Although it is not yet clear 
what role such detector 
mechanisms play in visual form 
perception, the evidence 
supports the hypothesis that 
rearing animals in deprived 
visual environments will lead 
to impairment of vision. In 
fact, it would seem that the 
requirement for normal 
maturation of the visual 
nervous system (which may 
include special kinds of growth 
of neurons in the brain) rules 
out all experiments in which 
animals are deprived of normal 
vision as a source of definitive 
evidence about the innateness 
of form perception. The same 
reasoning applies to the study 
of individuals born blind who 
gain their sight; it is likely 
that these people have suffered 
some degree of impairment of 
their visual system.