Learn good from bad: Effects of good and bad neighbors in spatial prisoners’ dilemma games

• People learn to be good with bad neighbors while bad with good ones.
• Harsh environment encourages people to seek a better life via self-organizing.
• Selfish neighbors or even scoundrels are preferred to enhance cooperation.
• The key of enhancing cooperation is a fair environment for interactions.

Cooperation is vital for the human society and this study focuses on how to promote cooperation. In our stratification model, there exist three classes: two minorities are elites who are prone to cooperate and scoundrels who are born to defect; one majority is the class of common people. Agents of these three classes interact with each other on a square lattice. Commons’ cooperation and its factors are investigated. Contradicting our common sense, it indicates that elites play a negative role while scoundrels play a positive one in promoting commons’ cooperation. Besides, effects of good and bad neighbors vary with temptation. When the temptation is smaller the positive effect is able to overcome the negative effect, but the later prevails when the temptation is larger. It concludes that common people are more prone to cooperate in harsh environment with bad neighbors, and a better environment with good neighbors merely leads to laziness and free riding of commons.