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The legacy of war on social and political behaviour

The past decade has seen rapid growth in an interdisciplinary body of research examining the legacy of war on social and political behaviour. This column presents a meta-analysis and synthesis of this research. Evidence from surveys and experiments from over 40 countries reveals a stylised fact: individual exposure to war-related violence tends to increase social cooperation, community participation, and pro-social behaviour. However, these changes are mainly directed towards people from the same community.

Nearly half of all nations in the world have experienced some form of external or internal armed conflict in the past half century. Many international development researchers and policymakers describe war as “development in reverse” (Collier et al. 2003), having persistent adverse effects on all factors relevant for development – physical, human, and social capital. Yet a long history of scholarship from diverse disciplines offers a different perspective on the legacies of war. Historians and anthropologists have noted how, in some instances, war fostered societal transitions from chiefdoms to states and further strengthened existing states (Carneiro 1970, Flannery and Marcus 2003, Tilly 1985, Choi and Bowles 2007, Morris 2014, Diamond 1999). Meanwhile, both economists and evolutionary biologists have also argued that war has spurred the emergence of more complex forms of social organisation, potentially by altering people’s psychology (Bowles 2008, Turchin 2015).

Until recently, a paucity of individual-level data from conflict and post-conflict societies prevented researchers from systematically exploring the legacies of war on social and political behaviour. In the last decade, however, interdisciplinary teams of researchers – mainly in economics, anthropology, political science, and psychology – have begun to design research projects specifically to understand how exposure to the violence of war affects collective action, fairness, cooperation, and other important aspect of social behaviour among populations around the globe.

In a new paper, we discuss and reanalyse this rapidly growing body of research (Bauer et al. 2016). Figure 1 illustrates the breadth of evidence, referencing studies involving Sierra Leone, Uganda, Burundi, the Republic of Georgia, Israel, Nepal, and many other societies. The data come from individual surveys collected in seven countries, plus one paper with comparable data from 35 European countries. This evidence covers both civil and interstate wars and includes a wide array of wartime violence experiences.

Figure 1. Evidence on wartime violence and cooperation across the world

Note: The map reports the countries included in the analysis. The shading corresponds to the number of observations, such that darker colours represent larger samples of individuals.

Case study: Sierra Leone

As an example, we first describe the case of Sierra Leone, a post-conflict society for which there is an unusual wealth of evidence. A brutal, countrywide civil war afflicted Sierra Leone from 1991 to 2002. The war killed more than 50,000 civilians and temporarily displaced roughly two million people—nearly half of the country’s population. Armed groups mutilated and raped thousands of civilians. Nonetheless, there was wide variation in the degree of exposure and victimisation.

Three studies from Sierra Leone identified the same essential pattern – plausibly exogenous variation in exposure to war-related violence was associated with greater social participation and prosocial behaviour. Bellows and Miguel (2009) analysed a large-scale nationally representative survey dataset gathered among more than 10,000 Sierra Leone households three to five years after the conflict’s end. Victimisation rates were high; for instance, 44% of respondents reported a household member being killed during the conflict. They found that people whose households directly experienced war violence displayed much higher levels of civic and political engagement compared to non-victims – they were more likely to report attending community meetings, to vote in elections, to join social and political groups, and to participate in school committees and ‘road brushing,’ a local infrastructure maintenance activity.

Researchers have also carried out incentivised lab-in-the-field experiments, in order to more directly assess whether war-related violence causes changes in social preferences or in beliefs about others’ behaviour. Bauer et al. (2014) ran various allocation games designed to distinguish selfishness from altruism and inequality aversion. They experimentally manipulated the identity of an otherwise anonymous recipient to shed light on whether violence increases prosocial behaviour only towards people at the local level (from the same village), or whether the effects on prosocial behaviour are more generalised. Compared to non-victims, people who were directly exposed to conflict-related violence were less selfish and more inequality averse towards in-group members eight years after experiencing war-related violence. There were no comparable effects on behaviour towards out-group members. Elsewhere in Sierra Leone, Cecchi et al. (2015) found similar results among young street football players. Players who had been exposed to more intense conflict-related violence behaved more altruistically towards their teammates (the in-group) but not towards the out-group (their match opponents).

Evidence on the effects of exposure to wartime violence

We identified 19 studies that focus on the effects of war violence on social behaviour and performed a meta-analysis of 16 of these for which original data are available. The outcome variables generally fall into six categories – social group participation, community leadership and participation, trust, prosocial behaviour in experimental games, voting, and knowledge of and interest in politics.

The evidence suggests that war affects behaviour in a range of situations (Figure 2).  People exposed to more war-related violence tend to increase their social participation, by joining more local social and civic groups, or taking on more leadership roles in their communities. They also take actions intended to benefit others in experimental laboratory games, such as altruistic giving. The effects of violence are fairly consistent across cases and do not diminish with time. Violence seems to affect in-group prosocial behaviour – namely, participation with, and altruism towards, members of one’s own village or identity group – most of all (Figure 3). Too few studies define ‘out-groups’ consistently (or at all), so this in-group bias remains somewhat speculative.

Figure 2. Meta-analysis results, war exposure and cooperation

Note: The effect of exposure to violence on each outcome is estimated using fixed-effects (blue) and random-effects (green) meta-analysis models. Results are reported in standard deviation units. The vertical lines denote 95% confidence intervals. N denotes the number of studies/games included in the meta-analysis for each outcome.  

Figure 3. Meta-analysis results, in-group versus out-group effects

Disentangling correlation and causation

Notice that a common feature of this body of research is that analysis is based on a comparison of individuals who suffered different degrees of war violence. The obvious concern is the possibility that the correlation between war exposure and cooperation is driven by some omitted variable that has a confounding effect, rather than reflecting a causal impact. For instance, attackers may systematically target people who are likely to be more cooperative in nature, such as leading families or wealthy and influential citizens.

Studies in this area have taken various analytical steps to mitigate some of the most worrisome confounders – controlling for village fixed effects and thus removing potential regional and local omitted variables, controlling for an extensive set of pre-war characteristics, or estimating effects among sub-samples for which victimisation was likely to be less systematic. In the meta-analysis we show the results are relatively consistent across different studies and approaches to causal identification, arguably generating more confidence that the estimated relationships are causal.


Understanding the effects of war in all its complexity, including on post-war patterns of individual social behaviour, is of broad importance. While war has many negative legacies for individuals and societies, it appears to leave a positive legacy in terms of local cooperation and civic engagement. The core empirical finding we identify resonates with the experience of rapid post-war political, social, and economic recovery in many war-torn societies, as well as their tendency to implement egalitarian social policies, including progressive taxation and gender equality reforms (Tripp 2015, Scheve and Stasavage 2010, 2012). Yet if people become more parochial and less cooperative with out-group members, as some of the evidence suggests, this behavioural response could also harden social divisions, contribute to conflict cycles, and help explain the well-known pattern that many post-conflict countries soon return to violence.


Bauer, M, A Cassar, J Chytilová and J Henrich (2014) “War’s enduring effects on the development of egalitarian motivations and in-group biases”, Psychological Science, 25(1): 47–57.

Bauer, M, C Blattman, J Chytilová, J Henrich, E Miguel and T Mitts (2016) "Can war foster cooperation?", Journal of Economic Perspectives, forthcoming.

Bellows, J and E Miguel (2009) “War and local collective action in Sierra Leone”, Journal of Public Economics, 93(11): 1144–57.

Blattman, C and E Miguel (2010) “Civil war”, Journal of Economic Literature, 48(1): 3–57.

Bowles, S (2008) “Being human: Conflict: Altruism’s midwife”, Nature, 456(7220): 326–27.

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Cecchi, F, K Leuveld and M Voors (2016) “Conflict exposure and competitiveness: Experimental evidence from the football field in Sierra Leone”, Economic Development and Cultural Change, 64(3): 405-435.

Choi, J-K and S Bowles (2007) “The coevolution of parochial altruism and war”, Science, 318(5850): 636–40.

Collier, P, V L Elliott, H Hegre, A Hoeffler, M Reynal-Querol and N Sambanis (2003) Breaking the conflict trap: Civil war and development policy, World Bank Publications.

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Flannery, K V and J Marcus (2003) “The origin of war: New 14C dates from Ancient Mexico”, Proceedings of the National Academy of Sciences, 100(20): 11801–5.

Morris, I (2014) War! What is it good for? Conflict and the progress of civilization from primates to robots, Farrar Straus & Giroux.

Scheve, K and D Stasavage (2010) “The conscription of wealth: Mass warfare and the demand for progressive taxation”, International Organization, 64(04): 529–61.

Scheve, K and D Stasavage (2012) “Democracy, war, and wealth: Lessons from two centuries of inheritance taxation”, American Political Science Review, 106(01): 81–102.

Tilly, C (1985) “War making and state making as organized crime”, in Bringing the state back in, Cambridge University Press.

Tripp, A M (2015) Women and power in post-conflict Africa, Cambridge University Press.

Turchin, P (2015) Ultrasociety: How 10,000 years of war made humans the greatest cooperators on Earth, Beresta Books.


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