The first and most fundamental type of multi-person social dilemma, a generalization of the Prisoner's Dilemma game to include more than two players, discovered simultaneously and independently in 1973 by the US psychologist Robyn Mason Dawes (born 1936), the US mathematician Henry J. Hamburger (born 1940), and the US economist Thomas C. Schelling (born 1921). It is an interactive decision involving three or more players who each face a choice between a cooperative strategy (2) labelled C and a non-cooperative or defecting strategy labelled D. The payoff structure is such that D is a dominant strategy for each player in the sense that each player obtains a better payoff by choosing D than C no matter how many of the other players choose C; but the outcome if all players choose their dominated C strategies is preferable from every player's point of view to the outcome if everyone chooses D. Apart from the Prisoner's Dilemma game, which is a special (two-person) case, the simplest example is the three-person game in which, if three players choose C, then each gets a payoff of 3; if two players choose C, then each C-chooser gets 2 and the D-chooser gets 4; if one player chooses C, then the C-chooser gets 1 and each D-chooser gets 3; and if no player chooses C, then each D-chooser gets 2. See also sure-thing principle. NPD abbrev.