The human eye is an incredible, finely tuned, motion detecting, sexy looking piece of engineering. To function properly and be completely useful, your eyes and brain work together to calculate direction, rate of change, motion and more, all in three dimensions. Your eyes also have a function known as “smooth pursuit” which is why, when trying to slowly scan a room, you can’t help but lock onto objects. We evolved this ability to easily spot prey (or predators).
Your brain also handles the complex function of erasing the motion blur associated with moving your eyes and head quickly. It’s not a perfect process, but it works incredibly well, when sober at least.