Cooperation

==The prisoner's dilemma==
{{Main article|Prisoner's dilemma}}
The prisoner's dilemma is a model that demonstrates how, in certain conditions, members of a group will not cooperate even though cooperation would mutually benefit them all. It makes clear that collective self-interest is insufficient to achieving cooperative behavior, at least when an uncooperative individual who "cheats" can exploit cooperating group members. The prisoner's dilemma formalizing this problem using [[game theory]] and has been the subject of much theoretical and experimental research. The first extensive experimental studies were conducted in the early 1960s by [[Anatol Rapoport]] and Albert Chammah.<ref>Rapoport, A., & Chammah, A. M. (1965). Prisoner’s Dilemma: A study of conflict and cooperation. Ann Arbor, MI: University of Michigan Press.</ref> Results from [[experimental economics]] show that humans often act more cooperatively than strict self-interest, modeled as the Nash Equilibrium, would seem to dictate. While economic experiments require subjects to make relatively abstract decisions for small stakes, evidence from natural experiments for high stakes support the claim that humans act more cooperatively than strict self-interest would dictate.<ref>{{cite journal | author=van den Assem, van Dolder, and Thaler | title=''Split or Steal''? Cooperative Behavior when the Stakes are Large|year=2012 | ssrn=1592456}}</ref>

One reason may be that if the prisoner's dilemma situation is repeated (the [[Prisoner's dilemma#The iterated prisoner's dilemma|iterated prisoner's dilemma]]), it allows non-cooperation to be punished more, and cooperation to be rewarded more, than the single-shot version of the problem would suggest. It has been suggested that this is one reason for the evolution of complex [[emotion]]s in higher life forms.<ref>{{cite journal | author=Olsen, Harrington, and Siegelmann | title=Conspecific Emotional Cooperation Biases Population Dynamics: A Cellular Automata Approach|year=2010 | url=https://scholar.google.com/scholar?q=Conspecific+Emotional+Cooperation+Biases+Population+Dynamics:+A+Cellular+Automata+Approach&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&sa=N&hl=en&tab=ws}}</ref><ref>{{cite journal | author=Harrington, Olsen, and Siegelmann | title=Communicated Somatic Markers Benefit the Individual and the Species|year=2011}}</ref> Playing the iterated version of the game leads to a cascade of [[brain]] signals that relate the speed with which players reciprocate cooperation at subsequent rounds.<ref>{{cite journal | author=Cervantes Constantino, Garat, Nicolaisen, Paz, Martínez-Montes, Kessel, Cabana, and Gradin | title=Neural processing of iterated prisoner's dilemma outcomes indicates next-round choice and speed to reciprocate cooperation| journal=Social Neuroscience|year=2021 | volume=16| issue=2| pages=103–120| doi=10.1080/17470919.2020.1859410| pmid=33297873| s2cid=228087900| url=https://doi.org/10.1080/17470919.2020.1859410}}</ref>