Sentiment contagion dilutes prisoner's dilemmas on social networks

How to stabilize cooperation is an enduring conundrum in social sciences. Recent observations show that cooperation often emerges among individuals who are governed by irrationalism, such as moods, sentiments or feelings. Motivated by this fact, we propose a model where players imitate the sentiment of better-performing neighbours rather than their strategies on social networks. Three types of emotions reside and compete in the system, namely positive, neutral as well as negative moods, respectively. And based on the theory of empathy, we assume that players are more likely to cooperate with those having similar emotional patterns. Intriguingly, the system would eventually evolve to single-mood dynamics irrespectively of the initial moods combinations. By this mechanism, cooperation can be maintained at an acceptable level even under extremely adverse conditions such as in prisoner's dilemmas. Moreover, negative moods will be completely excluded if neutral players are biased towards positive ones, which thus further facilitates cooperation. This work might help explore “irrational” methods to solve stubborn social dilemmas of human society.