Beliefs about Radiation Stigma and Support for Fukushima

Last registered on March 19, 2025
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Pre-Trial

Trial Information

General Information

Title
Beliefs about Radiation Stigma and Support for Fukushima
RCT ID
AEARCTR-0015563
Initial registration date
March 14, 2025

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
March 19, 2025, 8:57 AM EDT

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

Locations

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Primary Investigator

Name
Hidetoki Nakayama
Affiliation
Graduate School of Economics, Osaka university
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Other Primary Investigator(s)

Additional Trial Information

Status
In development
Start date
2025-03-14
End date
2027-03-31
Keywords
Behavior, Environment & Energy, Lab
Additional Keywords
Dictator Game, Radiation, Discrimination, Public Economics, Behavioral Economics, Online laboratory experiment
JEL code(s)
C91, D63
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
More than 10 years have passed since the nuclear accident caused by the Great East Japan Earthquake in March 2011. Scientific evidence shows that there is a low possibility of radiation-induced health problems. However, radiation stigma still exists, and this can lead to discrimination.
This study examines radiation stigma and whether providing information that mitigates stigma can influence beliefs and behavior. Through nationwide online experiments with financial incentives, we investigate whether participants’ beliefs about the extent of societal stigma adjust in response to the intervention. Furthermore, we examine whether changes in beliefs translate into donating behavior.
External Link(s)

Registration Citation

Citation
Nakayama, Hidetoki. 2025. "Beliefs about Radiation Stigma and Support for Fukushima." AEA RCT Registry. March 19. https://doi.org/10.1257/rct.15563-1.0
Sponsors & Partners
Experimental Details

Interventions

Intervention(s)
The study employs a randomized controlled trial (RCT) with two groups: Control group & Treatment group.
Intervention Start Date
2025-03-14
Intervention End Date
2025-03-21

Primary Outcomes

Primary Outcomes (end points)
1. Perceived social norms regarding radiation risks (incentivized).
2. Amount of donation.
Primary Outcomes (explanation)
* Please see the analysis plan for how to create these indicators.

Secondary Outcomes

Secondary Outcomes (end points)
1. Trust in various information sources in related contexts (food safety and environmental contamination).
2. Participant's own belief about radiation risks.
3. Amount of donation in the previous year.
We ask these outcomes before the experiment tasks.
Secondary Outcomes (explanation)
* Please see the analysis plan for how to create these indicators.

Experimental Design

Experimental Design
This study employs a randomized controlled trial (RCT) to examine whether providing information about radiation risks affects discriminatory behavior and belief updating. Participants are randomly assigned to either a control or treatment group.

Participants engage in two incentivized tasks: a belief elicitation task to assess perceived social stigmas and a experiment to measure donation behavior for Fukushima disaster recovery fund. Only the treatment group receives the intervention message before answering the second round of these tasks.
Experimental Design Details
Not available
Randomization Method
Participants are randomly assigned to either the control or treatment group by an online survey company using computer-generated randomization. Stratification is conducted based on gender, age, and region to ensure balanced allocation across treatment arms.
Randomization Unit
Individuals
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
Not applicable (individual-level randomization).
Sample size: planned number of observations
4,000 participants.
Sample size (or number of clusters) by treatment arms
2,000 participants in the control group and 2,000 participants in the treatment group.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Based on the results from a previous experiment (https://www.socialscienceregistry.org/trials/11419), the expected Cohen’s d is 0.06. Assuming equal variance, a significance level of 0.05, and a power of 0.8, the required sample size per group is approximately 2,000 participants.
Supporting Documents and Materials
IRB

Institutional Review Boards (IRBs)

IRB Name
Graduate School of Economics, The University of Osaka IRB
IRB Approval Date
2025-02-27
IRB Approval Number
R70217-2-2
Analysis Plan

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