There can be alot of confusion over the different types of aiming techiniques because some meld into one another as an archer learns his particular techinique.
True Total Instinctive Aiming - is where the archer isn't CONSCIOUSLY using the arrow, gap or any other object besides the target within their vision as a reference while aiming. The aiming is primarily done within the subconscious using proprioception and muscle memory. It's very similar to how a well trained athlete performs a specific movement to achieve a specific goal without having to analize it or think about it.
If an archer is CONSCIOUSLY using the arrow to line up the target...they are not aiming TOTALLY instinctively...even if they are not analizing the gap.
If an archer is CONSCIOUSLY aware of the gap between some reference and the target and is CONSCIOUSLY making adjustments to the gap in relationship to the target...they are not aiming TOTALLY instinctively.
My primary aiming techinique is basically Gap aiming. I've been aiming Gap for so long that many of it's techiniques have almost become totally instinctive. I no longer consciously analize what my exact gap needs to be for a certain distance. I feel it...yet I am CONSCIOUSLY aware of my arrow in relationship to my target. I CONSCIOUSLY recognize the correct sight picture for a specific target and distance but I couldn't tell you exactly what it is. I know it when I see it. I can tell you what it probably looks like...but a True Instinct Aimer couldn't tell you at all.
Many archers, who use 3 fingers under, use it to decrease the gap between the target and the arrow tip and use the arrow as if they were looking down a gun barrel.
When an archer consciously uses the arrow to line up the target and/or create a specific gap between the target and the arrow tip, they are basically Gap aiming even when they aren't analizing exactly what the gap needs to be or exactly how far the target is.
There can be a fine line between Gap aiming and Instinctive Aiming especially when an archer has mastered their Gap aiming techinique.
Ray