In all populations individuals must struggle to balance their personal interest with sacrificing for the greater good of the whole. Viewed in terms of the Darwinian struggle for survival of the fittest, there is an evolutionary advantage to sacrificing selflessly (altruism), if that personal sacrifice provides one's genetically-related group an advantage. Think bees that lose their life when they sting a predator so that the hive can survive and pass on genes that are related to the defender. In other words, individuals sacrifice because there is a reward to their genetic heritage in doing so. By this reasoning, ethnic and religious diversity in a society should undermine cooperation, but does it? And if diversity does undermine cooperation and altruism, is there some way societies can overcome the animal instinct to flock with one's own kind. These are especially acute questions as barriers to travel fall, promoting diversity in countries around the globe, and as ethnically and religiously different groups of people clash around the world.
A study by political scientists Fotini Christia, at MIT and Marcus Alexander at Stanford University published in the December 9, 2011 issue of the journal Science exploited a unique situation in Bosnia-Herzegovina to find answers to these questions. The court ordered integration across ethnic lines separating Christians and Muslims in two of the four high schools in Mostar, Bosnia-Herzegovina, allowed researchers to study the effects of ethnic diversity and forced integration on altruism. Since the integration was compulsory in the two integrated schools, the results were not biased by issues of self selection.
In these studies, students participated in a computer-based public-good game, in which each player in a group of four contributed money to the public treasury. After everyone contributes, the pot is divided up and distributed equally among all players regardless of how much each player contributed. In one scenario, free-loaders who contribute nothing will have the greatest individual success. In contrast to the stingy approach, if everyone generously gave away all of their money, this would provide the maximum benefit to the group as a whole once the pot was split equally.
So to make the situation more interesting by encouraging individuals to act in a self-less manner for the maximum benefit to the group, sanctions were imposed on those who contributed the least. The amount of sanctions to be imposed was determined after players were informed of the level of contribution made by the other players. Since other players will soon learn how much an individual contributes, each player is in a way communicating to others how much of their wealth they feel should be provided for public good. A "stingy" group of players might settle on an average of say a 10% contribution of their individual funds to the pot, and a "generous" group of players might settle on a donation of 30%. Thus, researchers have a numerical measure of how altruistic different groups of players are.
What the researchers found was that when groups of players were from diverse backgrounds, that is, a mixture of Christians and Muslims, the individuals contributed less to the pot. Diversity decreases altruism. The negative effect of diversity was quite large, cutting contributions to 1/3 of the amount contributed when the individuals were playing in groups that were composed of ethnically homogenous members (Christians with Christians and Muslims with Muslims). This outcome fits perfectly with Darwinian thinking.
Now, what if the players had come from an integrated or a segregated school? The researchers found that if the players had come from integrated high schools, contributions were not much different when they played in mixed or segregated groups.
Sanctions had a very different effect on contributions, depending on whether the players came from integrated or segregated schools. If students had come from integrated schools, costly sanctions had a large effect in increasing altruism regardless of whether they played in homogenous or mixed groups, but when subjects were from segregated schools, sanctions had no effect on contribution to public good, regardless of whether they played in homogenous or racially mixed groups. Sanctions, the authors suggest, don't seem to work in a homogenous society because there is a high sense of intra-group kinship that reduces the threat of sanctioning.
If these results can be extrapolated beyond this uniquely war-torn society, it can be concluded that diversity reduces individual contributions to the public good, but only when individuals come from segregated schools. In contrast, when individuals come from integrated institutions, the difference in contributions to public good in homogenous and racially/religiously mixed groups is eliminated. Thus, human beings have within their power the ability to modify the animal-based instinct that undermines cooperation among diverse populations by implementing social measures, and this should promote better-ordered and more cooperative societies.