A very interesting article from the most recent New Yorker about the Bridge cheating scandal.
Besides detailing the scandal, it goes into detail about the tells/reads/nonverbal aspects of Bridge. Here’s one paragraph talking about this aspect of Bridge:
“Expert poker players often take advantage of a skill they call table feel: an ability to read the facial expressions and other unconscious “tells” exhibited by their opponents. Bridge players rely on table feel, too, but in bridge not all tells can be exploited legally by all players. If one of my opponents hesitates during the bidding or the play, I’m allowed to draw conclusions from the hesitation—but if my partner hesitates I’m not. What’s more, if I seem to have taken advantage of information that I wasn’t authorized to know, my opponents can summon the tournament director and seek an adjusted result for the hand we just played. Principled players do their best to ignore their partner and play at a consistent tempo, in order to avoid exchanging unauthorized information—and, if they do end up noticing something they shouldn’t have noticed, they go out of their way not to exploit it. Unprincipled players consciously take advantage of such information. And, occasionally, they go a great deal further than that.”