That’s a silly experiment. I could look at a CRT with a completely static image and tell almost immediately whether it was at 60Hz, 90Hz or 120Hz. Flickr at 60Hz was awful, 90Hz was clearly perceptible, and even 120Hz was often somewhat noticeable. And most CRT/graphics card combos would become perceptibly blurry in the horizontal direction at 120Hz at any reasonable desktop resolution, so you could never truly win. Interlaced modes made the flicker much less visible, but the crawling effect was easy to see and distracting.