Saccadic Eye Movements

Put one finger about arms length in front of you. Now slowly sweep your finger from the far left of your visual field to the far right, while tracking your finger with your eyes. Notice how you can "see" the blurry background even if you are focused on your finger.

Now place the finger of one hand at arm's length near the border of your peripheral vision on the left and the finger of your right hand at about arm's length near the rightmost border of your peripheral vision on your right. Now quickly switch from focusing on one finger to focusing on the other finger.

By now you are probably thinking, "This is supposed to be interesting, it seems pretty routine to me." But dig a little deeper. In order for you to switch your focus from one finger to the other, your eyes "saw" everything in between. But did you experience a sweeping image, or did you see one image "jump" to the next image.

If our brain merely interprets the information from our eyes as is, you should see a fast, blurry sweep as you shift your gaze. But you don't! Somehow your brain blocks out almost all of the input from the time you decide to shift from one finger to the next. It's almost as if all that exists between one focus and the other is a timeless vacuum. The movement of focus from one object to the next is called Saccadic Eye Movement.

And where does the time go? When you looked from one eye to the other, did you perceive any delay? I don't think that I do. Although the time between looking at something on one end of your vision and the other end is only a matter of tenths of milliseconds, imagine all the times that you switch focus during a year--it must be on the order of minutes when all added together. Not to make this stray into the realm of science fiction, but where does all the time go? It seems as if your brain tells you that the time never existed.

We know so much about the human body but we know so little, and it's things like this that keep us coming back for more--despite the drudgery.