Study on Evolution of Cooperation by an Asymmetric Population
Game on Complex Networks
JIANG Yanmei, TIAN Yuping
School of Automation, Southeast University, Nanjing, 210096,P. R. China
E-mail: jiangyanmei0619@126.com, yptian@seu.edu.cn
Abstract: This paper studies on the evolution of cooperation by an asymmetric population game on complex networks. By
designing an asymmetric population game on different complex networks and with the help of Matlab simulation, we find that
the cooperation evolution of this population game depends on three important factors: cost-to-benefit of SD-type players (r
2
),
the number of PD-type players (n
PD
), and the average degrees of complex networks (<k>). The simulation results reveal
several facts. For small r
2
(r
2
< 0.6) and the given n
PD
, neither regular networks nor BA scale-free networks are in favor of
cooperation. And the smaller the average degree is, the less cooperation in the game becomes. However, for large r
2
(r
2
> 0.6)
and the given n
PD
, both regular networks and BA scale-free networks are conducive to cooperation. Further more, the smaller
average degree is, the more cooperation becomes.
Key Words: Evolution of Cooperation, Asymmetric Population Game, Complex Networks
1 Introduction
Cooperation plays an important role in the evolution of
species. The cooperation phenomena exist widely in the na-
ture [1-3]. Evolutionary game theory [4-5] has become a
powerful tool to investigate theses phenomena, and research
on cooperation mechanisms becomes more and more sig-
nificant. Besides, two simple games, the Prisoner’s Dilem-
ma game (PDG) [6] and the snowdrift game (SDG) [7]
have been used widely in theoretical and experimental stud-
ies. Based on the achievement in the past, Nowak pointed
out five mechanisms which are conducive to the evolution
of cooperation [8]: kin selection, direct reciprocity, indirec-
t reciprocity, group selection, and network reciprocity. The
effect of spatial structures on cooperation evolution in the
population games has been studied for a long time. In the
literatures [9-10], Nowak et al. studied Prisoner’s Dilem-
ma game on regular lattices where every agent has different
number of the neighbors; their research showed that the spa-
tial structures of regular networks can promote cooperation
in the population game. Meanwhile spatial structures can
also do a contrary effect on the snowdrift game. The result-
s in literature [11] manifested that spatial structures reduce
the proportion of cooperators for a wide range of parameters.
But fortunately, scale-free networks provide both PDGand
SDG a unifying framework for the emergence of coopera-
tion [12].
However, the studies mentioned above are all based on
symmetric population game, in which two players are cho-
sen to play a game, their payoff matrixes are identical. As
we all know, players often obtain different benefits even they
adopt the same strategy in a game, the asymmetric of payoff
exists commonly in practice [13]. And such a game can be
established as an asymmetric game. In the literature [14], the
authors researched the evolution of cooperation in an asym-
metric well-mixed population game. When the agents are
either PD-type agents or SD-type agents, the proportion of
This work is supported by National Natural Science Foundation (NNS-
F) of China under Grant 61273110 and 61573105, and the Research
Fund for the Doctoral Program of Higher Education of China under grant
20130092130002.
cooperators is determined by two factors: the numbers of
PD-type players and the parameters in SD-type players’ pay-
off matrixes. When the number of PD-type players is less
than a threshold value, equilibrium of the well-mixed popu-
lation game achieves 1 − r
2
. Nevertheless, population game
on complex networks is more common in the nature. It is
an urgent task to study on the evolution of cooperation by an
asymmetric population game on complex networks.
Inspired by the literature [14], we study on the evolution
of cooperation by an asymmetric population game on the
complex networks. By using Matlab simulation, the propor-
tion of cooperators in the population game on different av-
erage degrees of different complex networks is studied. The
simulations reveal that the cooperation evolution of a struc-
tured population game is determined by three important fac-
tors: the number of PD-type players (n
PD
), cost-to-benefit
of SD-type players (r
2
), and the average degrees of complex
networks (<k>). With increasing of the first two factors,
cooperation is hindered in general. However, the last factor
can promote the evolution of cooperation in the population
game under some certain conditions. Concretely speaking,
for the given n
PD
it is more favorable to cooperation in the
population game if the cost-to-benefit of SD-type players is
smaller. For given r
2
and <k>, with the PD-type player-
s’ number growth, cooperation in the population is hampered
by n
PD
after a certain threshold. Besides, for the given n
PD
, neither regular networks nor BA scale-free networks are in
favor of cooperation with small r
2
. And the smaller the aver-
age degree is, the less cooperation in the game becomes. But
for the given n
PD
, both regular networks and BA scale-free
networks are conducive to cooperation with large r
2
. What
is more, the smaller average degree is, the more cooperation
becomes.
The rest of the paper is organized as follows. The sys-
tem model is put forward in the section 2. The experimental
design and the experimental results are presented Section 3.
And concluding remarks are stated in the Section 4.
2 The Model
Generally speaking, a structured population evolutionary
game consists of the player set, strategy set, payoff matrix,
Proceedings of the 35th Chinese Control Conference
Jul
27-29, 2016, Chen
du, China
10339