The Pointing Instinct

Since you were six months old, you have been pointing at something you were looking at, so your pointing sequence is highly automatized due to the number of times you have pointed at a distant object. In our game, the gun must be pointed ahead of the target because the target is moving, right? 

Almost without exception, beginner shooters see the target and as they mount the gun, because of their well-honed pointing sequence, the muzzle ends up on the target and they are confused by the double image of the barrel. They don’t know which barrel image to line up with the target (even though they have been told not to look at the barrel). And they instantly consciously look at the barrel. Now there is only one barrel, but there are two targets! 

This is called physiological diplopia. In the beginning, it can be very confusing, especially if the shooter is looking down the barrel. When each axis of the eyes focuses on something, the axis comes together at the same point and the brain sees the object in detail. But while focused on the object, anything in front or behind the object will be seen as a double image, which can be quite confusing.