Information gain from discarded tiles in Mahjong

Question

What information do you gain when another player discards a tile apart from seeing which tile it is? In particular from the position from which the tile is discarded. I neglect the timing side-channel in this context.

You can sort your tiles, but no good player will do that, since it increases the information your opponents gain while giving you no advantage.

As I understand the rules at http://mahjong-europe.org you can't regularly shuffle the tiles. In particular not between taking and discarding a tile.

From this I conclude you can find out in which turn the discarded tile was drawn(all initial tiles count as a single turn), but nothing more.

Is that correct, or did I miss a way to gain additional information, or hide information about when the discarded tile was drawn?

Answer 1

Like you said, you can't shuffle your tiles at will, but if I'm remembering correctly, you can put the tile you just drawn anywhere in your "hand", so you can't know when the discarded tile was drawn (at least not if you haven't a perfect memory ;) ).

However, each player has his own discard location, so you can easily see all tiles he has already discarded and maybe find a pattern in his discards which may prove useful to guess what he is waiting.

A player which is always discarding quickly the tile he just drawn is also a strong indicator that he is close to finish.

Answer 2

In all types of mahjong except Riichi-mahjong, the tiles are discarded into the pool at the center, usually in no particular order. If you have a very good memory, you can remember what tiles were discarded by whom. From this, you can gain information about what kinds of hands your opponent might be going for.

For example, if your opponent discards a 5 of circles and a 6 of circles in two consecutive turns, you can assume that it is very likely that they're going for a hand consisting of few circle tiles, an outside hand (terminals and honors in every set), or something similar. However, this depends on the style of mahjong you are playing.

To get more information about your opponent's hand based on the their discards, it is usually best to familiarize yourself with the types of hands that can win, and the point values associated with each hand. Then, you can deduce the kinds of tiles in your opponent's hands based on the discards that you see.

Just keep in mind that a good opponent could also be attempting to trick you, so while the likelihood of the tiles in their hands swings one way, it's not definite.

Answer 3

Generally, most people will organize their tiles in some fashion.

By watching both were they put the drawn tile, and where they pull their discard from, you can draw inferences on what they have in hand.

By looking at their set of discards, coupled to their hand organization you can often tell if they've changed hand goal mid-hand. (For example, starting off going for a set of 3 chous and a pung, and deciding instead to start grabbing matches, instead.

Further, you need to keep an eye on the discards to prevent yourself from trying to make pungs from numbers which already have been discarded twice (tho' that's basic to mah jongg, many novices overlook that). Often, I've found novices will hold a couple single tiles in order to make a specific combination hand, waiting to draw a second and take the 3rd from a discard, only to show grave disappointment when someone else discards the 2nd tile; it's not uncommon for them to visibly react, then discard the same tile. The more frustrated their look, the more likely they are working some fixated strategy and/or are close to going out.