False Carding or please don’t confuse me

John Wood left an interesting comment on my blog on restricted choice.   He gave an example of a false card:

Here it is 

…………………………………………………

Suppose you have

KQ2 opposite A9863

You cash the King (or Queen) in dummy and the person on your right(East)  plays the Jack.

Do you run the 9 next time, based on restricted choice (if they had had the 10 they might have played it)? 

………………………………………………..

If you started life with J10x and declarer cashes the King in this suit then it can’t hurt to play an honor (the jack or the ten). But in the example given here declarer will soon find out about the false card since their next play would be to cash the Queen and you have no reply to that one. So let’s change John’s example a little bit.

You have

K2 opposite AQ9863 and you need all the tricks in this suit. You cash the king and the jack drops. Should you play for the finesse on the next round or should you play for the drop. Here you are deciding if the jack is singleton or if East had the J10  or if East started with the J10x and was falsecarding. Suppose you know that East is a novice who would never think of falsecarding or East was the honest sort that thought falsecarding was “wrong” so you discounted that possibility. Then you would be in a restricted choice situation. East would be known to have the singleton jack or the J10 doubleton and since from the J10 doubleton he could play either card equally the singleton jack is more likely. But it is very rare that we are playing in this very special game where nobody ever falsecards.

So in most games the jack could also be from J10x. So East could now have the singleton jack, the jack ten  doubleton or the J10x. Even after west has played the x could still be one or two missing cards. But experience does tell us that even expert players do not always think of false carding so experience tells us that the J10x is less likely than it should be in a perfect mathematical world.  I suppose that in a high quality game I would probably not finesse but in many games I would. 

There are a lot of wonderful things to talk about when we introduce falsecards in the game. I must make sure never to tell my students about them. Too confusing for we experienced players!