Cooperative Slam Bidding
Bridge is a partnership game.
You hear people rationalizing bids all the time with something like "partner could have had..." Well, usually partner is better informed about what he has than you. Unless he has transferred captaincy and you have to make some kind of decision, that is not a good justification for making a (mis)bid. When in a cooperative auction it can be useful to think about what you have shown and what you have in context of that.
Nothing should illustrate this more than cuebidding sequences to try for a slam. Unfortunately, many times after one player has bid their hand they then bid make the decision to drive to slam themselves instead of trusting partner to do the right thing. This mistake probably costs most players thousands of imps in the long run.
Take the uncontested auction auction 1-2-2-3-4-4-4 in a 2/1 system that does not use serious 3N. Many people would describe 4 as a signoff. That is false, partner is still in the picture and can bid on. 4 is limiting your hand and merely says that you have made 1 slam try and that was all you are worth. You probably have something like a good 14 or 15. Partner can take control with keycard or pass. He also may cuebid again if he is not sure whether or not slam will make (yes knowing how many keycards partner has is not always the answer). The point is a very basic one in bridge; don't bid your hand twice. Still, psychologically people feel like over 4 it's do or die and they must make a decision. They will see their 14, think of some hands that partner can have where slam is cold, and try keycard. What they forget is that most of the hands where slam is cold partner is not going to pass 4.