[TimG]

Compare these two non-competitive auctions:

1♣-1♦; 1♠-3N and
1♣-1♦; 1♠-2♥; 3m-3N.

Playing 4th suit forcing (to game), do you play that responder is showing different strength hands for these two sequences, or just that responder wanted to get a final bit of information before deciding where to place the contract?

Would your answer change if the auctions were:

1♣-1♥; 1♠-3N and
1♣-1♥; 1♠-2♦; 2♥/3♣-3N?

[FrancesHinden]

It's not a range difference, it's more a matter of certainty.

When responder jumps directly to 3NT without using FSF, then she is saying that she is confident 3NT is the right place to play, and opener needs a fairly extraordinary hand to look for a different game (opener may have a slam try).

When responder goes via FSF, then she was, at least at that point, interested in alternative contracts. Which contracts they were depends a bit on opener's rebid over FSF. The simplest auction is e.g.

1D - 1S
2C - 2H
3D - 3NT

when most likely responder was interested in playing in a spade fit.

Exactly what inference you take from the delayed route to 3NT is not an easy question to answer, because it depends so much on your FSF agreements:

- what is opener's default bid on the 'nothing' hand (5422 no stop, no honour in partner's suit)
- what does it mean if responder re-fourth-suits over opener's rebid (some play that as natural, others as neutral, forcing, asking for more information)
- if FSF is FG, what does it mean if opener jumps over the fourth suit?
- to what extent does opener rebid their own suit on a minimum 6-4 rather than introduce a new suit? e.g. after 1D - 1S - 2C - 2H - 3D, it's possible that responder has 4-card club support and was lurking to find out if you had a 9-card club fit, but does not have a strong enough hand to want to go past 3NT opposite a minimum.

So for each of your sample auctions I can tell you what I know about the source of responder's "doubt", but it may not be the same in your partnerships.

[P_Marlowe]

Yes.

If he was looking for a stopper, and says the round
later, he does not care, if I have one, this surely
affects the strength, ... well nobody likes it anymore
the "fast arival" principle, but it is a good one.
It makes the bid a king heavier.

With kind regards
Marlowe

[peachy]

The slow route initially "wants to go slow" for reasons only known to the slow route taker - means that strain and level investigation in his opinion needs to continue. It could be because of slam interest, because of stopper worries, or because he is looking into possibility of playing in a major, game or slam. The fast route shows that he is certain that "as far as he is concerned, 3NT is best" and also denies slam interest.