Is the "bead" a necessary aiming device or a distraction?
Shotgunning is a point and shoot activity. Successful shotgun shooting is directly related to good hand-eye coordination. Assuming your gun fits you reasonably well, the prelude to the shot goes something like this: Focus on target, Move, Mount, then Shoot.
Nowhere in that sequence will you see "Look at the bead" or "Line up the bead."
The bead or sight on a shotgun is a point of reference. The real usefulness of a bead only pertains to stationery targets. The bead serves as a sight to point the gun at a target.
The bead is also a reference to determine if your gun mount is consistent. If you are mounting the gun dry or shooting at a patterning board, the bead is a constant that can reveal inconsistencies.
For example: If you mount the gun and do not see the bead at all, your cheek is most likely too low. It can also indicate that the comb of the gun is too low to fit you properly.
Conversely, if you see the whole barrel and are looking down at the bead you either a) are lifting your head up off the stock, or b) the comb is too high for you.
Some shotguns have the "Mysterious Middle Bead." While it is generally referred to as the middle bead, it is actually the rear bead; it is not the middle of three beads. It gets the name "middle" because it is usually halfway down the barrel.
Many people don't know the purpose of a middle bead on a shotgun or how to use it. The middle bead works in conjunction with the front bead so you have two points of reference. It is similar to marking a board at two points so you can cut a straight line between them.
The two bead system works by creating a small figure eight out of the two beads. The front bead is the top portion of the figure eight and is often slightly larger than the middle bead.
The idea is that when the two beads form a perfect figure eight, your eye is lined up exactly down the center of the barrel. There is another type of bead that accomplishes the same thing with one front bead. This concept was originally manufactured in the 1960s as the Accu-Sight but disappeared from the market for decades. A very similar design was recently reintroduced as the Uni-Dot.
The bead is actually a small fiber optic rod captured in a small metal tube. It is installed so the rod is perfectly centered on the barrel. When you mount the gun you will not see the colored dot unless your eye is perfectly centered over the barrel.
Using the bead or beads for gun mounting reference or for shooting stationery targets (like turkey) helps the shooter adjust head position so the gun shoots where the eyes are looking. In shooting flying targets, sight fixation is one of the worst things a shooter can do.
When a gun fits you properly, it is an extension of your body. When properly mounted it will shoot exactly where you are looking. There is actually no need for any bead at all on a bird gun.
Human eyes cannot focus at two distances at once. If you look at your bead, the target is not in focus. When you try to line up two beads, focus on one bead or look for the colored dot. With a fiber optic sight your physiological response is to stop or slow down the gun, causing a miss.
Concentrate on the target - focus, focus, focus. Let the gun be an extension of your body and you will hit what you are looking at.
In other words, don't look at the bead.