Liar's Poker and Liar's Dice

Liar's Poker is played with the serial numbers on dollar bills: each player looks only at their own bill's digits and makes escalating claims about how many of a given digit exist across everyone's combined bills — for example, "there are at least three 7s" — with each subsequent player either raising the claim or challenging it. Liar's Dice works the same way with hidden dice rolls under a cup instead of serial numbers: players bid on how many of a given face value exist across all dice in play, bidding higher or calling "liar" on the previous bid.

Both games are built around the same core skill: making and calling bluffs about a hidden quantity using only your own partial information plus a read on how confidently the other player is bidding. That structure — private information, public claims, and a decision about when a claim has become too aggressive to be true — is why these games became associated with trading floor culture (popularized partly by Michael Lewis's account of Salomon Brothers) and occasionally surface in interview conversations as a way to probe how someone reasons under bluffing and incomplete information.

Worked example

In Liar's Dice with five dice each for two players, you look under your cup and see two 4s among your own five dice. The opponent bids "three 4s exist total." Since you already hold two of the required three, the bid needs only one more 4 among the opponent's five unseen dice — a reasonably likely event — so raising to "four 4s" (now requiring two more from their five dice, a longer shot) is a much riskier claim than simply calling the current bid true and passing, or raising by only the smallest safe increment.