Implementation Details ---------------------- This page describes how our lab implemented the procedures required by the official protocol for the RRR. It also describes and justifies any additions to or departures from that protocol. You can view the official protocl and the main project page for this RRR using these links: - Official Protocol: [https://osf.io/ypd78/][1] - Main RRR project page: [https://osf.io/scu2f/][2] ---------- #### Experimenters #### Fernando Ferreira-Santos (PhD), Assistant Professor at the University of Porto, Faculty of Psychology and Education Sciences. Experience in behavioral, electrophysiological, and neuroimaging research in economic decision-making. Tiago O. Paiva (MSc), PhD Student at the University of Porto, Faculty of Medicine. Experience in behavioral and electrophysiological research in economic decision-making. Eva C. Martins (PhD), Assistant Professor at the Maia University Institute - ISMAI. Experience in the translation and validation of psychological instruments as well as in behavioral research. Carlos Mauro (PhD), Assistant Professor at the Catholic University of Portugal, Faculty of Economics and Management. Experience in behavioral economics. Fernando Barbosa (PhD), Assistant Professor at the University of Porto, Faculty of Psychology and Education Sciences. Experience in behavioral, electrophysiological, and neuroimaging research in economic decision-making. ---------- #### Setting/Lab/Equipment #### The study will take place in a dedicated computer room, illustrated in the figure below. The room contains 12 computer workstations running Windows and with Internet acess ensuring that participants can be tested in groups of 12 people. The room arrangement is such that computer screens cannot be easily observed by other participants or experimenters (large boards between rows, desktop cases within rows). ![Testing Environment][3] ---------- #### Sample, subjects, and randomization #### **Target sample size:** We will schedule a total of 16 sessions with 12 participants in each session, for a target sample of 192 participants. **Target sample demographics:** The researchers involved in the study are affiliated with three university institutions in the Porto metropolitan area (Portugal), and the study participants will be undergraduate students recruited from those institutions. First year psychology students will be recruited, but students from other disciplines will be included. An appropriate age (18-35) will be a requirement for inclusion in the study. The proportion of female participants will be checked when data is collected for 80% of the sample. At that time, we will calculate the breakdown between genders to ensure we stay within the protocol interval (e.g., in an extreme case were we would have 80% females, only males would be recruited from there on). **Minimum sample size after exclusions:** 150 participants (75 per condition). **Stopping rule(s):** If, after completing all of the scheduled testing sessions and after any exclusions, we have fewer than 75 participants in either condition, we will schedule additional sessions of 12 participants until we have usable data from at least 75 participants in each condition. **Randomization to conditions:** Participants will be randomly assigned to conditions by the provided Qualtrics Script. **Blinding to conditions:** Each participant will only be able to read from her own computer screen given the physical setup of the computer room where testing will be conducted. **Exclusion rules:** We will use the exclusion rules defined in the official protocol. Exclusion decisions will be made by someone blind to condition assignment. **Procedures for handling testing sessions for which the number of participants is not a multiple of 4:** To ensure that all places are filled, we will overbook sessions by two participants, and redirect them to other studies in our lab if needed. Given that our room only has 12 computers, in the event of having less than 12 participants show up, we will test eight and invite the remaining to another study. ---------- #### Software/Code #### We will be using a Portuguese translation of the Qualtrics scripts provided and have succesfully tested them in our lab. ---------- #### Differences from the official protocol #### **Currency changes:** Our participants will receive a show-up fee of €2.5 and an endowment of €2. The scale where participants decide how much to contribute to the common pool will display markers in increments of €0.40 from €0.00 to €2.00. These values take into account the euro-dollar exchange rate and the fact that local purchasing power in Portugal is about 55% of that of the United States of America (Numbeo). **Translation to Portuguese:** The only changes made to the experimental materials was to translate them to Portuguese and to adapt one question. We do not have a subject pool and indeed these are not usual in Portugal, so we modified the item to allow participants to report that they are not part of any subject pool. All members of our team have experience in the sytematic translation of research materials and are proficient in academic English. The translation process was the following: 1. [Translation from English to Portuguese][4] (TOP) 2. [Back-translation by researcher naive to the original English version][5] (FFS) 3. Blind comparison of original English and back-translated English versions (ECM) 4. [Discussion and modifications for final version][6] (all) **Minor change not anticipated at pre-registration**: Before the beginning of the session, one of the researchers entered the computer ID into the Qualtrics survey (because all computers share one external Internet IP making it impossible to identify individual entries in Qualtrics); participants did not see this question. [1]: https://osf.io/ypd78/ [2]: https://osf.io/scu2f/ [3]: https://dl.dropboxusercontent.com/u/8555497/RRR-Rand%282012%29/Testing%20Environment.png [4]: https://osf.io/5fgz8/ [5]: https://osf.io/tfcv7/ [6]: https://osf.io/srkyx/