How to read what a hitter is sitting on?

I’d like to know more about how as a pitcher we can deduce what a hitter is sitting on, from how he reacts to different pitches.

For example, I throw him a 0-0 fastball right down the middle, and he takes it without blinking. Does it mean he was sitting on something soft? What if it’s 1-1 or 2-1 count? What can we deduce from a hitter taking a fast-ball for a strike?

Similarly, what does it mean if a hitter takes a breaking ball for a ball without flinching on 1-1 or 0-1 count? He was sitting on soft, and was able to lay it off?

Same question, but when he takes a breaking ball for a called strike?

In general, I’d like to know what are ways to deduce if a hitter is sitting hard or soft. Thank you!