[BLML] The Monty Hall trap

Herman De Wael Hermandw at skynet.be
Tue Dec 14 12:32:39 CET 2010

Nigel is absolutely correct except for one minor quibble:

Nigel Guthrie wrote:
> [Nigel]
> Jerry has pin-pointed a difficulty.
> There are many tactical situations where some players deviate from system. For
> example
> - 3rd in hand openers.
> - 1H (X) bid.
> - 1N over-calls.
> - Interfering with opponent's strong artificial 1C/2C
> - Passing partner's pass/convert response in the the wrong suit.
> - Spurious trial/cue/exclusion bids.
> - "Game-forcing" calls on tram-tickets.
> The problem is that different partnerships have different favourite situations
> and hand-types; and some never "psych" at all.
> Regular "psychs" in a regular partnership aren't true psychs. Even if only
> occasionally used, they are probabilistic conventions.

A good name, which however does not help us any. Since every single 
psyche has a certain frequency (even if partner does not precisely know 
what the correct frequency is, he could be aware of it and so it should 
be made known to opponents), every psyche is a probabilistic convention.

I believe it is better to name probabilistic conventions: psyches.
Then we can make a distinction which Nigel does not yet make: those 
probabilistic conventions that are systemically catered for, and those 
that are not - psyches in other words.

> The disclosure problem is that:
> - Partnerships convince themselves that these are true psychs; hence not
> disclosable.

Partnerships should know better. But this is not a problem.

> - Partnerships defend their personal idiosyncratic "psyching" propensities as
> "general knowledge".

Which sometimes is true.

> - Partnerships feel that they *cannot disclose* these understandings because the
> agreements would be illegal. For instance, there may be strength requirements
> for opening bids; or "Random" bid agreements may be banned; or non-symmetric
> methods may be banned (some partnerships comprise a straight man and a
> comedian).

Which is why these "agreements" should not be illegal.

> Manifestly, undisclosed, such agreements are illegal.

And this is where Nigel, again, makes the common error. The 
non-disclosure does not make the agreement illegal. It merely creates a 
MI situation, which the TD will rectify if the opponents are damaged 
through the non-disclosure.

By continually labelling psyches as "illegal", the average TD (and many 
above average) feels that the psyche, when not disclosed, should be 
changed into a 40% AS. Rather, he should treat the non-disclosed psyche 
as any other MI, and ask himelf (and the opponents) "what would 
opponents have bid if they had been told that this player psyches this 
bid, with this particular hand, about 5% of the time". Most often, they 
would not have acted differently.

> This problem would be mitigated if system-restrictions were scrapped, because
> partnerships would then be more ready to admit to such understandings.

That too is a problem. Most Directors believe that the system regulation 
regarding light openings are very strict: "if you do it, and there is 
even the slightest doubt that you have doe it before, then your 
agreement is a banned one". That cannot be the correct interpretation of 
a piece of system regulation, as that would be tantamount to the 
well-known ACBL rule: "it's OK to psyche, provided you never do it".

Herman De Wael
Wilrijk Antwerpen Belgium

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