5 ms·

Orienting the cards vertically or horizontally would count as communication, wouldn't it? Otherwise this would be trivial.

Fry-kun 10y ago
There are so many potential hidden channels! If 2nd can see what the 1st one guessed -- that's also easy Or if they just agree on the timing of the guess..
cwilkes 10y ago
I'm not sure how orienting the card that is on your own head would help. You don't know what it is. That being said the method of "Bob always tells the truth, Alice lies" is sort of a card orientation way for two people. Alice puts her card up sideways and Bob knows that to mean he should tell the truth. Likewise Bob doesn't rotate his and Alice knows to lie. However that only works with two people and they have opposite spins. Maybe it can work with more than two and you have two rounds of guessing. Also you need to know that you have differing spins.
- flashman 10y ago
  You orient the card based on the other player's card, for their benefit. That's why I think it would be against the rules - it's the same as if you held up fingers or made a face, it's communication. Bruce and Ava decide to put the card horizontally if they see a red card, or vertically if it's black. If Bruce sees a vertical card, he knows Ava sees a red card on his head. In the game of four, the players decide one of them will guess, and two others will communicate information in binary: horizontal, horizontal: hearts horizontal, vertical: diamonds vertical, horizontal: spades vertical, vertical: clubs However this latter method only requires three players, not four. But it is similar to how professional bridge players cheat, by communicating their hand (which is hidden from their partner) with secret signals: http://www.newyorker.com/magazine/2016/03/07/the-cheating-problem-in-professional-bridge http://www.newyorker.com/magazine/2016/03/07/the-cheating-pr...
  - cwilkes 10y ago
    Wow, thanks for that link about cheating in bridge. Spent hours going over that and stories on http://bridgewinners.com/ http://bridgewinners.com/

Fry-kun 10y ago

There are so many potential hidden channels! If 2nd can see what the 1st one guessed -- that's also easy Or if they just agree on the timing of the guess..

cwilkes 10y ago

I'm not sure how orienting the card that is on your own head would help. You don't know what it is. That being said the method of "Bob always tells the truth, Alice lies" is sort of a card orientation way for two people. Alice puts her card up sideways and Bob knows that to mean he should tell the truth. Likewise Bob doesn't rotate his and Alice knows to lie. However that only works with two people and they have opposite spins. Maybe it can work with more than two and you have two rounds of guessing. Also you need to know that you have differing spins.

flashman 10y ago
You orient the card based on the other player's card, for their benefit. That's why I think it would be against the rules - it's the same as if you held up fingers or made a face, it's communication. Bruce and Ava decide to put the card horizontally if they see a red card, or vertically if it's black. If Bruce sees a vertical card, he knows Ava sees a red card on his head. In the game of four, the players decide one of them will guess, and two others will communicate information in binary: horizontal, horizontal: hearts horizontal, vertical: diamonds vertical, horizontal: spades vertical, vertical: clubs However this latter method only requires three players, not four. But it is similar to how professional bridge players cheat, by communicating their hand (which is hidden from their partner) with secret signals: http://www.newyorker.com/magazine/2016/03/07/the-cheating-problem-in-professional-bridge http://www.newyorker.com/magazine/2016/03/07/the-cheating-pr...
- cwilkes 10y ago
  Wow, thanks for that link about cheating in bridge. Spent hours going over that and stories on http://bridgewinners.com/ http://bridgewinners.com/