Narced or not has nothing to do with what you feel. The Nitrogen Narcosis is a physical law which there is no way to escape any more than the effect alcohol has on your system. Divers claiming that they are not narced is also the same kind of people who would say "I only had two beer. I can drive".
The whole point with the deep dive training is to help divers understand just that: You are narced even if you don't feel it. During AOW courses I teach I always tell my student that the Deep Dive is not about determine if you are narced. It's about getting you to realise that you are. Knowing the signs and symtoms of nitrogen narcosis is important so you know that you are narced and can deal with that in a stressful situation...
I agree with you that narcois is something that happens to everyone and that deep diving training is designed to help divers recognize it. If you go to 150' on air and try to do anything significant, you will recognize the narcoisis (if you do not, deep diving is something you probably need to avoid) and more importantly you will recognize being narced to a far lesser degree at much shallower depths - even 60 ft.
It is interesting watching a cave diver with limited deep diving experience put in and remove a jump reel at 30' with reasonable speed and ease and then watching them struggle trying to do the same thing at 100'. Simple things like remembering which way did I wrap it around the mainline or which way do I want to go now that I placed it can be much harder problems at a bit more depth than you usually perform the task or solve the problem.
The reasons a diver with significantly more expereince, and more importantly more experience at depth will do it more efficently do not relate to a lessened degree of narcosis but rather a much higher degree of accomodation. For example the experienced diver may have put in reels hundreds of times and very likely has a very set way of doing it that they have in essence over learned (along with perfect buoyancy, and all the other basic skills that then help them reduce task loading at depth as they do not have to devote attention to them). In my case, I always start by placing the jump line over the top of the main line and wrapping under it. I then know that when I remove it that I need to lift the ball on the end of the line straight and push the reel back through the loop that forms under it instead of wondering which way is which. I
need to do it that way as I recognize if I do not do it the same time
every time I will not remember how I did this particular time at 100'. In addition, at 44, seeing which way a tiny piece of line wraps under or over anothertiny piece of line the smae color is not as easy as it was 10 years ago, so consitency also accomodates reduced near vision acuity in low light (and in really silty conditions.) I also previsualize what I need to do and break it down into simple terms and steps so that when ever possible, the major problem solving does not have to occur at depth.
But frankly people also vary. I think everyone's situaional awareness shrinks as the END gets deeper as does everyone's ability to problem solve and their overall cognitive resources diminish. Accommodation and over learning of tasks greatly helps as it lowers the burden placed on the limited higher level intellectual resources. However to be blunt, some divers start out with a lot less in the intellectual checking account than others. Consequently, the level where you start writing intellectual bad checks varies based on experience, prior learning and the demands of the dive, but also from diver to diver.
...It's easy to test though. Next time you're on 45 metres with him ask him how much air he's got and then ask him to divide this amount in half.
Messing with comunication about air status is a really bad idea. If I ask my buddy how much gas he has left I do not want to encounter the possible situation where a request for the information is confused with a test. There is too much potential that he will skip the initial request and go straight to the test - especially if he is narced.
It works just as well to show your buddy a certain number of fingers and ask him to show you two less fingers in return. If you arrange to repeat the test twice, each time you do it, you can use one hand the first time (say 4 fingers that he correctly returns with 2 fingers) then use both hands the second time (7 fingers), but bring the other hand up slowly and 3 ft away. If he is perceptually narrowed, he will quite possibly respond to the five fingers on the original hand with 3 fingers, ignoring the 2 you are holding up on your other hand.
