[jallerton]

Isn't the fact that RHO choose to accept the 3♠ bid authorised information? That suggests to me that he would prefer to defend game rather than a part score, hence making a 4♠ bid more attractive.

[lamford]

 jallerton, on 2015-March-06, 15:41, said:

Isn't the fact that RHO choose to accept the 3♠ bid authorised information? That suggests to me that he would prefer to defend game rather than a part score, hence making a 4♠ bid more attractive.

It is also authorised that he chose to accept it knowing that if he did not the person making an IB would correct to 4S. His only chance to keep us out of game was to accept 3S; however LAs are not determined with reference to the opponent's actions. We should poll say 10 people, playing the same methods (and the only legal agreement of the raise of 3S to 3S is "no agreement") and of the same ability, and establish whether they bid 4S or not; we do tell them that 3S was accepted, of course. I cannot imagine anyone passing. We do not tell them, of course, that partner tried to change it to 4S.

[campboy]

 jallerton, on 2015-March-06, 15:41, said:

Isn't the fact that RHO choose to accept the 3♠ bid authorised information? That suggests to me that he would prefer to defend game rather than a part score, hence making a 4♠ bid more attractive.

I think the fact that RHO accepted 3♠ is authorised, but that information alone doesn't necessarily help. We can't tell from AI whether RHO accepted the IB to stop partner substituting 4♠ or to stop him substituting a pass -- only the UI from partner's withdrawn call tells us which. (I agree with Lamford, though, that pass isn't an LA whatever.)