Abstract

In contrast to Axelrod’s advice “don’t be envious” it is argued that the emotion of envy may enhance cooperation. TIT FOR TAT does exhibit a certain degree of envy. But, it does so in inconsistent ways. Two variants of TIT FOR TAT are introduced and their strategic properties are analyzed. Both generate the very same actual play as TIT FOR TAT in a computer tournament without noise. However, if noise is introduced they display some greater degree of stability. This is due to the fact that they form, in a prisoner’s dilemma supergame with suitable parameters, an equilibrium with themselves that is subgame perfect or (in case of the first strategy) close to subgame perfect. It is additionally argued that these strategies are exceptionally clear and comprehensible to others in that they conform to well known real live behavior patterns.