Heroes and Cowards demonstrates the role that social capital plays in people's decisions. The makeup of various companies--whether soldiers were of the same ethnicity, age, and occupation--influenced whether soldiers remained loyal or whether they deserted. Costa and Kahn discuss how the...

"We find that veterans of the Union Army who faced greater wartime stress (as measured by higher battlefield mortality rates) experienced higher mortality rates at older ages, but that men who were from more cohesive companies were statistically significantly less likely to be affected by...