up a completely 
new scheme when wearing upside-down prism as permanent spectacles, 
is at least three days. This is also the time photogrammetrists and 
photointerpretors need in order to adapt to a completely different 
type of imagery. It is of no use to try to evaluate radar images 
haphazerdly, if your occupied time does not allow 3 complete days 
for & limited brain-wash; better put & younger cooperator on such 
a task.]