1) When you visit the optometrist and you are asked to concentrate on and read the smallest line of letters you can. What happens to all the other lines of letters, they disappear.
2) If you place thee objects on a table about 4 or 5 yards from you and about 3 feet between each one. For example, three containers with labels on them, with the labels facing away from you. You initially observe the three containers. However, if you turn the centre container. Then concentrate on reading the small print on the label. You will find the left and right containers are no Longer in your vision. They have disappeared and are no longer influencing your visual or mental input.
If you concentrate on a specific minimum target on the golf course you get the same result. All obstacles and hazards that normally have a negative effect on your shot have disappeared. In other words the course has disappeared leaving you to play a stress free shot to the selected target. No negative mental input or self doubt. When you practice your
putting remember the smaller your target the smaller the miss. A good focus can be practiced with a tee stuck in the back of the cup, putt to the tee not the hole. This finite focus lends to precision.