A Dictator Game Experiment with the COVID-19 Vaccinated and Unvaccinated People

Last registered on March 21, 2022
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Pre-Trial

Trial Information

General Information

Title
A Dictator Game Experiment with the COVID-19 Vaccinated and Unvaccinated People
RCT ID
AEARCTR-0008951
Initial registration date
February 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
February 08, 2022, 9:46 AM EST

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

Last updated
March 21, 2022, 2:23 AM EDT

Last updated is the most recent time when changes to the trial's registration were published.

Locations

Country
Japan
Region

Primary Investigator

Name
Shusaku Sasaki
Affiliation
Osaka University
Contact Primary Investigator

Other Primary Investigator(s)

PI Name
Hirofumi Kurokawa
PI Affiliation
University of Hyogo
Contact Investigator

Additional Trial Information

Status
On going
Start date
2022-01-28
End date
2025-03-31
Keywords
Behavior, Governance, Health, Other
Additional Keywords
COVID-19, Vaccination behavior, Vaccinated people, Unvaccinated people, Dictator game, Ingroup bias, Outgroup bias, Ingroup favoritism, Cooperation, Discrimination, Altruism, Reciprocity, Public economics, Health economics, Behavioral economics, Online laboratory experiment, Japan
JEL code(s)
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
In this study, we conduct a dictator game experiment with the COVID-19 vaccinated and unvaccinated people in Japan, and ascertain allocation tendencies between two anonymous individuals, between two vaccinated individuals or two unvaccinated individuals, and between a vaccinated individual and an unvaccinated individual. By so doing, we assess “ingroup bias,” “outgroup bias,” and “ingroup-favoritism” of vaccinated and unvaccinated people, respectively. Here, ingroup bias is defined as the difference between the money amounts allocated to an individual of the same group as the allocator and to an anonymous individual in the dictator game experiment. Outgroup bias is defined as the difference between the money amounts allocated to an individual of a different group from the allocator’s and to an anonymous one, and ingroup-favoritism is defined as the difference between the money amounts allocated to an individual of the same group and to an individual of the different group.

Specifically, we employ an experimental design that allows for both between- and within-individual comparisons to conduct the following analyses. First, in the between-analysis, we test the existence of ingroup bias, outgroup bias, and ingroup-favoritism in each group of vaccinated and unvaccinated individuals. In addition, we examine how these biases differ between vaccinated and unvaccinated individuals. We further investigate how the biases change between when the vaccination status of the allocator is not informed to the recipient and when it is informed to them.

Next, in the within-analysis, we test whether individuals' ingroup bias, outgroups bias, and ingroup favoritism are associated with their real-world attitudes and behaviors. In both the vaccinated and unvaccinated group, we examine the association between their biases and attitudes toward the COVID-19-related policies. In the vaccinated group, we also examine the association between their biases and the timing of COVID-19 vaccination.

To stably manage a society under a pandemic, it is crucial to build cooperative relationships between vaccinated and unvaccinated people. This study can contribute to the smooth construction of such cooperative relationships.
External Link(s)

Registration Citation

Citation
Sasaki, Shusaku and Hirofumi Kurokawa. 2022. "A Dictator Game Experiment with the COVID-19 Vaccinated and Unvaccinated People." AEA RCT Registry. March 21. https://doi.org/10.1257/rct.8951-3.1
Sponsors & Partners
Experimental Details

Interventions

Intervention(s)
We set the following treatment conditions in the dictator game experiment:

- Private-Ingroup: An allocator is informed that a recipient belongs to the ingroup (a vaccinated individual in the vaccinated sample, or an unvaccinated individual in the unvaccinated sample). The allocator is anonymous for the recipient.
- Private-Outgroup: An allocator is informed that a recipient belongs to the outgroup (an unvaccinated individual in the vaccinated sample, or a vaccinated individual in the unvaccinated sample). The allocator is anonymous for the recipient.
- Public-Ingroup: An allocator is informed that a recipient belongs to the ingroup. The recipient is notified of the vaccination status of the allocator.
- Public-Outgroup: An allocator is informed that a recipient belongs to the outgroup. The recipient is notified of the vaccination status of the allocator.
Intervention Start Date
2022-02-10
Intervention End Date
2022-02-28

Primary Outcomes

Primary Outcomes (end points)
Allocation in the dictator game experiment
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
- Attitudes toward the COVID-19-related policies (Balancing infectious disease control and socio-economic activities, vaccination certification and negative test results, and financial incentives for encouraging vaccination)
- Dates of the first and second COVID-19 vaccination uptakes (Vaccinated sample, only)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
We conduct dictator game experiments in the following five conditions:

(I) Anonymous: A recipient is anonymous for an allocator. The allocator is also anonymous for the recipient.
(II) Private-Ingroup: An allocator is informed that a recipient belongs to the ingroup (a vaccinated individual in the vaccinated sample, or an unvaccinated individual in the unvaccinated sample). The allocator is anonymous for the recipient.
(III) Private-Outgroup: An allocator is informed that a recipient belongs to the outgroup (an unvaccinated individual in the vaccinated sample, or a vaccinated individual in the unvaccinated sample). The allocator is anonymous for the recipient.
(IV) Public-Ingroup: An allocator is informed that a recipient belongs to the ingroup. The recipient is notified of the vaccination status of the allocator.
(V) Public-Outgroup: An allocator is informed that a recipient belongs to the outgroup. The recipient is notified of the vaccination status of the allocator.

One subject participates in five dictator game experiments as an allocator. We randomly set the order of the above conditions to create eight groups in the vaccinated and unvaccinated samples, respectively. After we first present the dictator game in the Anonymous condition (I) in all the eight groups, we randomly set the order of the Private (II, III) and Public (IV, V) conditions. Then, within each of the Private and Public conditions, we randomly set the order of the ingroup conditions (II, IV) and outgroup conditions (III, V). Consequently, each of the vaccinated and unvaccinated samples have eight groups.

Furthermore, to address potential order effects caused by successive participation in the dictator games in the within-analysis, we create a control group where we present the anonymous dictator game (I) five times. Totally, each of the vaccinated and unvaccinated samples have nine groups, including the control group.

We explain more details in the attachment of the analysis plan.
Experimental Design Details
Not available
Randomization Method
Stratified randomization by a survey company. The strata are based on age, gender, and baseline generosity.
Randomization Unit
Individuals
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
N/A
Sample size: planned number of observations
1,600 individuals (800 vaccinated individuals and 800 unvaccinated individuals)
Sample size (or number of clusters) by treatment arms
800 vaccinated individuals include eight treatment groups (8*80 vaccinated individuals=640 vaccinated individuals) and one control group (160 vaccinated individuals). Similarly, 800 unvaccinated individuals include eight treatment groups (8*80 unvaccinated individuals=640 unvaccinated individuals) and one control group (160 unvaccinated individuals).

In the between-analysis, we combine two or more treatment groups to create a paired group. Therefore, the sample size of one paired group is more than 160.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
In the meta-analysis (Balliet et al., 2014), d of the ingroup-favoritism is 0.32. When we calculate the necessary sample size under the condition of power=0.8 and alpha=0.05, it becomes 155 for each group. Reference: Balliet, D., Wu, J., & De Dreu, C. K. (2014). Ingroup favoritism in cooperation: a meta-analysis. Psychological bulletin, 140(6), 1556.
Supporting Documents and Materials
IRB

Institutional Review Boards (IRBs)

IRB Name
Center for Infectious Disease Education and Research, Osaka University IRB
IRB Approval Date
2022-01-14
IRB Approval Number
N/A
Analysis Plan

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