Does frequency of eye blinking reveal anything about human biology/nervous system?
People avoid looking at what they don't like thinking about.
A feared enemy, an individual whom you have something to hide from..

Avoidance of looking/excessive blinking is a sign of fear.
It's basically a sign that the individual is not having a good time looking at what he is looking.

Sometimes people are lying and then they don't like looking at whom they are lying to... for them it would be nicer to look out the window or something that takes them away from their subject for a bit of time.
I would expect blinking to increase when lying.

Personally I have noticed excessive durational closing of eyes (a second or so), exactly at the moment of stating their lie.
Those are off course people who are honest to themselves but are trying to be dishonest to you. But some people lie to themselves as well and they may be more difficult to detect.