Back in the early days of bridge there was the penalty double. However, people began to realize that it wasn't much use at low levels because you could rarely get rich even if they were psyching--they would just run to the real suit or otherwise escape justice. Thus the penalty double evolved into two clades: the penalty double and the informatory double (nowadays this is universally known as a takeout double).
It didn't take long for the takeout clade to further evolve into two sub-clades: pure takeout and "cooperative" doubles. The latter include all sorts of strangely named beasts: action, cooperative, competitive, etc. The general rule (not very well described in the literature) is that the higher the level, the more tempted partner will be to leave it in. This latter form is at its most useful in matchpoint bridge because, if you can catch them speeding and get them down one doubled and vulnerable, it will beat any part-score you might be able to have made.
I believe there are, however, two sub-clades of the penalty double:
- pure penalty: "don't take it out if you ever want to play with me again;"
- penalty-oriented: "you're expected to leave it in if you have normal distribution, nothing that partner doesn't know about."
Actually, this latter type is perhaps more common than you think. It occurs any time you bid a game, the opponents sacrifice and the player in direct seat doubles. That player can never be sure that defending a doubled contract is the par result. What he means by the double is this: "From where I'm sitting, it looks like doubling is our best shot. Feel free to pull if your hand is more offensively oriented than I think it is."
But it might not be a clear sacrifice. Such situations may be somewhat rarer, but they are not unknown. An example came up just the other day in a pairs event. I will give you my partner's hand and the auction first: ♠KQJ8432 ♥T3 ♦Q ♣K53.
Both sides are vulnerable. Admittedly, not everyone will open 1♠ but I think it's the right bid, provided that you're willing to be a bit flexible later on in the auction. LHO overcalled 2♥ and partner raised to 2♠. RHO upped the ante with 3♥ and you made a preemptive raise to 3♠, showing six or more spades and presumably a hand that is on the weak side for an opening bid. LHO doesn't go quietly and bids 4♥. Partner doubles and it's back to you. Your call?
What do we know about the auction? The opponents are a self-described pickup pair and their profiles suggest intermediate. Do you think they have their bids? They might have stretched a bit, but nobody bids this way without something pretty good. What about partner's double? Is it a penalty double? I think it is. One of the "rules" that I like to go by is that once we've bid our suit three times, any double is for penalty. What could we be taking out into, realistically speaking?
So, what to do? Partner has 8-10 hcp and exactly three spades. He will never try to get a penalty in this situation knowing that our side has 10 spades. It's likely that partner has a relatively balanced hand, too, because with a singleton anywhere, he's going to bid 4♠ if he's at the max end of his box (5-10).
How many hearts do they have? Almost certainly nine. With a stiff (as noted), partner would have bid 4 himself (or passed).
How many tricks to we have cashing? At most one spade and maybe a club. Partner should have a couple of sure tricks and maybe a third if he has AJ in, say, diamonds. Are we getting rich? At the very most, we might get 500 but 200 is more likely. Can we make game our way? Does partner have the spade ace? I think it's doubtful. With that card, and six points on the outside, I think double is an unlikely call. The spade ace will, essentially, be a bit of a waste, defensively speaking, given our own strong bidding in spades.
What about "the law?" The strength appears to be well balanced between the two sides which is important for the law. We don't have a pure hand with good shortness (can't count the diamond queen for both), so it's possible that the law will be off a bit. Maybe 18 tricks instead of 19? If this is the case, and if it turns out that both sides can make exactly nine tricks, we should defend. What are the other possibilities (using my guesses for the probabilities)?
- 20 total tricks (15% likely):
- Both sides make game: par score +620 (pull)
- We make an overtrick, they an undertrick: +650 (pull)
- They make the overtrick: par score -650 (pull--unless we want to be -990)
- 19 total tricks (50% likely):
- We make an overtrick: par score +650 (pull)
- We make game: par score +620 (pull)
- They make game: par score -200 (pull)
- They make an overtrick: par score -650 (pull as before)
- 18 total tricks (30% likely):
- We make game: par score +620 (pull)
- Neither side makes game: par score +200 (pass)
- They make game: par score -500 (pull as before).
- 17 total tricks (5% likely):
- We make game: par score +800 (pass)
- We go down one: par score +500 (pass)
- We go down two: par score +200 (pass).
Just looking at the probabilities and following the LOTT, it looks like we want to pass 15% of the time and pull 85% of the time.
Let's go back to partner's double. In the old days, we could distinguish between tentative penalty doubles and stand-up-on-your-chair-and-slam-the-red-card-down doubles (just kidding, of course). Is partner's double an absolute final decision? No, how can it be? The opponents have bid 4♥ strongly. They're not kidding around so they think they have a play for it. If partner has a heart trick coming, it must be available on offense, too. Why has partner doubled and not bid 4S himself? For the reasons given above: each side might have only nine tricks available, we almost certainly have to lose a spade and, likely, two hearts. Do we have the rest? Partner isn't sure. Basically, in this context, his "penalty" double simply says "I think this is our hand, I have a balanced hand, and they are probably going down." After all, it's very unlikely that opener is going to bid voluntarily again after this sequence. In other words, this is a classic POD situation.
It's decision time. Is there anything partner doesn't know about our hand that would justify pulling? Yes! We have a seventh spade!
Partner's (my) hand: ♠T97 ♥J4 ♦AT63 ♣AT98. Leading the ♦A or underleading a club would result in down two for 500 and a 45% board. Leading our suit should have resulted in 200 and a 28% board. Neither of these would be total disasters. As it happened, we didn't set the contract, resulting in a 0% board.
So, there were 18 total tricks on the board. Not playing double-dummy defense would have resulted in 19 total tricks.