The Impact of Default on Charitable Giving: An Online Experiment in Japan

We will conduct an experiment using the economic experiment platform oTree to measure the impact of default on charitable giving. In the experiment, we will intervene by using a screen where participants decide what points to donate to an NGO engaged in environmental conservation activities. We will randomly assign participants to three groups.

We will conduct an experiment using the economic experiment platform oTree to measure the impact of default on charitable giving. In the experiment, we will intervene by using a screen where participants decide what points to donate to an NGO engaged in environmental conservation activities. We will randomly assign participants to three groups.
- Control Group: Participants in this group will see a screen for deciding donation points, with the input field initially blank.
- Low Default Group: Participants in this group will see a screen for deciding donation points, with 10 points pre-entered in the input field.
- High Default Group: Participants in this group will see a screen for deciding donation points, with 40 points pre-entered in the input field.
In all groups, participants can choose to donate between 0 and 50 points. If they enter a number outside this range, a warning will appear, and they will not be able to proceed to the next screen. If participants do not want to donate, they must enter 0 points into the input field, as leaving the input field blank will prevent advancing to the next screen.

2025-03-12

2025-03-13

1. Whether to donate
2. Unconditional Average Donation Amount

1. Whether or not to donate at least one point.
2. The average donation amount, including those who did not donate

1. Conditional Average Donation Amount
2. Total Donation Amount
3. Whether the Donation Amount Matches the Default Value
4. Expected Average Donation Amount by Other participants
5. Expected Donation Amount Desired by the Charity

1. The average donation amount among those who donated at least one point
2. The total sum of donations collected in each group
3. Whether the donation amount matches the default Value
4. Estimated average points donated by Other participants
5. The amount guessed as what the charity hoped participants would donate

1. Experimental Setup
This study aims to examine the impact of default on charitable giving in Japan using a donation experiment in the format of a dictator game. The experiment is conducted on oTree, an economic experiment platform. Participants are residents of Japan aged 18 or older and are recruited through Yahoo! Crowdsourcing, a Japanese crowdsourcing service. Participants receive two types of compensation: a fixed reward and a performance-based reward. A fixed reward is guaranteed for all participants upon participation in the experiment and completion of the questionnaire, while the performance-based reward is determined by their performance in the donation experiment. The maximum amount for the performance-based reward is 50 JPY. The compensation is provided in the form of points usable through PayPay, a Japanese payment service, instead of cash.

2. Procedure
The experiment will proceed as follows:

1. Obtain Informed Consent
2. Pre-experiment Questionnaire
3. Experiment Instructions & Comprehension Test
4. Donation Experiment
A donation experiment in the format of a dictator game will be conducted. Participants are initially given 50 points and instructed to enter how much they wish to donate to an environmental conservation organization operating in Japan.
5. Post-experiment Questionnaire
6. Compensation Payment

Additionally, to identify participants who may answer the questionnaire without closely reading the instructions, the Directed Questions Scale (DQS) will be included twice in the pre-experiment questionnaires. A warning will be displayed only if the first DQS answer is incorrect. If the second DQS answer is incorrect, the participant will not receive a warning, and they will be excluded from the analysis.

3. Intervention
We will conduct an experiment using the economic experiment platform oTree to measure the impact of default on charitable giving. In the experiment, we will intervene by using a screen where participants decide what points to donate to an NGO engaged in environmental conservation activities. We will randomly assign participants to three groups.

4. Hypotheses
This section will be disclosed after the experiment.

5. Analysis
This section will be disclosed after the experiment.

1. Experimental Setup
This study aims to examine the impact of default on charitable giving in Japan using a donation experiment in the format of a dictator game. The experiment is conducted on oTree, an economic experiment platform. Participants are residents of Japan aged 18 or older and are recruited through Yahoo! Crowdsourcing, a Japanese crowdsourcing service. Participants receive two types of compensation: a fixed reward and a performance-based reward. A fixed reward is guaranteed for all participants upon participation in the experiment and completion of the questionnaire, while the performance-based reward is determined by their performance in the donation experiment. The maximum amount for the performance-based reward is 50 JPY. The compensation is provided in the form of points usable through PayPay, a Japanese payment service, instead of cash.

2. Procedure
The experiment will proceed as follows:

1. Obtain Informed Consent
2. Pre-experiment Questionnaire
・Socioeconomic demographics: Age, Gender, etc.
・Environmental Awareness
・Impression for Charitable Organizations
・Past Donation Experience
・Awareness and Donation Experience with Target Organizations
・General Trust
・Cognitive Reflection Test (CRT)
・Conformity Scale

3. Experiment Instructions & Comprehension Test
Participants will receive an explanation about the donation experiment and the target organizations they can donate to. After the instructions, we will give a five-question comprehension test about the experiment. If a participant answers even one question incorrectly, they will be redirected back to the instruction screen and will not proceed to the donation experiment. If they fail the comprehension test three times consecutively, their participation will end at that point, and only a fixed compensation will be provided.

4. Donation Experiment
A donation experiment in the format of a dictator game will be conducted. Participants are initially given 50 points and instructed to enter how much they wish to donate to an environmental conservation organization operating in Japan.

5. Post-experiment Questionnaire
・Simple questions regarding understanding of the experiment
・Norms regarding donation amounts
・Evaluation of the default

6. Compensation Payment

Additionally, to identify participants who may answer the questionnaire without closely reading the instructions, the DQS will be included twice in the pre-experiment questionnaires. A warning will be displayed only if the first DQS answer is incorrect. If the second DQS answers is incorrect, the participant will not receive a warning, and they will be excluded from the analysis.

3. Intervention
We will conduct an experiment using the economic experiment platform oTree to measure the impact of default on charitable giving. In the experiment, we will intervene by using a screen where participants decide what points to donate to an NGO engaged in environmental conservation activities. We will randomly assign participants to three groups.
- Control Group: Participants in this group will see a screen for deciding donation points, with the input field initially blank.
- Low Default Group: Participants in this group will see a screen for deciding donation points, with 10 points pre-entered in the input field.
- High Default Group: Participants in this group will see a screen for deciding donation points, with 40 points pre-entered in the input field.
In all groups, participants can choose to donate between 0 and 50 points. If they enter a number outside this range, a warning will appear, and they will not be able to proceed to the next screen. If participants do not want to donate, they must enter 0 points into the input field, as leaving the input field blank will prevent advancing to the next screen.

4. Hypotheses
This study aims to analyze the impact of defaults on charitable giving in Japan and to test the following hypotheses:

H1: Compared to other experimental groups, the donation rate will increase in the low default group.
H2: Compared to other groups, the unconditional average donation amount will increase in the high default group.

In addition to testing these hypotheses, we plan to conduct exploratory analyses using pre- and post-experiment questionnaires. Specifically, we aim to elucidate the mechanisms by which default influences charitable giving and investigate the heterogeneity of effects. Furthermore, we will utilize machine learning methods to estimate the CATE and validate an optimal policy for maximizing the effects of default.
The details are documented in the attached file "Theoretical Background", which elaborates on the theoretical foundation of these hypotheses.　

5. Analysis
In this study, we will conduct analyses using statistical hypothesis testing and generalized linear models, including Ordinary Least Squares (OLS). We will employ statistical hypothesis testing to validate the proposed hypotheses and complement this with regression analysis.

1) Statistical Hypothesis Testing
We will perform tests for differences in population proportions regarding donation rates (whether to donate) and the use of default values. For an unconditional average donation amount, a conditional average donation amount, and a total donation amount, we will use tests for differences in population means. Based on these results, we will assess the validity of the hypotheses. We will apply Holm's method to adjust for multiple comparisons in these tests.

2) Regression Analysis
To account for potential imbalances in covariates between groups, we will conduct regression analysis to support the test results. OLS will serve as the baseline method. For binary outcomes (e.g., whether to donate), we will use logistic or probit regression. For outcomes that are discrete or continuous (e.g., an unconditional average donation amount), we will employ regression techniques suitable for the outcome distribution, such as the Tobit model. Additionally, regression analysis will be used to explore mechanisms and analyze heterogeneity of the effect.
Furthermore, as part of our exploratory analysis, we plan to estimate the CATE using machine learning methods to validate optimal policies. Specifically, we anticipate using the Generalized Random Forest.
The details are documented in the attached file "Pre-Analysis Plan,"

Randomization is done by oTree

Individual

No

N/A

2,000 individuals

Approximately 666 participants will be included in each group

Based on the results of Study 2c by Goswami and Urminsky (2016), we calculated the effect sizes for donation rates and average donation amounts, yielding Cohen’s h = 0.28 and Cohen’s d = 0.22, respectively. These effect sizes compare scenarios with and without default settings. Due to the absence of prior studies with calculable effect sizes specifically comparing different default values, we proceed assuming similar effect sizes. For simplicity, we set both Cohen’s h and Cohen’s d at 0.25 for this study. The significance levelαis set at 0.05, and the power is set at 0.80. The main outcomes of this study are the donation rate and the unconditional average donation amount, with the experimental groups divided into three. To test the hypothesis, comparisons across all groups for the two outcomes are necessary, leading to a total of six tests. The Holm correction is applied for multiple testing adjustments in the experiment, while the Bonferroni correction, a more stringent criterion, is used in the sample size design. Based on these conditions, the calculated sample size required per group is approximately 390. Considering potential exclusions due to inadequate responses and the need for heterogeneity analysis, we set the overall sample size goal for the experiment at 2,000 participants. Reference： Goswami, I., & Urminsky, O. (2016). When should the Ask be a Nudge? The Effect of Default Amounts on Charitable Donations. Journal of Marketing Research, 53(5), 829–846. https://doi.org/10.1509/jmr.15.0001