Perfect information
Every player sees the whole history of play before choosing, so nobody is ever unsure which situation they are in.
Often misread asTaking perfect information to mean the players know everything relevant, including each other's payoffs, and so running it together with complete information.
How to see it
Everyone can see the whole history before they move
A game has perfect information when every player, whenever they move, knows exactly everything that has happened so far. Chess has it. Poker does not, and nor does any game in which two people choose at the same time.
The checkPerfect information is about the history of play; complete information is about knowing the game itself.
Try itClassify backgammon. The dice make the future uncertain, but every player sees every roll and every move before choosing, so it has perfect information. If you said otherwise, you were testing for certainty rather than for observation.
Games that show it
Know these first
Leads on to
Easily confused with
Sources
- Kuhn, H. (1953). In Kuhn, H. & Tucker, A. (eds), Contributions to the Theory of Games, Volume II, Annals of Mathematics Studies 28, Princeton University Press, 193-216.
- Osborne, M. & Rubinstein, A. (1994). MIT Press.