How intelligent are Grayling(or I)

Hi, today I just returned from a angling trip where I experienced following,

After spotting two Graylings feeding on duns, just in front of a lib current, I managed to catch one( on a size 14 Royal Humpy 3.5 x tippet), casting from the right bank. I was an instant take, and the fisk mesured 36 cm(14.5 inches).

The seccond fish still feeding 1 m in front of the one I just caught, would not take any of my my dries.

4 ours later I returned, but now casting from the right bank, I now managed to catch the front fish on a size 14 Gold bead Hare's ear(nympf), it was also in instant take, but a bigger and stronger fish than the first one, and it mesured ca 43 cm(17 inches). For a Danish stream, Grayling this size is and older fish.

The following days, I was obserwing both of my new "friends" still feeding on duns or whatever, but it was impossible to make them take my flies again, no matter how hard i tried.

I am not an experienced Grayling expert, but it seems to me as these two fish had been able to learn, and if so, would that mean that they are clearly capable of telling the difference between atifficial flies, and original insects?, To be ohnest I think so, but fish
are sometimes triggered by there instincts to take our flies and lures.

I know this is an never ending debate, but nevertheless today, in year 2007, I still meet fly fishermen who believe in immitations. I fear that Interlectually we fly fishermen have not progressed mutch since Halford and G.E.M Skues(or Carl Richards and Doug Swisher for that matter), or maybe one should just go fishing as quick as possible, instead of thinking so mutch about a question that is more likely never to be answered.

Chers

Morten.