· Recruitment and admission
Participants were recruited via email in Tomsk and via the recruiting systems BeLab-System in Moscow and hroot (Bock et al., 2014) in Kiel and Bonn. Upon arrival, we checked that only students having a German (Russian) passport could take part in the session. Participants were given an information sheet and were asked to sign an informed consent form prior to entering the laboratory. Participants were randomly assigned to an experimental treatment (see Table 1) without knowing about the decision tasks nor other treatments. In all four cities, we followed the same experimental procedure documented in a detailed English script (see Supplementary Files: Experimenter Script). Upon arrival, participants were randomly allocated to individual cubicles divided by opaque separators (Fig. 2) to ensure privacy of decisions. They were randomly divided into groups of six with three group members each being from two different locations in Germany and/or Russia depending on the treatment.
All sessions were computerized using the experimental software z-Tree (Fischbacher, 2015; See Supplementary Files: Ztree File 1/2/3/4 for Ztree programmes). Participants from the two locations interacted via Internet and took their decisions at the same time. They received equivalent experimental instructions in their respective native language. Participants were informed that all participants would take their decisions simultaneously and would be provided with equivalent instructions. (See the English translation of the instructions in Supplementary Files: Instructions).
Participants were given ample time to read the instructions and ask clarifying questions which were answered in private. To ensure that participants understood the decision task and the procedure of the experiment, we summarized the instructions in a PowerPoint© presentation with text in German or Russian (See Supplementary Files: Powerpoint presentation of instruction summary / Powerpoint presentation of of decisions stages and information feedback for the English translation of the powerpoint presentations). We also made clear that due to our confidential payment method we were not able to trace any individual participant’s decisions. Participants then had to answer a set of comprehension questions on their computer screens – showing German text in the German locations and Russian text in the Russian locations also in international treatments. The decision stage did not start unless all participants had answered all control questions correctly.
Before entering the decision part of the experiment, participants were presented an information recap in PowerPoint© to make them familiar with the information options provided throughout the experiment.
· Videoconference link
To attenuate possible suspicions on the existence of the other lab, we set up two Skype© connections during the session, lasting a few minutes each. Lead researchers would briefly greet each other and introduce the other participants on a large projector screen visible to all participants. Participants were not allowed to talk or communicate with each other in this phase. To show that the interaction was occurring in real time, we followed (Eckel and Wilson, 2006) and asked some participants in one location to state some numbers. Such numbers were communicated via internet to researchers at the other location, who then wrote these numbers on a slip of paper and showed them on the projector screen through the videoconference link. The same procedure was repeated at the other location. An identical protocol was repeated in all sessions, with the exception that researchers communicated in the respective national languages in the National treatments, interacted in English in the International Open treatments, while the Skype© link was muted in the International Blind treatments. We believed that this set of procedures was the best suited to fully assure participants that they were not being deceived and that all the information given in the instruction was truthful.
After the videoconference link, participants completed a practice period on their computers. In order not to bias actual experimental decisions, participants were not communicated others’ decisions in the practice period but rather were only given the opportunity to get familiar with the commands of the software. Afterwards, the experimenters in both locations explained how the lottery would be implemented. Finally, participants made their decisions in periods 1 to 10 in No-Sanctions (NS)- or Sanction (S)-treatments.
To illustrate the participants' decision task, Fig. 3 provides the decision screen for the contribution decision in Stage 1. In addition to making their decisions, each member was informed about the contributions of all six group members as well as about the tokens in each of their personal accounts, both accumulated over the previous periods. Furthermore, they saw the total number of tokens contributed to the project and the current probability that the loss event will not occur.
After participants had taken their decisions they could get visual information on each group member’s contributions in each of the previous periods (Fig. 4). In NS-treatments, the period ended at this point and each participant was informed about their contribution in the current period as well as about everyone’s personal account in tokens at the end of the previous and the current periods.
In S-treatments, participants entered Stage 2 and made their decision on how many tokens they wanted to spend to sanction each of the other group members. Before having done so they could retrieve information on each group member’s contributions in each of the previous periods (Fig. 4) and in the current period (Fig. 5), the accumulated number of tokens in each group member’s personal account, and the number of tokens each group member spent in the last period on each of the other group members to reduce that person’s personal account.
At the end of Stage 2 of each period, participants got the same information as in NS-treatments and learned the number of tokens spent on others and deducted from their own account.
· Final procedures
Having finished the experimental tasks, the lottery to decide whether the loss event would occur was played out. From a bag containing lottery chips numbered 1 - 100, one chip was drawn by a participant. If the number was larger than the percentage x of the target amount the group members had contributed to the group project, the loss event occurred and 75% of the amount collected in each group member’s personal account was lost. If the number drawn was smaller or equal to x, the loss event did not occur and each group member was paid out the total amount in his or her personal account. This procedure was repeated for each of the four groups participating in a session. The outcomes of the lottery draws were transmitted via Skype© to both participating labs but information on the lottery outcome relevant for a specific group was not made available to the participants until they had filled in a non-incentivized questionnaire on social characteristics, risk attitudes (Falk et al., 2018), personal values (Schwartz, 1992) and other questions taken from the World Value Survey (see Supplementary Files: Questionnaire). The survey questions were available and externally validated in both languages.
Finally, we applied an anonymized payment procedure by distributing the payments from the experiment plus the show-up fee and receipts in an envelope marked with the cubicle number. Participants took the money, signed the receipt, confidentially put the receipt into a box, and left the laboratory. All features of the experimental design and procedure were common knowledge and apparently did not raise any questions. Sessions lasted about 2 hours on average. Mean earnings were 25.00€ in Germany and 750 Ruble in Russia (12.5€ at the time of running the experiment) including the show-up fee.