Abstract
We propose a mechanism allowing strategy diversity instead of a common combination of cooperation and defection to study how cooperation evolves in public goods games. Each individual is assigned a variable valued in the unit interval as its cooperation degree. Thus, diverse cooperation degrees express the diversity of game strategies in the way of multiple contributions of players, and the investment in the common pool is positively correlated with cooperation degrees correspondingly. Moreover, we also define two particular roles named altruist and egotist defined locally since they depend on the behavior of their neighboring players. Numerical simulations show that the proposed diversity of strategies can substantially evoke the emergence and maintenance of cooperation. Notably, we also find that no player will act as a long-term exploiter (egotist) or exploitee (altruist) in the whole evolutionary process.