How important is repetition for acquiring pattern recognition skills?

A bit more than one month ago, I decided to start to do some regular tactics training on the Chess Tactics Server (CTS). Using CTS to improve chess skills is still a hot topic in the chess blogosphere and a small but growing group of chess bloggers, most notably Temposchlucker, Transformation, and General Kaia, put a significant effort into solving tactics problems on the Chess Tactics Server. One attractive feature of CTS is the huge amount of available problems. On one hand, this guarantees variety. On the other hand, it (almost) prevents that problems have to be solved repetitively. Repetition, however, is considered as very important for transferring the knowledge of tactical positions to long-term memory. This raises the question, how useful is solving chess tactics problems with a very low repetition rate at CTS to improve chess skills?

Several scientific studies tried to address the difference between grandmasters and the common patzer. The huge skill differences between grandmasters and even good amateur players can be observed in simultaneous exhibitions. One grandmaster plays seemingly effortless against dozens of amateur chess players and wins most, if not all, of the games even though the grandmaster's thinking time is sometimes only few seconds per move! This immense difference in ability is attributed to the grandmaster pulling information about the positions out of his long-term memory, which is a very fast process, while amateurs have to analyze the position. The efficient use of long-term memory for a complex game like chess requires storage of a substantial amount of positions, or so-called "chunks", in the long-term memory. Many common techniques to memorize information base on spaced repetition: the information is memorized repeatedly until it is finally safely stored in long-term memory.

This method can be also applied to studying chess tactics. A set of tactics problems is solved over and over again until solving them becomes automatic - the solution is recognized on first sight without the need for analyzing the position. There is only one problem with chess: the number of possible chess positions is astronomical. Therefore, the brain has to rely on recognizing the most important features of the position instead of the position of each individual piece on the board. For instance, there are well-known tactical themes such as forks, skewers, etc. An individual position with a knight forking king and rook may be unique and may never repeat in any chessgame. The general characteristics of the position, for example that the forked pieces have to be on squares with the same color, are always the same. Therefore, it is not necessary to repeat individual positions to achieve the skill to play a knight fork. Playing through a large number of different problems where knight forks occur will also do the trick. But which approach is more efficient to develop chess tactics skills?

She short answer is: I don't know. People became chess grandmasters before the availability of databases or even books with large collections of tactical problems. Therefore, repetition of individual problems is definitely not necessary to acquire a high level of tactical skills. Individual problems are only rarely repeated during CTS sessions. Tactical pattern, such as the knight fork, however, are repeated. I speculate that the very low rate of repetition of individual positions together with repeated occurrence of specific patterns such as forks might actually be very effective for learning tactics because the brain is forced to learn recognizing the essential pattern instead of specific complete positions. Proving this, however, would require a long-term study with many players using a very controlled training regime, something that certainly collides with the pronounced individualism of chess players. For now, I can only say that I am making some progress with training on the Chess Tactics Server and I even see (or want to see) some positive influence of that in my games. But more about that in a later post.