Amen on the TP bell curve thing. I can't stand the high end stuff, but the mid-range is great.

Generally speaking, the human brain can only really count up to 4 at a glance. Numbers beyond that slow us down.

I heard it was more like 5-6 for most people. I know for me, it's 5. The highest I've ever heard of was an Idiot Savant who could count up to 30 at a glance.