I'm not saying the human eye can't detect higher and higher amounts of frames, i'm saying if you don't know the framerate of what you're looking at, no fps counter, and all you see is smooth motion, how do you tell if its 40 fps, 60, or 100 fps? Do you actually get a sense of it being more and more smooth or is it just one flat "smooth" motion across the board? Thats my point.
And sorry for derailing the topic.