​1.    Recruitment of Human Subjects

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University undergraduates will be invited to take the online survey by emailing an invitation to the undergraduate listserve. The email text is found in the document, Appendix_Survey_Instrument.docx. The target sample size is n=60. Willing participants click on a link in the invitation email, upon which they are routed to a Qualtrics-based survey. They are informed that only the first 60 to volunteer will be able to take the online survey. Recruitment ends when the target number of participants have completed the online survey (termination of the survey is done through Qualtrics).

 

The online information sheet provides standard information, approved by the university IRB, and includes a click-on tab to allow potential participants to provide formal consent to take the survey.

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2    Online Survey

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The online survey is implemented via the Qualtrics platform. The introductory part of the survey introduces the project and principal investigator (PI), provides assurances of anonymity/confidentiality, information about foreseeable risks and benefits of the research, voluntary nature of the survey, and contact information for the PI. At the end of this section, the respondent will be asked to click on a box signifying their written consent to continue with the survey. The survey continues only if the box is clicked.

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The groups will be asked to divide up the nominal monetary amount (180) between themselves and the recipient, which will be described as a local environmental conservation project. The actual amounts donated to the conservation project will be subsequently given to the project, and the amounts kept by the survey participant will be given to the participant, at the end of the project. To minimize the effects of personal knowledge of particular projects, the description will be kept general (i.e., no other particulars will be given). The question, given to both groups, is as shown below:

“In this part of the exercise, you will be asked to divide up a sum of money, 180 in total, between yourself and an environmental conservation project. The project, run by a nonprofit involves such activities as tree planting and restoration, ecological habitat protection, and soil conservation. In the space provided below, fill in the amount you would assign to yourself and the amount you would donate to the environmental conservation initiative. About 5-10 days after you complete the survey, we will contact you by email and provide you with instructions on how to collect the amount you assigned to yourself. The amount will be provided in the form of supermarket coupons.”

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Participants will also be informed that, when they subsequently receive the amounts they decided to keep for themselves, that the amount in the envelope will not be known by the project assistant handing them the envelope (the amounts were put in the envelope by a different project staff member). This is to minimize the effect of social pressure or judgement on the subject’s decision to donate.

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A follow-up question asks the respondent to reconsider their donation if there is a matching grant that doubles the amount paid to the beneficiary (while the respondent’s allocation to self remains the same). 

The follow-up question is as follows:

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"The following is an opportunity to increase the donation with a matching fund. You are still going to divide up HKD180 as before, but this time, the project will match your donation to the conservation program (that is, double the amount you give to the program). How much of the HKD180 would you like to donate to the conservation program if there is a matching grant? (Note: The amount entered has to be an integer between 0 and 180. Otherwise, the number cannot be entered.) You can choose to change your original donation (either decreasing or increasing it), or you can choose to specify the same donation as before –either way, the program will match the donation and double the actual money received by the conservation program."

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A follow-up email is sent to all participants informing them of where to go to pick up an envelope containing the amounts they chose to keep. They are also informed that the amount they donated, plus matching, will be donated to the environmental conservation project. More information is provided at this point on the ecological conservation project and the NGO managing it. 

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The  final amounts chosen were paid out (the amount kept paid to the subject and the amount donated, with matching, paid to the NGO). Note that, when amounts kept by the subject fell in between what the supermarket coupons could be summed up to (as the coupons were in round increments), cash was used to top up the amount to exactly that specified by the participant. 
 

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3    Data Analysis

After all the survey respondents have completed the survey, the data will be downloaded from Qualtrics. The resulting data is grouped into three categories: responses that (i) increased, (ii) maintained, or (iii) decreased, the original donation. For the purposes of the illustrative exercise, we assume that each group corresponds to a distinct mode of other-regard and choose three different functional forms to fit to each group. Parameters for each of the three functions were solved for using maximum likelihood estimation (details of the estimation procedure are to be found in the file,
maximum_likelihood_calculations_august_2026.docx). The corresponding functional forms used are: (i) Tradeoff, (ii) Cobb-Douglas, and (iii) Maximin functions. 

 

The functions are shown below: 
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4    Confidentiality and Quality Control Practices

 

​​The only identifier provided by the respondent is his/her email address. To maintain confidentiality and anonymity, a subject ID number will be assigned each respondent, and the data file will consist of the subject ID number and the data, but no email addresses. A separate subject ID file will be created matching subject ID numbers and email addresses. Only the PI will have access to the subject ID file and will keep this file in his personal laptop and a project-dedicated USB drive. One year after completion of the project, the subject ID file will be deleted. The file will be password protected.

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The data file will be kept in the hard drive of the PI’s personal laptop and a dedicated USB drive. The file will be password protected.

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​5        Ethics Approval

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The research protocol was approved by the university Human and Artefacts Research Ethics Committee (Protocol ID: HREP-2024-0249). Survey respondents provided written informed consent.

6     General Survey 

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The matching game is a stand-alone exercise that was included as part of a larger survey of determinants of pro-social decision-making. The larger survey included collection of demographic data as well as other control variables. These other data parameters did not affect the relevant data of the matching game and were part of a separate, independent investigation. The matching game is a stand-alone component that is independent of the larger survey. The protocol/questionnaire for the larger survey is provided in the file, Appendix_Survey_Instrument.docx.