Is it ok to think?

[Free]

Imo it depends, but it's an unethical habit and rather not allowed.

 

IF you have to show partner if the lead is good, it's quite unethical to think at that point instead of when declarer is planning the play. If you can play ♦T or ♦2 quickly, you show your preference of the lead. However, if you think and then play a card, it shows the same preference but with a bit of doubt. Here it's clear that East doesn't know if the lead was good or not, but that doesn't give him the right to give his partner UI. It's a known problem with smith signals that sometimes players have to make an unethical thinking pause.

 

On the other hand, if you're not playing any smith signals, then what is there to think about? Well ok, you can just think if there's a useful signal somewhere, but it's still fuzzy to find a clear reason to think.

[mikestar]

On the facts cited, the hesitation is not OK Now if declarer had called the dummy's card instantly or after a perfunctory plan (say 5 seconds) then third hand must be given time to plan the defense, including but not limited to the first trick.