Try this (and I really do mean it… do this):
Tie a washer onto a string that is about 12 inches long.
Take a blank piece of letter-sized paper and draw a large plus sign (+) in the center of the page so that it takes up most of the page.
Hold the end of the string between your thumb and forefinger, rest your elbow on the table, and dangle the washer directly above the middle of the +.
While keeping your hand still, focus your vision on one end of the perpendicular line that make up part of the +.
Now switch your visual focus — not quickly, but relatively slowly — to the opposite end of that line; then switch your focus back to the end that you started on; then to the opposite end again; continue to move your focus from one end of the line to the other and back again.
Be sure to really focus intensely on the ends of the line before switching back to the opposite end, up and down, but keep your visual focus moving smoothly.
Do this for at least 30 seconds.
Did you notice that the washer began to swing, if even just a tiny bit, as if it was following your vision from one end of the line to the other?
Now, switch your focus to the horizontal line making up the +, and alternate from end to end of it. Visually follow this line back and forth for at least 30 seconds.
What happened? Did the washer switch from following the first line to the other line at a 90-degree angle to the first line?
That’s the power of visual focus.