[Bbradley62]

I guess I still don't understand how The Law works... Why doesn't North compete directly over West's double? Having already passed at that point, why does North take us past 4♠?

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[barmar]

In this auction, GIB believes bidding over the double would be a game invitation, just showing 12 points.

The reason it bid over 4♥ is apparently because of your double of 4♦, showing a good diamond suit. The book bid is pass, but the big double fit suggests competing.

[Bbradley62]

So, when I showed "real" diamonds, without showing additional values, North's hand improved from less-than-game-invitational to slam-invitational?

[barmar]

Two 9-card fits, a singleton in the opponents' suit, and two aces is a pretty powerful combination.

As usual, it concluded this from simulations. Was this a MP tourney? It was twice as likely to bid 5♦ at MP than IMPs in my simulations.

[Bbradley62]

It was matchpoints. Please remember that I'm mostly interested in (what I think is) the inconsistency of passing early and then voluntarily bypassing 4♠.

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The reason it bid over 4♥ is apparently because of your double of 4♦, showing a good diamond suit. The book bid is pass, but the big double fit suggests competing.

I like the fact that North bid over 4♥; I just would have wanted him to bid 4♠.

At another table, South opened 1♣ and North went to 4♠ earlier, when he should have thought he was less likely to have a double-fit.

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[barmar]

If South doesn't double 4♦, North does bid 4♠. The double is what gives it the idea to look for slam. Most of the hands it thinks South has have a good 6-card suit, so there's a likely 10-card fit there.

[Bbradley62]

ok. we appear to be talking in circles. maybe an innocent bystanding will sort it out.

But, the answer to my first question is that North didn't bid 3♠ over West's double because that would have shown 12 total points?

[barmar]

Yes, that's correct.