My recall of the database was 100% in <40 br="br" seconds.="seconds.">40>
After two months hiatus I decided to test the recall of the positions. It turned out that my recall was about 72%. With very little repetition I could improve that to 100% again.
When I stored the problems the first time in my memory, I focussed on storing the critical elements as diagrams. When recalling the positions now, it turns out that about 60% I remember as move sequences, while 40% are rememberred as geometrical patterns. The patterns in the form of diagrams show transfer to my actual OTB games, while move sequences are downright useless.
So tactical sharpness has reentered my OTB games again, but not to the extend that my rating rises to 2000. This means that I'm now obliged to announce officially
"Adult chess improvement is not as easy as I thought!"
In a private e-mail to mr. Z. I even admitted that there is no such thing as a supertrick in chess development.
That being said, I was left with the problem to explain "why does the fact that a 13 year old girl which hasn't have a coach, who is dislectic and can't spell "Nimzowitch", who is out of book at move 3, who's IQ is 30 points lower and who hacks me off the board in 23 moves feels as if she is using a supertrick?".
At the moment I'm reading "Chess, the mechanics of the mind" from GM Helmut Pfleger en IM Gerd Treppner. A book that is build on the ideas of De Groot et al.
This book gives an answer what it is what makes a grandmaster stand out in comparison to the amateur. There are a lot of things in which a grandmaster is slightly better than an amateur, like chess memory, depth of calculation, speed, visualization etc., but these are mere side effects. None of these areas make a decisive difference. The real difference is not based on a skill in which the grandmaster is better.
The real difference.
A grandmaster knows what he should not think about. He excludes a whole range of subjects when he is busy with a position. All other skills derive their power from this very fact. If you don't think about irrelevant matters, you speed up enormeously in comparison to who does.
If you don't think about irrelevant matters, your mind is not overloaded. With a mind that is not overloaded your visualization improves.
The supertrick is the ability to exclude irrelevant thoughts.
This explains a lot of observations from practice perfectly well. It explains why I think there is something special when playing against a child prodigy. The last 14 years I have searched for a positive skill. But it is in fact a negative skill. Hence I couldn't find it.
Another statement of the book is that there are no new ideas to discover for a grandmaster. In stead he works with a plethora of combinations of known ideas. I already suspected that, but it is good to see it confirmed. That is a very important statement, since it can provide a clue about what you should exclude from your thinking. If you think that the knowledge is endless, the possibilities are endless and your thinking about a position will be endless.