This project began in 2020 and has been a huge effort to assemble and harmonize so many datasets. I hope the paper and app will be useful to others as we keep pushing toward a more cumulative, collaborative science of conflict and its legacies.

Last but not least, thanks to Lee Guantai and Dino Kolonic for stellar data support and to all colleagues who shared replication materials and data, publicly or directly. This microdata meta-analysis exists only thanks to open science and transparency in the social sciences. 🙌

You can explore the results in this interactive Shiny app: joanbarcelosoler.shinyapps.io/wartime_effe...
. You can also plug in your own results (violence exposure → outcome) to see how they compare and how they would change the pooled estimate.

Takeaway: rebuilding engagement, trust, and cooperation, especially across wartime enemies, cannot be assumed to happen organically once violence stops. It requires targeted interventions that reduce hostility and actively foster reconciliation between antagonistic groups.

The picture that emerges challenges the idea that war can knit societies together. Instead, violence can increase participation within groups while deepening divides between them, reinforcing entrenched mistrust and polarization highlighted in the conflict trap thesis.

Fourth, when it comes to broader attitudes unrelated to the wartime enemy, evidence is weak. Wartime exposure does not reliably increase authoritarianism, intolerance, or hawkish security preferences, aside from some modest institutional mistrust.

Third: wartime exposure strengthens attachment to one’s own group. Individuals become more likely to trust people on their side, identify with them, and support them politically. Ingroup ties harden at the same time that outgroup distrust grows.

Second finding: hostility toward wartime adversaries consistently increases. People exposed to violence show more animosity, more fear, and more discriminatory behavior toward former opponents, and these patterns hold across violence types, contexts, and measurement strategies.

The often cited idea that war builds prosociality, trust, and engagement does not hold up well in this larger evidentiary base. Many positive findings in earlier work appear inconsistent, weak, or explained by recall and publication biases.

First big takeaway: the effects on civic engagement and prosocial behavior are mixed. Violence can push people into social groups or political mobilization, but it does not reliably boost generalized trust, altruism, voting, political interest, or prosocial norms.

This study synthesizes data from 172 quantitative studies across more than 50 countries to understand how wartime violence shapes attitudes and behavior long after conflicts end. The results challenge many optimistic assumptions about postwar social and political life.