Modern Japanese mahjong tiles are made of a synthetic nylon material with the symbols for the suit numbers, winds and dragons stamped onto the face of the tiles. The face of every tile in a set can be distinguished not only by the design that you see, but also by the design that you can FEEL when you rub your thumb across the face of the tile! And rub his thumb across the face of the tile is what many an expert Japanese player of mahjong likes to do during the course of a game! Yes, many an experienced player has developed the ability to "read" tiles with his thumb by rubbing it across the tile face and feeling the indentations. It takes hours of practice to get to the point where you can accurately distinguish each of the 34 different tile faces of a standard Japanese mahjong set with your thumb, and there seems to be little advantage in being able to do so. It is a diverting party trick and it also adds some kudos to a player's game if the player can pluck a tile from the wall, announce what it is and discard it without so much as glancing at it.
Mahjong is most exciting when played swiftly, so being able to read a tile without looking at it may be said to help the cause of speedy play, but apart from that there does not seem to be much practical profit in taking the trouble to learn the skill. However, in one instance that I can think of some small advantage could be gained about an opponent's tile by use of the "thumb-reading" technique. Experienced mahjong players enjoy playing a fast-paced game so if one player hesitates before discarding a tile, the player to his right is likely to have reached for "his" tile on the end of the wall before the first player has discarded. By placing his thumb under the tile in readiness to lift it off the wall, a competent "thumb-reader" would be able to read the tile while waiting for his turn.
But then, when the player on his left discards a tile, if another player claims it as a "Pon" the "thumb-reader" would not in fact draw the tile from the wall and it is more than likely that the tile will go to a different player. In that case the "thumb reader" will know what the tile is and will perhaps pay attention to where it is placed in the other player's hand. Some people might object that such a practice is a form of cheating, but others counter that it is just part parcel of the Japanese approach to the game. Of course that is not to say that the player who took the tile from the wall cannot resort to some deceptive tactics of his own by adding the tile to a random place in his hand while appearing to concentrate on placing it carefully into position so as to mislead the "thumb-reader" as to the construction of the hand. Whatever you may think about the practice of "thumb-reading", the fact that it is possible to do at all is testimony to the sensitivity of the human thumb, or "oya yubi" as it is called in Japanese.
As well as writing about Japanese mahjong, playing Japanese mahjong, dreaming about great mahjong victories and having nightmares about even greater disasters at the mahjong table, David Hurley runs Japanese-Games-Shop.com, a website dedicated to shipping exclusive Japanese mahjong sets and other Japanese gaming equipment, not to mention manga, and other gear direct from Japan to a select clientele of Japanese culture nuts all around the world.