[Aisthesis]

I think the math is absolutely impossible to do on the spot in some situations. I think it comes with lots of experience (having run various hands through 2dimes) that you just kind of "know" what shape you're likely to be in.

Just counting outs on the spot isn't completely trivial, then if you try to get into stuff like "well, I think he has AA with flush draw 40% of the time, a wrap 30% and top set 30%, so can I really call/raise with middle set?" all I know is that it's probably near marginal without doing a REALLY elaborate calculation.