How a norm-nudge affects group decisions in a social dilemma experiment
Last registered on March 09, 2020


Trial Information
General Information
How a norm-nudge affects group decisions in a social dilemma experiment
Initial registration date
March 08, 2020
Last updated
March 09, 2020 7:47 PM EDT
Primary Investigator
Heidelberg University
Other Primary Investigator(s)
Additional Trial Information
In development
Start date
End date
Secondary IDs
Research that leverages social norms to induce desirable behaviour has generally studied norm-based interventions when decisions are made by individuals. However, in reality decisions are often made by groups. This is particular true for natural resource use in developing countries.
With our experiment, we aim to build a bridge between the lab and the field to inform policy makers whether a norm-nudge could improve resource management at Lake Victoria, Tanzania.
We study the effect of norm-nudges by varying whether participants are given social information about past behavior of other groups.
Groups in our experiment are recruited from fishing crews.
At Lake Victoria, there are two relevant forms of decision making on board.
Decisions are either made by all crew members together (majority) or by a captain (representative).
Thus, we study the effect of a norm-nudge both when group action is determined by majority, or by a randomly selected representative.
External Link(s)
Registration Citation
Diekert, Florian. 2020. "How a norm-nudge affects group decisions in a social dilemma experiment." AEA RCT Registry. March 09.
Experimental Details
Intervention Start Date
Intervention End Date
Primary Outcomes
Primary Outcomes (end points)
Average cooperation by teams in a repeated two-team prisoner's dilemma experiment. Binary choice set.
Primary Outcomes (explanation)
Secondary Outcomes
Secondary Outcomes (end points)
Secondary Outcomes (explanation)
Experimental Design
Experimental Design
The experiment is a repeated two-team prisoner's dilemma game with disapproval. The prisoner's dilemma is played with a binary choice set, framed as a decision to take points from a collective account or to leave points in a collective account. Three participants play together in a team. Two teams form a collective and share an account with eight points. Both teams can either take four points from the collective account (defect) or leave the points in the collective account (cooperate). Moves are made simultaneously. The remaining points increase and are then distributed equally. For four points left in the collective account, both teams receive three points, i.e. a marginal per agent return of 0.75.
Our treatment variation crosses an empirical norm nudge with two forms of group decision making processes. We first vary whether participants are given social information about past behaviour of other groups. Second, we impose that group decisions are either determined by a majority or by a randomly chosen representative.
Experimental Design Details
Randomization Method
By design
Randomization Unit
Experimental sessions
Was the treatment clustered?
Experiment Characteristics
Sample size: planned number of clusters
36 experimental sessions
Sample size: planned number of observations
336 groups decisions
Sample size (or number of clusters) by treatment arms
13 sessions in majority treatment with social information
13 sessions in majority treatment without social information
5 sessions in representative treatment with social information
5 sessions in representative treatment without social information
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
IRB Name
German Association for Experimental Economic Research e.V.
IRB Approval Date
IRB Approval Number
Analysis Plan
Analysis Plan Documents
Changing Collective Action Study Plan

MD5: bf7748bb55c8f2da0c08b57ac75837cd

SHA1: 0e995f349e3d26e4b0b28f57f6c78e2a570b85e4

Uploaded At: March 08, 2020

Post Trial Information
Study Withdrawal
Is the intervention completed?
Is data collection complete?
Data Publication
Data Publication
Is public data available?
Program Files
Program Files
Reports, Papers & Other Materials
Relevant Paper(s)