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The Courtesy Game: Efficiency and Inequality

Last registered on September 08, 2022


Trial Information

General Information

The Courtesy Game: Efficiency and Inequality
Initial registration date
September 08, 2022

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
September 08, 2022, 12:38 PM EDT

First published corresponds to when the trial was first made public on the Registry after being reviewed.



Primary Investigator

Helmut-Schmidt-University, Hamburg

Other Primary Investigator(s)

PI Affiliation
Hamburg University of Technology
PI Affiliation
Hamburg University of Technology
PI Affiliation
Helmut-Schmidt-University, Hamburg

Additional Trial Information

In development
Start date
End date
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Using a laboratory experiment, we aim to study a new game, the courtesy game. The courtesy game is a simultaneous two-player game in which each player must choose between two strategies, X and Y. Game parameters are designed such that both players’ weakly dominant strategy is X, and the strategy profile (X, X) is a Nash equilibrium. Moreover, there are two other asymmetric Nash equilibria (X, Y) and (Y, X), that are Pareto efficient to the symmetric Nash equilibrium, and yielding the X-player the higher payoff. Thus, the Y-player is the courteous player, who accepts a lower payoff than her opponent in order to achieve efficiency. However, choosing Y is accompanied with a courtesy dilemma, since the strategy profile (Y, Y) yields the worst outcome for both players. In different variations of the game (one shot, repeated) we test if players play the weakly dominant strategy X or the courteous strategy Y.
External Link(s)

Registration Citation

Heinrich, Timo et al. 2022. "The Courtesy Game: Efficiency and Inequality." AEA RCT Registry. September 08.
Experimental Details


The aim of the experiment is to test for our new game, the courtesy game, if participants play the weakly dominant strategy of the game. We designed a simultaneous, two players, two strategies basic version of the game. We run two treatments:

• Repeated: Participants play 10 rounds of the game in groups of two under a perfect stranger matching with feedback after each round.
• One shot: Participants play one round of the game in groups of two under with direct feedback.
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
We are interested in:

i) the strategy choice of players.
ii) beliefs of players about the opponents’ strategy choice in each round.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
We are interested in:

i) the major motive (payoff maximization, altruism, inequality aversion, efficiency or envy) behind the strategy choice – derived from questions in the post-experimental questionnaire.
ii) the correlation between the strategy choice and personal characteristics like risk attitude, courtesy and patience – we derive these characteristics by self-reported measures from the post-experimental questionnaire.
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
The laboratory experiment will be programmed in oTree (Chen et al. 2016) and conducted with participants of the University of Hamburg. Participants will read the instructions on screen and are requested to answer control questions before proceeding with the experiment.

Participants play 10 rounds (1 round in treatment one shot) of the game under a complete stranger matching in groups of two. Participants are informed of the matching procedure in the instructions. In each round, participants have to decide between strategy X or Y. After each round, participants receive feedback.

Before each round, participants are asked to state their belief what strategy choice (X or Y) the other player in this round will make. This belief request is unincentivised.

In the post-experimental questionnaire, we ask participants for:

• gender, age, field of study,
• risk, courtesy and patience attitudes,
• motives (payoff maximization, altruism, inequality aversion, efficiency or envy) behind their decisions in the experiment.

Further design details:

• Complete Stranger Matching
• On an individual level, the display of strategies in the payoff matrix (XY or YX) is randomized between subjects.
• Feedback after each round: Own strategy choice, strategy choice of the other player, own payoff for the respective round, payoff of the other player for the respective round
• Feedback at the end of the experiment: Own accumulated payoff
Experimental Design Details
Parametrization of the payoff matrix:

X, X: 10, 10
X, Y: 20, 10
Y, X: 10, 20
Y, Y: 0, 0
Randomization Method
Randomization (perfect stranger matching and randomization of strategies within the payoff matrix) is done by a computer program (oTree).
Randomization Unit
Individual level (randomization of strategies within the payoff matrix).
Experimental session level (perfect stranger matching).
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
2 sessions à 24 participants for the repeated game (one treatment).
1 session à 24 participants for the one shot game (one treatment).
Sample size: planned number of observations
2 sessions x 24 participants x 10 rounds = 480 individual observations for the repeated game, respectively 240 group observations (one group = 2 participants). 1 session x 24 participants x 1 round = 24 individual observations for the one shot game, respectively 12 group observations (one group = 2 participants).
Sample size (or number of clusters) by treatment arms
48 participants in 2 sessions for the repeated game (one treatment).
24 participants in 1 session for the one shot game (one treatment).
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
German Association for Experimental Economic Research e.V.
IRB Approval Date
IRB Approval Number


Post Trial Information

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Is the intervention completed?
Data Collection Complete
Data Publication

Data Publication

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Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials