Milestones and Endogenous Feedback Mechanisms in Promoting Cooperation in Dynamic VCM.

Last registered on April 16, 2024


Trial Information

General Information

Milestones and Endogenous Feedback Mechanisms in Promoting Cooperation in Dynamic VCM.
Initial registration date
April 15, 2024

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
April 16, 2024, 3:50 PM EDT

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


There is information in this trial unavailable to the public. Use the button below to request access.

Request Information

Primary Investigator

University of Exeter

Other Primary Investigator(s)

PI Affiliation
University of Melbourne
PI Affiliation
University of Melbourne

Additional Trial Information

In development
Start date
End date
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
This research uses insights from behavioral economics to study the role of feedback formation in reducing the free-riding problem in team settings. We examine whether letting team members choose their preferred feedback mechanisms promotes higher or lower team contributions than exogenously assigning a feedback mechanism to the team. Participating in the dynamic voluntary contribution mechanism (VCM) game, team members choose between receiving feedback about their team’s progress on a regular basis (time-based feedback) or based on the achievement of intermediate milestones (milestone-based feedback). The findings from this study will contribute to the growing literature on feedback mechanisms as well as have policy implications for designing feedback in team contexts.
External Link(s)

Registration Citation

Erkal, Nisvan, Boon Han Koh and Nguyen Lam. 2024. "Milestones and Endogenous Feedback Mechanisms in Promoting Cooperation in Dynamic VCM.." AEA RCT Registry. April 16.
Experimental Details


Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
1) Proportion of participants choosing each type of feedback mechanism.
2) Total team contributions.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
1) Individual contributions by team members.
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
The main task of this study is the dynamic voluntary contribution mechanism (VCM) game. Participants take part in the dynamic VCM game in teams of three. At the start of the game, every team member receives an endowment of 30 effort units which they can use to contribute to the joint project over the six contribution rounds. Contributions that have been made to the joint project cannot be reversed. The payoff is realized at the end of the sixth round. For each effort unit contributed to the joint project, every member receives 0.4 tokens (marginal per capita return = 0.4), while for each effort unit a member has remaining, he or she receives 1 token.

Team members will vote for a feedback mechanism that they want to use in their team. The feedback mechanism can be either time-based or milestone-based. With time-based feedback (T), team members are given information after each round about the total team contributions to the joint project so far. Meanwhile, with milestone-based feedback (M), team members are informed after each round whether the total team contributions have exceeded pre-determined milestones of 15, 30, 45, 60, 75, or 90 effort units.
Experimental Design Details
Not available
Randomization Method
Randomization is done at the session level. Participants are randomly assigned to one of three treatments before the sessions are run, and they do not know the pre-determined treatment assignment. The order of introducing feedback mechanisms (in the endogenous treatment) is also randomly determined before each session.
Randomization Unit
The unit of randomization is at the experimental session level.
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
45 groups for each exogenous treatment and 90 groups for endogenous treatment.
Sample size: planned number of observations
540 participants
Sample size (or number of clusters) by treatment arms
135 participants for each exogenous treatment and 270 participants for the endogenous treatment.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Using data from the prior study by Erkal, Koh & Lam (2023), the effect size between exogenous milestone and exogenous time-based feedback mechanisms is around 1.2 standard deviation. We expect that the contributions with endogenous feedback will be between two exogenous feedback mechanisms, so the expected effect size is around 0.6 standard deviations, assuming the standard deviations are the same between treatments. The main unit of observation in our analysis is at the group level. With the medium effect size of 0.6 standard deviations, Type I error of 0.05, and statistical power of 0.8, the power calculation requires 45 observations (groups) for each treatment (Exo-T, Exo-M, as well as each mechanism under the Endo treatment) or equivalently 135 participants per treatment. Assuming that an equal proportion of groups vote to implement each mechanism, we will collect data up to about 270 participants (about 90 groups) for the endogenous treatment.

Institutional Review Boards (IRBs)

IRB Name
Business and Economics & Melbourne Business School Human Ethics Advisory Group (University of Melbourne)
IRB Approval Date
IRB Approval Number
Analysis Plan

There is information in this trial unavailable to the public. Use the button below to request access.

Request Information