Strict dominance
One strategy pays more than another against every possible choice by the others.
Often misread asPlaying a dominated strategy anyway because the outcome where both players do so looks better for both, and concluding that game theory has misunderstood people.
How to see it
Better in every single case, so you never need to guess
One of your options is strictly dominated if another option of yours pays more no matter what anybody else does. You do not need to predict the other player in order to rule it out. The comparison happens entirely within your own choices.
The checkA better joint outcome is not a reason to pick a worse personal one; the comparison is between your two options with the other player held fixed, not between two outcomes.
Try itHold your opponent's choice fixed at cooperate and pick your best reply. Now hold it fixed at defect and pick again. If you chose the same thing both times, there is nothing you could learn about them that would change your mind.
Games that show it
Know these first
Leads on to
Easily confused with
Sources
- von Neumann, J. & Morgenstern, O. (1944). Princeton UP.