I asked my expert panel --- Your Left Hand Opponent (LHO) opens 4 and your partner doubles. Your understanding is that the double is not a penalty double. What are the minimum hands you would need in order to pull the double? What difference would vulnerability or type of event make?

There are three reasons to bid over 4 doubled. They can make 4 and you have a good save. You can make something at the five or six-level. You can’t make anything but you push them up. There are two reasons to pass 4 doubled. You can beat them and can’t make anything at the five-level. Letting them make 4 doubled is better than bidding at the five-level, getting doubled, and going for at least 800. Sometimes there’s no correct solution. If you pass they will be +790, if you bid you’ll be minus 800.

Point # 1: Pass the double with balanced hands.

Marinesa Letizia: Most balanced hands I pass. I need a long suit to pull or two places to play, so that I can bid 4NT saying I have two places to play. Pretty much the same at all forms of scoring.

Barry Rigal: Obviously we all pass with trump tricks. I pass when balanced 4333 or 4432 or 5332 with the expectation of scoring more then in our side’s contract, or when my best hope of going plus is to defend and hope to scramble four tricks. With a one-suiter I'd need side shape to bid; 6331 I probably act. A hand like xxQxxxKJxxxxx is delicate; I tend to remove to 4NT here. That is on the cusp. Take away J or make it J and I pass.

Point #2: Some experts bid only when they expect to make a plus score. 

Henry Bethe: I would pull when my strength was such that a five-level contract seems certain and a slam is possible, or with extreme distribution, such as 6-5 or a seven-card suit, which might reduce the defensive tricks available. After 4 - double - Pass, I play 4NT shows playability in at least two suits.

Point #3: If you’re going to pull, you should have understandings about how to get to the best strain. 4NT should show at least two suits and asks doubler to bid his lowest suit. If you have a very good hand you can bid 5, a slam try asking doubler to bid a five-card or longer suit. Doubler can then hedge with 5NT denying a five-card suit.

Point #4: When in doubt, pass the double when holding a doubleton spade.

Mike Passell: My feeling in general if it is close, to pass with two spades and bid with one or three. This is of course a general rule as distribution comes into play. Many times at unfavorable it is right to pass unless an action is very clear as if you are wrong and they make it - or overtricks - it could still be your cheapest minus. On the other side of the coin I have had much more success bidding in direct seat instead of doubling with big hands where double would seem like a choice xAKxxKxAKJxxx, I prefer bidding 5 as we might make it opposite many flat hand where partner might be passing and collecting 100 or 300 or going minus 590.

Joe Kivel: In general, after partner doubles 4, I bid on virtually all six-card or longer suits, all 5-5's, and on most semi-balanced 12+ point hands with at least ten points outside spades. The exceptions can be when holding the kiss-of-death doubleton spade. Partner's hand shouldn't be too shapely, since he had a 4NT takeout bid available. With the semi-balanced hands, vulnerability makes a difference. I am more apt to pass when non-vulnerable.

Point #5: Pass if you think that bidding will lead to a large minus score. –790 is better then –1100.

Jill Meyers: I would need either enough HCP that I think we can make a slam or distribution (at least a six card suit). I would sit on a 4-3-3-3 Yarborough, since if they make it, our number from bidding would be greater. Type of event doesn't matter.

Some players would always pull assuming they don’t have a spade stack.

Marty Bergin: I would pull holding -xxxxxxxxxxxxx. If opponents are vulnerable I am FAR more likely to pull.

Chip Martel: Mostly am bidding to make or have significantly more offense than defense. So bid on almost all seven-card or longer suits, most six-card suits  (unless a weak suit with side honors, or a slow spade trick). With a five-card suit rarely bid unless 5-5 or a pure 5-4. Also, if non-vulnerable versus vulnerable, I’m much more likely to bid since the 4-bidder usually has it, and I’ve more to gain even if I go down. Holding a stiff spade (or void) is positive for bidding, holding a doubleton is worst.

Bobby Lipsitz: I think mainstream expert treatment is that the double shows mainly convertible values. Not a penalty double, but also not for takeout unless bidding primarily to make. So I’d pass the double with xAxxxxxxxxxxx, bid 4NT with xAxQJxxxQJxxx.

Point #6: Unless you’re playing with Kit Woolsey who plays penalty doubles, you can’t double 4 holding KJ10xAxxxxxxxx. Partner is very likely to pull your double. Pass and hope partner reopens with a double.

Bart Bramley: I'm an extremist on this one. Many years ago, after a succession of -790's and -590's, I deduced that pulling was frequently right, certainly in the majority of marginal cases. I wasn't necessarily expecting to make what I bid, but I was pretty sure that the opponents were going to make what THEY bid. My results have been very good (I can't say perfect) with this philosophy.

The most important feature is the NUMBER OF SPADES. With zero or one, pulling is automatic, even with xxxxxxxxxxxxx. With two, pulling is usually right, unless the holding is AK or KQ or something similar. With three I will more often sit, but I would still usually pull to a six-bagger or if I had 5-4 in two other suits.

A secondary point is that partner can't double with random strong notrumps, unless he is prepared to see me bid. The more spades partner has, the greater the chance that I can't sit. Bidding has many ways to win. The obvious ones are (1) making what you bid, and (2) finding a good save. But also there are (3) pushing the bad guys up to where you can set them and (4) reaching a good slam.

I recall a great example from a late-round team-trials match a few years ago. Two famous players had (approximately) xxJxxJxxxJxxx and faced this problem. One of them passed and went -790 (double-dummy defense could have beaten it). The other player bid 4NT, reached a 5-4 diamond fit, and escaped for -200, to win 11 imps in a match that was decided by that very amount. 

Bobby Wolff: With almost all balanced hands holding 14 or fewer points, I pass. The exception being xxxAJ10xKQxxKx and vulnerable vs. nonvul where I would bid 4NT, because of the prime values, and convert 5 to 5. But with a good, reasonably long suit particularly hearts, I bid. With xxxAJ10xxxJxxx, I bid 5. Without hearts, xxxxAJ10xxxKxx I bid 5. Holding xx in hearts and Qx in clubs instead of the 3-1 distribution, I would probably pass.  

Much of it has to do with one's opponents.  If a very gentle lady or an older gent was the 4-bidder, I would respect their hand much greater than I would a young up-and-coming whippersnapper. And, of course, tend to take out my partner's double.  

Summing up, this type of bridge question embodies a strong poker element into our bridge game. Very little is right or wrong and the only important thing to consider is being right on that particular hand. When you and your partner are actively ethical, something we should all strive for, it is one of the prices straightforward players have to pay.

Larry Cohen: I need either a) extreme shape or b) possibility our side has a slam. With a bad hand (say, 0-7 HCP) I'd pull only with at least a six-card suit - and even then probably not a 6-3-2-2 hand. If opponents vulnerable, I'd be more likely to pull - I find that vulnerable 4 openers (especially if unfavorable) are quite sound and often make.

Point #7: Vulnerable 4 openers are more apt to make then non-vulnerable 4-openers.

Bill Pollack: Double is not "penalty", and 4NT is, of course, pure takeout. There's lots of ground to cover between the two. My minimum pull is more based on shape than HCP. I would certainly bid with -any- non-hopeless six-card suit, i.e. 5 with xxxxxxxQ10xxxx. Vulnerability makes some difference, since I'm more likely to play for penalties if they are non-vulnerable, since vulnerable 4 bids are supposed to be pretty good. With a five-card suit, I need both a reasonable suit and some values to bid especially if they are not vulnerable -- perhaps xxxKQxxxxxxxx is minimum.  At matchpoints, where going plus is so important, I sit a bit more.

Bob Hamman: With a spade void or any strong two-suiter, my tendency is to bid 4NT or pass. If I have a more balanced hand I tend to double. I need to see some offensive potential to pull doubles.

Kerry Sanborn: In my own favorite partnerships, I play that double direct is takeout. The level starts too high for accuracy, however. Your partner has the tool of 4NT available to make sure that you bid a suit, so double is more penalty than that. I think that in order to sit the double out, you need no fit or a reasonable expectation of going plus and defeating 4 doubled. Given a hand such as xxxQxxxJxxQxx, it would not occur to me to bid a suit when partner doubles for takeout. I have to have a good expectation that I will do better by pulling than by passing. For example, given xxxKxxxxQxxxx, partner could fit either minor, so I am happy to takeout with 4NT myself. Vulnerability counts too. If I am vulnerable against not, I might decide that -590 or -690 looks better than -800 or -1100. Preempts work. The average player should use them more often and discuss with his partner what their partnership should expect at the various vulnerabilities.

Jon Wittes: I would tend to sit for the double on nearly all balanced hands, unless I had so many points that I felt we were odds on to make a slam. Even then, I would tend to sit at all but unfavorable vulnerability. On unbalanced hands, 5-4-3-1 minimum distribution, I would be more inclined to consider bidding, the more distributional, the more I would be inclined to bid. I would also be more inclined to bid at matchpoints, if I thought we were a favorite to make our contract at the five-level, and they were a favorite to go for less than the value of game. At IMPs, I would be less inclined to bid, since the difference between +300 and +400 or +450, or +500 and +600 or +650, is so minimal when compared with the risk of bidding at the five-level and going down. I would also be more inclined to bid in an IMP event, when we are down a significant number of IMPs, and need a swing our way. 

Eddie Kantar: I would pull with the expectation of making something so I would be distributional, perhaps a reasonably strong two or three-suited hand or a strong six or seven-card suit as partner does not promise support for all the unbid suits, but figures to have at least three cards in the unbid major. You must keep in mind that partner thinking you have something might up the ante and bid six! More often than not, one passes 4 doubled.

Some players always sit. Playing penalty doubles work when you have KJ10xAxxxxxxxx. But what do you bid holding xKQJxKQJxAKxx? If you have to bid 4NT with this hand, you deserve to find partner with xxxxxxxxxxxxx or QJ10xxxxxxxxxx. If you double for penalties withxKQJxKQJxAKxx, you deserve to find partner with xxAxAxxxxQJxx. From my experience, the takeout type hand occurs much more often then the pure penalty hand.

Kit Woolsey: Sorry, but my understanding is that the double IS a penalty double. Of course partner might just have a good hand, but he might also have a trump stack. I need something pretty extreme to pull to five over four. A so-so six-card suit and a stiff spade is not enough - I would sit with that. With a spade void or a strong six-card suit I might pull, but then only might. Vulnerability and type of event are irrelevant here.

Conclusion: There’s no iron-clad method of bidding over 4 doubled. Since this is a bidder’s game my final thought is - when in doubt bid.