TY - JOUR
T1 - Ingroup favoritism and intergroup cooperation under indirect reciprocity based on group reputation
AU - Masuda, Naoki
N1 - Funding Information:
I thank Mitsuhiro Nakamura and Hisashi Ohtsuki for valuable discussions and acknowledge the support provided through Grants-in-Aid for Scientific Research (Nos. 20760258 and 23681033 , and Innovative Areas “ Systems Molecular Ethology ” (No. 20115009 )) from MEXT, Japan.
PY - 2012/10/21
Y1 - 2012/10/21
N2 - Indirect reciprocity in which players cooperate with unacquainted other players having good reputations is a mechanism for cooperation in relatively large populations subjected to social dilemma situations. When the population has group structure, as is often found in social networks, players in experiments are considered to show behavior that deviates from existing theoretical models of indirect reciprocity. First, players often show ingroup favoritism (i.e., cooperation only within the group) rather than full cooperation (i.e., cooperation within and across groups), even though the latter is Pareto efficient. Second, in general, humans approximate outgroup members' personal characteristics, presumably including the reputation used for indirect reciprocity, by a single value attached to the group. Humans use such a stereotypic approximation, a phenomenon known as outgroup homogeneity in social psychology. I propose a model of indirect reciprocity in populations with group structure to examine the possibility of ingroup favoritism and full cooperation. In accordance with outgroup homogeneity, I assume that players approximate outgroup members' personal reputations by a single reputation value attached to the group. I show that ingroup favoritism and full cooperation are stable under different social norms (i.e., rules for assigning reputations) such that they do not coexist in a single model. If players are forced to consistently use the same social norm for assessing different types of interactions (i.e., ingroup versus outgroup interactions), only full cooperation survives. The discovered mechanism is distinct from any form of group selection. The results also suggest potential methods for reducing ingroup bias to shift the equilibrium from ingroup favoritism to full cooperation.
AB - Indirect reciprocity in which players cooperate with unacquainted other players having good reputations is a mechanism for cooperation in relatively large populations subjected to social dilemma situations. When the population has group structure, as is often found in social networks, players in experiments are considered to show behavior that deviates from existing theoretical models of indirect reciprocity. First, players often show ingroup favoritism (i.e., cooperation only within the group) rather than full cooperation (i.e., cooperation within and across groups), even though the latter is Pareto efficient. Second, in general, humans approximate outgroup members' personal characteristics, presumably including the reputation used for indirect reciprocity, by a single value attached to the group. Humans use such a stereotypic approximation, a phenomenon known as outgroup homogeneity in social psychology. I propose a model of indirect reciprocity in populations with group structure to examine the possibility of ingroup favoritism and full cooperation. In accordance with outgroup homogeneity, I assume that players approximate outgroup members' personal reputations by a single reputation value attached to the group. I show that ingroup favoritism and full cooperation are stable under different social norms (i.e., rules for assigning reputations) such that they do not coexist in a single model. If players are forced to consistently use the same social norm for assessing different types of interactions (i.e., ingroup versus outgroup interactions), only full cooperation survives. The discovered mechanism is distinct from any form of group selection. The results also suggest potential methods for reducing ingroup bias to shift the equilibrium from ingroup favoritism to full cooperation.
KW - Community
KW - Cooperation
KW - Indirect reciprocity
KW - Outgroup homogeneity
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U2 - 10.1016/j.jtbi.2012.07.002
DO - 10.1016/j.jtbi.2012.07.002
M3 - Article
C2 - 22796271
AN - SCOPUS:84864408643
VL - 311
SP - 8
EP - 18
JO - Journal of Theoretical Biology
JF - Journal of Theoretical Biology
SN - 0022-5193
ER -