Posted 2012-October-22, 15:10
If West started with J104 of hearts he should play the 10 on the second round. It's vital he give count here. That is easy.
If he had started with J10 doubleton you would still have had a guess, so...
In fact, to go back a trick or 2, with J104 of hearts on this particular deal he would have done well to switch to the 4 of hearts, again giving count at once (or at least when he plays the second one). On this deal, west is the one who knows that East probably has 5 hearts and they are only cashing 2 of them (if East were 5413 he would surely have doubled either 1D or 2D). But even if it weren't certain, playing 4 then Jack allowed East to know whether to overtake the second heart or not. (with, say, J84 west would here play 4 then 8).
You can't always afford to give a count switch (sometimes you have to play an honour to pick up a particular holding) but here you can.