Optimization Incentives, Learning, and Strategy Selection in Indefinitely Repeated Prisoner's Dilemmas

Last registered on June 22, 2026
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Pre-Trial

Trial Information

General Information

Title
Optimization Incentives, Learning, and Strategy Selection in Indefinitely Repeated Prisoner's Dilemmas
RCT ID
AEARCTR-0018810
Initial registration date
June 11, 2026

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
June 22, 2026, 6:34 AM EDT

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

Locations

Country
Germany
Region

Primary Investigator

Name
Maximilian Andres
Affiliation
Universität Bremen
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Other Primary Investigator(s)

PI Name
Yongping Bao
PI Affiliation
Universität Bremen
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PI Name
Yves Breitmoser
PI Affiliation
Universität Bielefeld
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PI Name
Sebastian Fehrler
PI Affiliation
Universität Bremen
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PI Name
Juri Moritz Nithammer
PI Affiliation
Universität Potsdam
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Additional Trial Information

Status
In development
Start date
2026-06-15
End date
2026-07-31
Keywords
Behavior
Additional Keywords
infinitely repeated prisoner's dilemma, optimization premium, learning, strategy choice, cooperation
JEL code(s)
C72, C73, D81, D83
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
This pre-analysis plan describes an experimental design on cooperation in indefinitely repeated Prisoner's Dilemmas. The design varies optimization incentives while holding fixed the normalized strategic environment and the payoff kernel within treatment cores, and the normalized strategic environment. Its objective is to separate two central margins that are often confounded in repeated-game data: the normalized strategic environment and the cardinal payoff cost of choosing a suboptimal strategy.
External Link(s)

Registration Citation

Citation
Andres, Maximilian et al. 2026. "Optimization Incentives, Learning, and Strategy Selection in Indefinitely Repeated Prisoner's Dilemmas." AEA RCT Registry. June 22. https://doi.org/10.1257/rct.18810-1.0
Sponsors & Partners
Experimental Details

Interventions

Intervention(s)
This is a laboratory experiment on cooperation in indefinitely repeated Prisoner's Dilemmas. The design employs a 2×2 between-subject factorial structure that independently varies (i) the cardinal optimization-incentive level and (ii) the normalized strategic environment. The optimization-incentive level is either High (Treatment-Condition) or Low (Control-Condition), and the normalized strategic environment is either risk-dominant or not risk-dominant.
Intervention (Hidden)
Intervention Start Date
2026-06-15
Intervention End Date
2026-07-31

Primary Outcomes

Primary Outcomes (end points)
Round-1 Cooperation.
Primary Outcomes (explanation)
Binary indicator equal to 1 if the subject cooperated in the first round of a supergame.

Secondary Outcomes

Secondary Outcomes (end points)
Strategy Choices, Continuation-play cooperation, and convergence speed.
Secondary Outcomes (explanation)
Complete plan of actions in round-1 and in each of the four memory states (cc, cd, dc, dd).

Experimental Design

Experimental Design
Each participant plays multiple infinitely repeated supergames.

Within each supergame, participants choose between two actions in each round. After each round, the supergame continues with a probability implemented as a random draw at the end of each round. If the draw terminates the supergame, a new supergame begins.

After each round, subjects observe the outcome of that round: their own action, their co-player's action, and both payoffs.
Experimental Design Details
Randomization Method
Random subsets of the subject pool are invited to sessions via e-mail and, within each session, participants are randomly assigned to computer terminals---and thus to matching groups---through public shuffling of a deck of cards with numbers. Treatments for each session are initially assigned through two coin flips (one for each treatment dimension) but for later sessions, we will need to assign the treatments where we still need to collect observations (see below).
Randomization Unit
Individuals in matching groups.
Was the treatment clustered?
Yes

Experiment Characteristics

Sample size: planned number of clusters
32 matching groups (8 per treatment).
Sample size: planned number of observations
>= 256 participants (>= 8 participants per matching group).
Sample size (or number of clusters) by treatment arms
32 matching groups (8 per treatment).
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
See details in the pre analysis plan (pdf).
Supporting Documents and Materials
IRB

Institutional Review Boards (IRBs)

IRB Name
German Association for Experimental Economic Research e.V
IRB Approval Date
2026-06-08
IRB Approval Number
aPfR59CN
Analysis Plan

Analysis Plan Documents

Optimization Incentives and Cooperation Pre-Analysis Plan

MD5: eb9f3115097935d6a8f20f4dd8a0003f

SHA1: 1f94c7fb494794df572786b0d24bf2c74ec833c7

Uploaded At: June 10, 2026

Post-Trial

Post Trial Information

Study Withdrawal

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Intervention

Is the intervention completed?
No
Data Collection Complete
Data Publication

Data Publication

Is public data available?
No

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials