Investigating dominated strategies

Selecting Tools ‣ Dominance toggles the appearance of a toolbar which can be used to investigate the structure of dominated strategies. Strategies can be eliminated iteratively based on whether they are strictly or weakly dominated.

When the dominance toolbar is shown, the strategic game table contains indicators of strategies that are dominated. In the prisoner’s dilemma, the Cooperate strategy is strictly dominated for both players. This strict dominance is indicated by the solid “X” drawn across the corresponding strategy labels for both players. In addition, the payoffs corresponding to the dominated strategies are also drawn with a solid “X” across them. Thus, any contingency in the table containing at least one “X” is a contingency that can only be reached by at least one player playing a strategy that is dominated.

Strategies that are weakly dominated are similarly indicated, except the “X” shape is drawn using a thinner, dashed line instead of the thick, solid line.

Clicking the next level icon removes the strictly dominated strategies from the display.

The elimination of multiple levels can be automated using the fast forward icon, which iteratively eliminates dominated actions until no further actions can be eliminated. The rewind icon restores the display to the full game.