 Martin Nowak and Karl Sigmund offer a further variation that results in an even more surprising level of cooperation in the Prisoner’s Dilemma (Nowak &amp; Sigmund 1992). The reactive strategies outlined above are communicatively perfect strategies. There is no noise in “hearing” a move as cooperation or defection on the other side, and no “shaking hand” in response. In Tit for Tat a cooperation on the other side is flawlessly perceived as such, for example, and is perfectly responded to with cooperation. If signals are noisy or responses are less than flawless, however, Tit for Tat loses its advantage in play against itself. In that case a chancy defection will set up a chain of mutual defections until a chancy cooperation reverses the trend. A “noisy” Tit for Tat played against itself in an infinite game does no better than a random strategy.