Cooperation and Altruism in One-Shot Prisoners' Dilemma Games

Reputation and Increased Cooperation in Repeated Prisoners' Dilemma Games

Interpreting Experimental Game Results

An economist designs a study where two anonymous participants, who will only interact once, must independently choose one of two actions: 'Action A' or 'Action B'. The outcomes are set up so that choosing 'Action B' always yields a higher personal payoff for an individual, regardless of the other participant's choice. However, if both participants choose 'Action A', they each receive a better payoff than if they both choose 'Action B'. What is the primary research question this experimental design is best suited to investigate?

Theoretical Predictions vs. Experimental Observations

An economist conducts a study where participants play a game with a partner. In the game, each player can choose to either 'cooperate' or 'not cooperate'. The payoffs are structured such that not cooperating always yields a higher individual reward for that round, regardless of the partner's choice, but mutual cooperation leads to a better outcome for both than mutual non-cooperation. The study compares two conditions:

• Condition 1: Participants play the game only once with an anonymous partner.
• Condition 2: Participants play the game for ten consecutive rounds with the same partner.

The results show that the rate of cooperation is significantly higher in Condition 2 than in Condition 1. Which of the following is the most robust explanation for this finding?

Critiquing an Experimental Design

Designing an Experiment to Test a Hypothesis

An economist studies a game where two individuals can either 'cooperate' or 'defect'. Defecting always yields a higher personal payoff for that round, but mutual cooperation is better for both than mutual defection. Match each experimental condition below with the primary factor that would explain a player's decision to cooperate in that scenario.

An economist observes that in a one-time, anonymous interaction where two participants can choose to either 'cooperate' or 'defect', a certain percentage of participants choose to 'cooperate'. If the experiment is modified so that participants are first shown a brief, neutral video of their anonymous partner, economic theory predicts this change will decrease the rate of cooperation.

Predicting Experimental Outcomes in a Cooperation Game

An economist conducts an experiment where pairs of anonymous participants play a game one time. In this game, each player can choose to either 'cooperate' or 'defect'. Defecting always provides a higher individual payoff for that round, but if both players cooperate, they achieve a better outcome than if they both defect. The experiment has three conditions:

• Condition 1 (Control): Participants are given no information about their partner. The cooperation rate is 25%.
• Condition 2 (In-Group): Participants are told their partner is a student from their own university. The cooperation rate is 40%.
• Condition 3 (Out-Group): Participants are told their partner is a student from a rival university. The cooperation rate is 10%.

Based on these results, what is the most precise conclusion an economist can draw?

An economist conducts a study where participants play a game with a partner. In the game, each player can choose to either 'cooperate' or 'not cooperate'. The payoffs are structured such that not cooperating always yields a higher individual reward for that round, regardless of the partner's choice, but mutual cooperation leads to a better outcome for both than mutual non-cooperation. The study compares two conditions:

• Condition 1: Participants play the game only once with an anonymous partner.
• Condition 2: Participants play the game for ten consecutive rounds with the same partner.

The results show that the rate of cooperation is significantly higher in Condition 2 than in Condition 1. Which of the following is the most robust explanation for this finding?

Theoretical Predictions vs. Experimental Observations