Experimental Design
We introduce a spatial public good game with overlapping neighborhoods. Six subjects interact and are located on a circle. Subjects are identified with their respective location (i ∈ {A,B,C,D,E,F}. For each subject, we define a neighborhood Ni. We consider closed and overlapping neighborhoods. The former serves as a baseline and forms a variant of a typical three-player public good game, NA = NB = NC = {A,B,C} and ND = NE = NF = {D,E, F}. In the latter, the neighborhood of a player is given by her location and her two direct neighbors. That is, NA = {A,B, F}, NB = {A,B,C}, NC = {B,C,D}, . . . ,NF = {E, F,A}. Here, each experimental subject benefits from public good investments in his location as well as the location of her two neighbors. Conversely, investments in any location benefit three players.
The experimental treatments vary the endowments the individual players receive. We compare homogenous endowments of all players with heterogenous settings where three players receive a large, and three players receive a small endowment. In such heterogenous settings, the spatial distribution matters: we compare clustered endowment settings where three direct neighbors are rich (A, B,C) while the other three are poos (D,E,F) and alternating endowment settings where rich and poor alternate (A, C, E rich; B,D,F poor). We consider this experimental setting as both novel and empirically relevant.
Our experiment consists of five treatments. As a baseline, we reconsider “closed” neighborhood settings where groups of three individuals play a standard public good game. The only variant to the typical public good setup is the simultaneous presence (and information about) another group as well as the option to invest in any location. In this closed neighborhood setting, we consider a homogeneous income treatment, CNhom, where all agents have an endowment of 30, and a heterogenous setting, CNhet, where in one group two players are endowed with 20 and one player with 40, while in the other group two players are endowed with 40 and one player with 20 tokens. The other treatments introduce the overlapping neighborhoods as described above. Again, we consider homogenous endowments, ONhom, and two heterogenous settings, ONhetCL and ONhetAL, in which endowments are clustered or alternate, respectively. We otherwise stick to a linear public good setting. That is, each player can invest in any location. The payoff from investments to a player then is proportional to the total sum of investments in her neighborhood.
The experimental sessions are scheduled to begin by the end of January 2023. They will be conducted by the experimental laboratory of the University of Hamburg (Germany) in an in-person lab setting. The University of Hamburg does not issue IRBs but instead they have an internal ethical approval process in which a 'Declaration of compliance with Terms of Use and Ethical Standards' (DoC) needs to be signed and submitted. The details of the experiment are hereby approved by the dean of the faculty. The DoC has been submitted and approval has been received.