To cooperate means to forfeit personal benefits for the common good. And although fundamental principles of biology and evolution would have you believe that cooperation is mostly at odds with how nature works, we humans owe our evolutionary success precisely and almost exclusively to our remarkable other-regarding abilities. We care for one another, and we work together to achieve what we would not be able to achieve alone. This important aspect of our biology has recently attracted also the attention of physicists [1,2]. But what can physics offer towards the solution of this puzzle?
It turns out that the Monte Carlo method, the method that was developed during the Manhattan Project by Stanislaw Ulam and John von Neumann to simulate the random behavior of neutrons in a nuclear chain reaction, can be used to determine the outcomes of social models that study cooperation, as well as other types of moral behavior. The backbones of these models are large social networks, in which agents adopt different strategies based on their past or expected success. The rules of interactions are most often determined by game theory, for example by the public goods game or other social dilemmas. The Monte Carlo method then allows us to obtain solutions to otherwise unsolvable models, which in turn empowers us to approach reality in greater detail and to take into consideration more of the essential features that are behind the complexity of human decision making. The solutions we can observe are truly fascinating, and in them physics again plays a pivotal role. In particular the theory of phase transition, which shows us how seemingly very different systems, across various magnitudes of scale and complexity, exhibit qualitatively the same behavior.
In simple terms, just as water starts to boil at 100 0C, so can a social system exhibit a phase transition from defection to cooperation at a critical reward value. And although cooperation and defection are not phases per se, as are solid, liquid, and the gas phase, the same theory nevertheless applies to them. What is more, these phase transitions can be continuous, which means that their onset is gradual and we can anticipate their consequences, or discontinuous, which means that they appear suddenly and largely out of the blue, and often with strikingly unexpected and counterintuitive consequences. Physics thus enables us to study and to better understand the often odd and unwanted outcomes of well-intended policies, and to simulate and predict the outcomes of alternatives that we hope might work better.
To conclude, most of the grandest challenges of our time, such as climate inaction, the depletion of natural resources, growing inequality, and perpetual conflicts in many parts of the world, are primarily of a societal nature. But their solutions will require insights from different fields of research, and social physics is in recent years emerging as an ever more important piece of this puzzle [3].
References
[1] Matjaž Perc et al., Statistical physics of human cooperation, Phys. Rep. 687, 1-51 (2017) doi: 10.1016/j.physrep.2017.05.004
[2] Marko Jusup et al., Social physics, Phys. Rep. 948, 1-148 (2022) doi: 10.1016/j.physrep.2021.10.005
[3] Matjaž Perc, The social physics collective, Sci. Rep. 9, 16549 (2019) doi: 10.1038/s41598-019-53300-4
Ph.D. in physics from the University of Maribor in 2006. He is currently Professor of Physics at the University of Maribor, staff researcher at the Community Healthcare Center Dr. Adolf Drolc Maribor, Adjunct Professor at Kyung Hee University and Korea University, and External faculty member at the Complexity Science Hub in Vienna. He is a member of Academia Europaea and the European Academy of Sciences and Arts, and among top 1% most cited physicists according to 2020, 2021, 2022, and 2023 Clarivate Analytics data. He is also the 2015 recipient of the Young Scientist Award for Socio and Econophysics from the German Physical Society, and the 2017 USERN Laureate. In 2018 he received the Zois Award, which is the highest national research award in Slovenia. In 2019 he became Fellow of the American Physical Society. Since 2021 he is Vice-Dean of Natural Sciences at the European Academy of Sciences and Arts in Salzburg.