Jokes on you, because i looked into this once. I don't know the exact ms the light-sensitive rods in human eyes need to refresh the chemical anymore but it resulted in about 70 fps, so about 13 ms i guess (the color-sensitive cones are far slower). But psycho-optical effects can drive that number up to 100 fps in LCD displays. Though it looks like you can train yourself with certain computer tasks to follow movements with your eye, being far more sensible to flickering.