Humans born blind or kittens raised under restricted conditions do not have the cortical regions needed to interpret visual stimuli. sensory restriction does not appear to do damage if it occurs later in life. this suggests

A critical period exists for normal perceptual development.

Explanation:

As the exercise suggests, there is a critical period for perceptual development. A critical period, as the name also suggests, is a maturational stage in the lifespan of, in this case, humans born blind and kittens, in which the nervous system is still sensitive to enviromental factors. That's why, if the sensory damage was to be done later in life, there would not be more damage. This explains the critical period for perceptual development.

the use of electrical signals that transit messages is know as

because the early people found out about it.