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Paper Beats Rock

November means the International RPS Championship is about to occur...that's RPS as in the World Rock Paper Scissors Society.


Specific to mathematics, RPS is an example of a relation that is non-transitive. Note: In a transitive relation R, (a R b) and (b R c) imply (a R c). The relation in RPS is non-transitive because (Rock defeats Scissors) and (Scissors defeats Paper) but (Rock loses to Paper).

Some claim game theory strategies can be used to improve one's odds of winning. These range from documented tendencies of (1) beginners tending to use Rock when they are losing, (2) men using Rock in an opening game, and (3) women using Scissors in an opening game. To avoid probabilistic "leanings," serious competitors plan their moves in advance, basically as part of a script.

Source: Adapted from Stephanie Yu's "Taking Fun Seriously," USA Weekend, October 27, 2006