Reading Depth

The reading depth of a tactical analysis can be defined as the maximum number of moves one has to read before reaching a conclusion about a certain position.

Obviously, the depth of analysis depends on the knowledge or intuition of a player, which determines the level at which they can abort their analysis:

• Lee Changho, playing in the second game of the 6th GS Caltex Cup final ^[2], read the placement of the double ladder break at move 71 before playing the descent of L2 at move 39.
• Kitani Minoru read to a depth of 37 moves in the 2nd Top Position Tournament vs Sakata Eio, as related by Nakayama Noriyuki in The Treasure Chest Enigma.
• Nakayama Noriyuki in the game that earned him promotion to 6 dan professional read a critical fight to a depth of 20 moves ^[1].

The other important aspect of tactical analysis is reading width.

Example

Experienced  

For an experienced player the depth of analysis in this situation is zero or at most one. He knows that White can kill Black by playing at a.

Knowledge of eyes  

For anyone new to this situation, the depth of analysis is about 5: the number of moves to see that Black's seemingly making two eyes is fluked by the shortage of liberties.

No knowledge of eyes  

However, for a complete beginner lacking knowledge about two eyes, it is necessary to complete until capture:

corner  

In the worst case, this can take 13 moves, passes included.

Size of chunk

In Antti Tormanen's thesis on expertise reading depth corresponds to what he calls the "size of a chunk". The number of chunks one can evaluate would then correspond to the reading width.

[1] In Kage's Secret Chronicles Of Handicap Go by Kageyama, his opponent (Yokoyama) lays out a sequence of 24 moves and comments "if you can't read that out instantly, you can't call yourself a pro."

As both Nakayama and Kageyama demonstrate in the two books mentioned, there are 20 moves and there are 20 moves. Nakayama has several problems that require one to read dozens of moves and Kageyama states that one must practice ladders till they become trivial reading exercises. Because the usefulness of certain joseki variations depend directly on a ladder, we routinely read ladders of 50 moves in the opening. That is very different from reading 37 moves in which several tesuji appear.

[2] Lee Changho did this in the "domestic", Korean edition of LG Cup, which is now the GS Caltex Cup. The game is available on GoBase (account required). Lee's descent is 39 and the double ladder breaker is 71, 32 moves later. It's impressive reading and a short game, ending at move 81. Apparently due to the opponent not reading as deeply.