This isn't the best test since your brain compensates for saccades by censoring input for a while. And it has built-in motion stabilization which allows you to read a sign while walking down the street.
A better test would be to look at your finger or hand while waving it very quickly. You'll see motion blur as your finger moves. In certain cases, you can see individual "frames" as an afterimage. E.g, if you look at a modern car tail light, the LED isn't on consistently but uses PWM to blink really quickly. So if you move your eyes while looking at a tail light at night, you'll see a series of dots rather than a blurry image. Once you learn this trick, you can distinguish between analog lights and PWMs by noticing if they are blurry or discrete.