by Lucius Caviola and Joshua D. Greene
Science Advance | 18 Jan 2023 | Vol 9, Issue 3
Materials and Methods
(excerpt)
All reported main studies, including the final proof of concept, were preregistered, except for study 7 (which was a pretest for the proof of concept). For more detailed descriptions of the methods and results, please refer to the Supplementary Materials available at https://osf.io/zu6j8/. In all studies (apart from the proof of concept), the sample size was determined before data collection. Across studies 1 to 7, we recruited participants using Amazon Mechanical Turk (MTurk). All participants were taken from different samples. The financial stakes in studies 1 to 7 were probabilistically implemented (executed by lottery), enabling the use of higher stakes (27–29). As per our preregistrations, participants in studies 1 to 7 were excluded for either failing the attention check or (where applicable) for indicating that they did not believe that the financial stakes were real. All key results held when no participants were excluded (see the Supplementary Materials). Unless otherwise specified, all conducted t tests were two-sided. Our studies, including the proof-of-concept demonstration, were approved by Harvard’s Committee on the Use of Human Subjects, and for all studies, informed consent was obtained.
Study 1
We recruited 1039 U.S. American participants online via MTurk. They received $0.47 in payment for their participation. A total of 144 participants were excluded for either failing the attention check or for indicating that they did not believe that the financial stakes were real, leaving a final sample of 895 (432 females and 463 males, Mage = 40.5 and SDage = 12.84). This study was preregistered at https://aspredicted.org/ks3ez.pdf.
There were five conditions: (i) the favorite-only baseline condition in which participants simply had the option to donate to their favorite charity; (ii) the control condition in which participants could donate exclusively to their favorite charity (all-favorite) or exclusively to the expert-recommended highly effective charity (all-effective); (iii) the three-option bundle condition, which included the option to make a 50/50 bundle donation (favorite-effective) along with the all-favorite and all-effective options; (iv) the two-option bundle condition, which included the 50/50 favorite-effective option and the all-favorite option; and (v) the free-split bundle condition, which included the all-favorite option, the all-effective option, and a favorite-effective option in which participants can freely choose the allocation proportion.
First, participants identified their favorite charity by entering its name and website URL. In all conditions apart from the favorite-only condition, participants were presented with a short and accurate description of one of the world’s most effective charities: Evidence Action’s Deworm the World Initiative (see the Supplementary Materials). Participants were also informed that this charity is, according to experts, approximately 100 times more effective than typical charities (see http://GiveWell.org).
Next, it was explained to participants that they will be given the option to donate up to $100 to charity and that, at the end of the study, we will randomly select one participant and execute their decision. Participants were then presented with the donation allocation options, which varied by condition. For example, in the three-option bundle condition, they were presented with three options: donate all to the effective charity, split 50/50, and donate all to their favorite charity. In the favorite-only condition, participants skipped this part.
On the next page, participants chose a donation amount ($0 to $100) to be allocated in the proportion previously specified. Critically, participants had the option to keep the money for themselves. It was explained that any amount not donated will be allocated to the participant in the form of an Amazon voucher, should they be the randomly chosen participant. Thus, this task has real stakes for the donor and not just for the charities. After responding to some exploratory questions (see the Supplementary Materials), they responded to an attention check question, a question about whether they believed that the financial stakes were real, and to a set of demographic questions.
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