Identity fusion is a relatively unexplored form of alignment with groups that entails a visceral feeling of oneness with the group. This feeling is associated with unusually porous, highly permeable borders between the personal and social self. These porous borders encourage people to channel their personal agency into group behavior, raising the possibility that the personal and social self will combine synergistically to motivate pro-group behavior. Furthermore, the strong personal as well as social identities possessed by highly fused persons cause them to recognize other group members not merely as members of the group but also as unique individuals, prompting the development of strong relational as well as collective ties within the group. In local fusion, people develop relational ties to members of relatively small groups (e.g., families or work teams) with whom they have personal relationships. In extended fusion, people project relational ties onto relatively large collectives composed of many individuals with whom they may have no personal relationships. The research literature indicates that measures of fusion are exceptionally strong predictors of extreme pro-group behavior. Moreover, fusion effects are amplified by augmenting individual agency, either directly (by increasing physiological arousal) or indirectly (by activating personal or social identities). The effects of fusion on pro-group actions are mediated by perceptions of arousal and invulnerability. Possible causes of identity fusion--ranging from relatively distal, evolutionary, and cultural influences to more proximal, contextual influences--are discussed. Finally, implications and future directions are considered.

Is it good to cooperate? Testing the theory of morality-as-cooperation in 60 societies." Current Anthropology 60(1).

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Willingness to lay down one’s life for a group of non-kin, well documented historically and ethnographically, represents an evolutionary puzzle. Building on research in social psychology, we develop a mathematical model showing how conditioning cooperation on previous shared experience can allow individually costly pro-group behavior to evolve. The model generates a series of predictions that we then test empirically in a range of special sample populations (including military veterans, college fraternity/sorority members, football fans, martial arts practitioners, and twins). Our empirical results show that sharing painful experiences produces “identity fusion” – a visceral sense of oneness – which in turn can motivate self-sacrifice, including willingness to fight and die for the group. Practically, our account of how shared dysphoric experiences produce identity fusion helps us better understand such pressing social issues as suicide terrorism, holy wars, sectarian violence, gang-related violence, and other forms of intergroup conflict.

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What motivates ordinary civilians to sacrifice their lives for revolutionary causes? We surveyed 179 Libyan revolutionaries during the 2011 conflict in Libya. These civilians-turned-fighters rejected Gaddafi's jamahiriyya (state of the masses) and formed highly cohesive fighting units typical of intense conflicts. Fighters reported high levels of "identity fusion"-visceral, family-like bonds between fighters and their battalions. Fusion of revolutionaries with their local battalions and their own families were extremely high, especially relative to Libyans who favored the revolution but did not join battalions. Additionally, frontline combatants were as strongly bonded to their battalion as they were to their own families, but battalion members who provided logistical support were more fused with their families than battalions. Together, these findings help illuminate the social bonds that seem to motivate combatants to risk their lives for the group during wartime.uring the revolutionary war in Libya in 2011, thousands of civilians formed small revolutionary battalions to overthrow the Gaddafi-led regime. Although most fighters were not kin, in such conflicts cocombatants characteristically express feelings of brotherhood for each other (1). In some cases, these feelings are strong enough to compel them to sacrifice their lives for one another. Such willingness to self-sacrifice for genetic strangers has puzzled scientists since Darwin. By embedding ourselves in a battalion during the revolution, we were able to explore this phenomenon empirically.Participants were either frontline combatants (high exposure to risk and suffering) or logistical supporters (lower exposure) who completed a brief questionnaire. Items were inspired by recent evidence suggesting that some members of groups develop a visceral, family-like sense of unity or "identity fusion" with their group (2, 3). Evidence suggests that fusion with a group (e.g., one's country) is a key proximal cause of personally costly, progroup behavior or "parochial altruism." For instance, fused individuals are particularly apt to say they will fight and die for their country (4, 5). In hypothetical scenarios based on the classic "trolley dilemma," fused persons endorse diving in front of a speeding train to save the lives of fellow group members (5-7). These findings suggest that identity fusion may predispose civilians to enact extreme sacrifices in naturally occurring settings, such as joining a militia that is pursuing a goal that is shared by one's group.In July 2011, 4 months into the Libyan revolution, the second author (B.M.) joined a humanitarian relief convoy traveling from Malta to Misrata. There, he noted that rebels spontaneously formed microgroups of three to five fighters constituting each battalion. Rebels were together constantly, eating, praying, sleeping, and fighting as "bands of brothers" or katiba. As the revolution came to an end, the first author (H.W.) joined B.M. and met with the revolutionary leadership in Misrata. The leaders agreed ...

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SignificanceDo human societies from around the world exhibit similarities in the way that they are structured and show commonalities in the ways that they have evolved? To address these long-standing questions, we constructed a database of historical and archaeological information from 30 regions around the world over the last 10,000 years. Our analyses revealed that characteristics, such as social scale, economy, features of governance, and information systems, show strong evolutionary relationships with each other and that complexity of a society across different world regions can be meaningfully measured using a single principal component of variation. Our findings highlight the power of the sciences and humanities working together to rigorously test hypotheses about general rules that may have shaped human history.