Obvious Shift Principle

(from A Switch in Time by Pamela and Matthew Granovetter)

When is the Obvious Shift Principle Applied?

At Trick 1, partner of opening leader compares the led suit and Obvious shift suit. Encouragement (upside-down or standard) denies tolerance for the Obvious shift suit. Discouragement actively confirms tolerance for the Obvious Shift suit. This applies whether opening leader will maintain the lead or not. More details below.

Rules for Identifying the Obvious Shift suit (in order of priority)

Implementation Details:

Requirements for Encouragement in Obvious Shift suit

if suit is:

To Call for an Unusual Switch...

Play an unusual honor card. However, opposite a lead from the top of an honor sequence, when dummy does not have a singleton (vs. a trump suit), an unusual honor shows the top of the next lowest sequence, to allow an underlead.

With No Real Preference... In general, this common situation is handled by making the least costly preference. This should be accounted for by opening leader, in the context of the hand. Sometimes, one can, say, with T82, under the Ace, play the 8 (denying tolerance for obvious shift), then follow with the Ten (denying a doubleton). This denies encouragement for both the led suit and the Obvious Shift suit, so this is the way to show either general indifference or perhaps encouragement for a 3rd reasonable suit. General Carding Scheme