Do the Number of Appropriators from the Commons Matter in Controlled Laboratory Environments?

Many controlled laboratory experiments have shown non-binding communication among appropriators from a common pool to be an effective way to reduce over-appropriation from the commons. The controlled laboratory environments have tended to be environments with fewer than 10 participants. Recent work by Buckley et al. (2017) found that non-binding communication is not successful in reducing appropriation effort in a controlled laboratory environment with 12 participants. A conjecture was that there might be a difference between 12 participants and 8 participants (the typical number used by Ostrom et al. 1994 in their seminal work and used in many subsequent studies by others). This paper presents an environment that utilizes the CPR setting identical to that used by Buckley et al. (2017) reduces the number of appropriators from 12 to 8. Eight sessions (4 with and 4 without non-binding communication) are run using the Buckley et al. (2017) environment with 8 participants. The results suggest that the number of participants may not be an important factor in driving the differences between the impact that non-binding communication has on the Buckley et al. (2017) and Ostrom et al. (1994) environments. Alternate conjectures are presented to account for the differences.