At Howick Bridge Club, Psyches are strongly discouraged Monday nights and both Daytime sessions.
A psyche is a deliberate and gross misstatement of honour strength or suit length. The key words are deliberate and gross. If your partner opens 1NT and you respond 2H on a singleton because you had forgotten that with this partner you don’t use transfers then that is a mistake, not a psyche. Likewise if you choose to open 1S holding 5 spades and 9 points then that is not a psyche as it is not a gross misstatement of honour strength.
A typical psyche is used when you strongly suspect that it is the opponent’s hand and you are trying to disrupt their bidding. For instance, opening third in hand with only 4 points or perhaps bidding 1S after your partner has opened 1H, when holding few spades and lots of hearts to stop the opponents competing in that suit.
Psyching is legal and it does add an extra element to the game, but excessive psyching can cause problems, particularly when partner begins to half-expect them in certain situations, thus creating implicit partnership agreements.
Persistent psyching is not permitted.
Two deliberate gross mis-descriptions by a partnership in one session is evidence of persistent psyching.
Tony Haworth (Welsh Bridge Union) commentary on the most important changes.
Law 23. Comparable Calls - And Their Consequences
Law 26B. Lead Restrictions – Replacement Text
Law 31. Bid Out Of Rotation