The idea of war and conflict as a driver of cooperation has regularly been discussed in this blog, and it is often assumed that people help one another in times of adversity, especially when in conflict with other groups. Inter-group conflict has been widely suggested as a key mechanism in the evolution of uniquely large-scale cooperation in humans. Specifically, several models based on cultural and genetic group selection propose that groups in which people are altruistic towards their fellow group members and hostile to outsiders are more likely to be victorious in inter-group conflict.
From an empirical perspective, there are two main ways of testing this idea. One can look at the past for evidence that more altruistic groups out-competed less altruistic ones through inter-group conflict. There have been some indirect attempts to do this, notably Bowles (2009), which showed that the levels of inter-group warfare in the Late Pleistocene and early Holocene were likely to be high enough to enable selective pressures required for the evolution of altruistic behaviours. Alternatively, one can look at the present and test whether inter-group conflict is associated with increased levels of altruism towards the in-group, and this was what my recent paper with Ruth Mace attempted to do.
We measured cooperative behaviour between and within two groups with a long and on-going history of conflict: Catholic and Protestant communities in Northern Ireland. We quantified cooperative behaviour using naturalistic measures: donations to schools and charity, and lost letters experiments. In the donations experiment, we ran a door-to-door survey with questions about individual exposure to conflict, such as the number of times people had experienced sectarian attacks. We also offered people £5 for their time in answering the survey, and allowed them to keep or donate the money to a local primary school, which was either a Catholic or Protestant school, or to a neutral charity, Save the Children (people were only given one randomly selected choice). This experiment was, in essence, a surreptitious dictator game and allowed us to measure in-group, out-group and unbiased cooperation. In the lost letters experiment, we dropped stamped letters on the pavement addressed to fictional Catholic, Protestant, and neutral charities (CatholicAID, ProtestantAID and CancerAID) and measured the neighbourhood’s cooperative behaviour by the amount of letters returned, similar to the original Stanley Milgram 1960’s experiments.
We expected to find that exposure to conflict would result in increased levels of cooperation towards the in-group and reduced levels towards the out-group, in what is often referred to as parochial altruism. Although we found that increased exposure to conflict did reduce the likelihood of donating to out-group schools and returning out-group letters, it had no effect on helping the in-group through either donations or lost letters returns. However, we did find that individuals’ and neighbourhoods’ socio-economic characteristics were the best predictors of cooperative behaviour. Wealthy people were much more likely to give money to in-group schools and people in wealthy neighbourhoods were also more likely to return an in-group letter. Interestingly, wealth had no effect in the cooperative behaviour toward the out-group.
In the paper, we discuss possible reasons behind these results. One possibility is that high status individuals are more likely to invest in conflict because, in these situations, they have more to gain and lose (as recently modelled by Gavrilets & Fortunato 2014). Here, I would like to discuss another possibility: that individuals may not be necessarily behaving altruistically in situations of conflict. Our study was only based on two measures – and others have indeed found some association between conflict and cooperation – but perhaps there are more evolutionarily parsimonious explanations for the behaviour of individuals during wartime, such as reputation concerns and enforcement mechanisms. For example, a quick look at large-scale conflicts with high casualty numbers and where good recruitment data is available does indicate the importance of enforcement in conflict. In WW2, 61% of all US servicemen were forced to fight in the war as draftees; in the UK, almost every man between 18 and 41 years old was forced to enlist. In Vietnam, despite only 25% of soldiers being draftees, a disproportionate 35% of the casualties were of drafted soldiers. In this case, the volunteers (non-drafted soldiers) were not necessarily ready and willing to fight for their country, but by volunteering they were able to choose their assignment, avoiding the most dangerous sections such as the infantry, which was then mostly composed of draftees. A recent review of inter-group warfare in small scale societies also found that individual benefits – mostly related to reputation and status – better explained intensity of conflict than group-level benefits, again demonstrating how individual altruism may not be an important motivation for conflict. These examples are not conclusive evidence for whether individual altruism plays a key role in conflict or not, but they suggest that perhaps we are too quick to attribute altruistic tendencies to individuals in situations of war.
The idea of altruism originating from war is perversely attractive. Yet, the empirical question of whether wars are, in fact, won because group members are more willing to sacrifice themselves for the group has not been satisfactorily answered. Mathematical models neatly draw out the battle-lines for alternative accounts for the evolution of unique cooperative tendencies. But it is only through continued empirical work – ideally using real world groups and naturalistic measures of cooperation – that we can settle on a shared conclusion.
National WWII Museum. Profile of US Servicemen (1941-1945). URL: http://www.nationalww2museum.org/learn/education/for-students/ww2-history/ww2-by-the-numbers/us-military.html
The American War Library (1997). Vietnam War Casualties by Volunteer or Drafted, Enlisted. URL: http://www.americanwarlibrary.com/vietnam/vwc8.htm
Wikipedia (2014). Conscription in the United States – Vietnam_War. URL: