  The Rock-Paper-Scissors (RPS) game is a widely used model system in game
theory. Evolutionary game theory predicts the existence of persistent cycles in
the evolutionary trajectories of the RPS game, but experimental evidence has
remained to be rather weak. In this work we performed laboratory experiments on
the RPS game and analyzed the social-state evolutionary trajectories of twelve
populations of N=6 players. We found strong evidence supporting the existence
of persistent cycles. The mean cycling frequency was measured to be $0.029 \pm
0.009$ period per experimental round. Our experimental observations can be
quantitatively explained by a simple non-equilibrium model, namely the
discrete-time logit dynamical process with a noise parameter. Our work
therefore favors the evolutionary game theory over the classical game theory
for describing the dynamical behavior of the RPS game.
