Online Beauty Contest Game

Last registered on February 18, 2019


Trial Information

General Information

Online Beauty Contest Game
Initial registration date
February 18, 2019

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
February 18, 2019, 9:17 PM EST

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



Primary Investigator

University of Copenhagen

Other Primary Investigator(s)

Additional Trial Information

Start date
End date
Secondary IDs
We examine the process of reasoning among subjects playing variants of the iterated beauty contest game on Amazon Mechanical Turk. Our findings are substantially different from the behaviors observed in laboratory and newspaper experiments reported in the literature. In general, we do not find any strong evidence in favor of higher-order reasoning in the first round as well as in the following iterations of the game, which puts into question the presence of any strategic thinking among the vast majority of subjects. In addition, our results suggest that players are only weakly responsive to competitive as well as to cooperative incentives.
External Link(s)

Registration Citation

Engelhardt, Robin. 2019. "Online Beauty Contest Game ." AEA RCT Registry. February 18.
Former Citation
Engelhardt, Robin. 2019. "Online Beauty Contest Game ." AEA RCT Registry. February 18.
Sponsors & Partners

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Experimental Details


Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
- the effect of group size, incentives and nudging on the process of reasoning in an experimental iterated beauty contest game among players recruited from Amazon Mechanical Turk.
- the presence of higher-order reasoning and
- the effects of competitive and cooperative incentives.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
Workers on Amazon Mechanical Turk accept our HIT (human intelligence task), provide informed consent, and wait until there are enough workers who have accepted the HIT to form random groups (grouped by arrival) of size 2, 4 or 8, respectively, depending on the treatment condition. When a group has been formed, instructions are displayed for 90 seconds. After pressing NEXT, turkers see a page where they have to enter into a form field an integer number between 0 and 100. When all turkers in a group have done so, a result page is displayed, where they can see their own guess, the guesses of the other players, the average and the 2/3 of the average as well as information about whether they have won a bonus in the current found and what their total payoff is for the time being. After this, the previous steps are repeated for a total of 8 rounds. Every time turkers enter a new number, they can see a list of the 2/3 of the average of the previous rounds. Turkers have 90 seconds to think about a number. After eight rounds, turkers are required to give feedback by answering the question: What strategy did you use while playing this game?, after which they are thanked for their participation.
Experimental Design Details
Software: otree 1.8
Randomization Method
Randomization of group formation by arrival time.
Randomization Unit
Four treatments: 1: split, 2: low, 3: high, 4: control. Each treatment has randomized groups of 2, 4 or 8 players, respectively.
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
1 platform: AMT
Sample size: planned number of observations
1454 workers on AMT
Sample size (or number of clusters) by treatment arms
86 groups control-treatment, 104 groups split-treatment, 106 groups low-treatment, 107 groups high-treatment.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
Research Ethics Committee, Faculty of Humanities, University of Copenhagen
IRB Approval Date
IRB Approval Number


Post Trial Information

Study Withdrawal

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Is the intervention completed?
Data Collection Complete
Data Publication

Data Publication

Is public data available?

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials