Bauer et al on war and cooperation
A 2016 review of about 20 studies finding that individual exposure to war violence tends to raise local cooperation, mostly toward the in-group.
Refs: Kemp on conflict and in-group cooperation Churchill on war as the human default Cultural evolution Cooperation at scale
Summary
Michal Bauer, Christopher Blattman, Julie Chytilová, Joseph Henrich, Edward Miguel and Tamar Mitts review nearly 20 observational studies, from many countries, of how exposure to war violence affects cooperation. They re-analyze the 16 with comparable, publicly available data. The average effect on a summary index of cooperation (behavior in experimental games, community participation, trust and similar measures) is positive, statistically significant and moderate in size.
The common expectation was that violence erodes social capital, and the data reject it. The effect is not a recovery effect: it shows up in anonymous games, in children, and years after the fighting ends. Aid that raised incomes in post-war Sierra Leone did not produce the same rise in cooperation.
Where the authors can tell, the increase is largely parochial. Several lab studies find more prosocial behavior toward the in-group and none toward out-groups. They flag this as preliminary and as the main open question. It cuts both ways: war may help intragroup cooperation and post-conflict reconstruction while raising the risk of later division and renewed conflict.
The authors also report that similar patterns appear after crime, post-election violence, earthquakes and tsunamis, which suggests the mechanism is a response to survival threats in general rather than to war specifically. They say the evidence does not yet decide between competing explanations (changed social preferences, adherence to local norms, changed beliefs, trauma and post-traumatic growth), though it weighs against a purely economic or belief-based account.
Excerpts
Most of the papers in this emerging literature do agree on one central matter: that the data strongly reject the common view that communities and people exposed to war violence will inevitably be deprived of social capital, collective action, and trust.
This evidence for parochial altruism, while preliminary, matters because war might enhance intragroup cooperation and facilitate post-conflict reconstruction while simultaneously raising the risk of future social divisions and renewed intergroup conflict.
— Michal Bauer, Christopher Blattman, Julie Chytilová, Joseph Henrich, Edward Miguel and Tamar Mitts, "Can War Foster Cooperation?", Journal of Economic Perspectives 30, no. 3 (2016): 249–74, pp. 270–72 (doi:10.1257/jep.30.3.249)
Excerpts checked against the text of the NBER working paper version (NBER Working Paper 22312, June 2016, "Conclusion" section), not the journal pagination.
So what
The finding qualifies the picture in Churchill on war as the human default: if war is common, so is a mechanism that builds cooperation within groups under threat. It fits the group-competition accounts in Cultural evolution, which the authors cite (Bowles, Turchin, Henrich). The cooperation it produces is mostly in-group, so its value for cooperation across larger groups depends on how widely the in-group is drawn. The authors note that a civil war between ethnic groups could strengthen co-ethnic ties while corroding cross-group ones, whereas an external aggressor could bond a whole nation.
