PDG: Prisoners Dilemma Game


Social psychological test for cooperation or competition

In this interactive test the subject plays with an imaginary other person (in fact the computer), and in 10 “rounds” he always chooses to work together (choice A) or work against him (choice B, for his own gain). The other reacts according to certain strategies. Profits and losses are determined by a (to be set up) payoff matrix. There are a maximum of 4 different games (tasks or conditions) to choose from, to choose from five different strategies:

A: Tit for Tat: the other player cooperates the first round (A), then imitates the previous choice of the subject

B: Suspicious Tit for Tat: the other player counterworks (choice B) in the 1st round, then always imitates the previous choice of the subject

C: Hardball: the other player always opposes (choice B), except on round 5 and 10

D: Change of Heart: the first 5 rounds are counterworked by the other player (B), then cooperates (A)

E: Win-Stay, Lose-Change (Pavlov-strategy): the other player starts with cooperation (A), but after that it only cooperates if the subject and the computer both make the same choice.

The order of the games can be randomized. Because the instruction is fairly complex, it can be set that six multiple choice questions are asked about the payoff matrix prior to the games. Only when an (adjustable) percentage has been achieved correctly the subject can begin. Choices can be made with the mouse (or with the finger on the touch screen).

The individual performances on the different conditions can be compared with standards of male (N = 245) or female (N = 919) psychology students.


  • Axelrod, R. The Evolution of Cooperation(Basic Books, New York, 1984).
  • Nowak,M. & Sigmund,K. (1993). A strategy of win-stay, lose-shift that outperforms tit-for-tat in the Prisoner’s Dilemma game. Nature, 364, 56-58.