: Especially in a world without perfect motion blur, 72fps is easily
: discernable from 120fps. And depending on what you're doing (i.e. moving
: your mouse on your desktop), I'd bet 120 could be discerned from 240 and
: maybe even higher.

Perhaps it's the difference between seeing a difference in a period time versus actually distinguishing individual frames? Say you're able to distinguish 100 individual frames per second. You could still tell if something was 300fps, because it would be blurrier (each distinguished 'frame' would be composed of 3 actual frames, compared to 1 at 100fps). But you'd still only 'see' 1 distinguished frame.

I think the issue is that yes we can tell 72fps apart from 120fps or greater and whatnot, but do our brains actually see every single frame, or just a blur of frames each? (based on whatever scientifically determined frame rates)