Non-cooperative game theory

Last updated

In game theory, a non-cooperative game is a game in which there are no external rules or binding agreements that enforces the cooperation of the players. on-cooperative it is typically used to model a competitive environment. This is stated in various accounts most prominent being John Nash's 1951 paper in the journal Annals of Mathematics . [1]

Contents

Counterintuitively, non-cooperative game models can be used to model cooperation as well, and vice versa, cooperative game theory can be used to model competition. Some examples of this would be the use of non-cooperative game models in determining the stability and sustainability of cartels and coalitions. [2] [3]

The difference between cooperative and non-cooperative game theory

According to Nash, the difference between cooperative game theory and non-cooperative game theory is that “(cooperative game) theory is based on an analysis of the interrelationships of the various coalitions which can be formed by the players of the game. Our (non-cooperative game) theory, in contradistinction, is based on the absence of coalitions in that it is assumed that each participant acts independently, without collaboration or communication with any of the others.” [4]

Non-cooperative game theory models different situations in which agents are unable to reach a resolution to a conflict that enforces some action on one another. [5] [6] This form of game theory pays close attention to the individuals involved and their rational decision making. [7] There are winners and losers in each case, and yet agents may end up in Pareto-inferior outcomes, where every agent is worse off and there is an potential outcome for every agent to be better off. [8] Agents will have the ability to predict what their opponents will do. Cooperative game theory models situations in which a binding agreement is possible. In other words, the cooperative game theory implies that agents cooperate to achieve a common goal and they are not necessarily referred to as a team because the correct term is the coalition. Each agent has its skills or contributions that provide strength to the coalition. [9]

Further, it has been supposed that non-cooperative game theory is purported to analyse the effect of independent decisions on society as a whole. [10] In comparison, cooperative game theory focuses only on the effects of participants in a certain coalition, when the coalition attempts to improve the collective welfare. [10]

Many results or solutions proposed by the agents involved in Game Theory are important in understanding the rivalry between these agents under a set of conditions that are strategic. [5]

Elements of a non-cooperative game

To specify a non-cooperative game completely, one must specify

  1. The number of players,
  2. The actions available to each player at any given state of the game,
  3. The function that each player is attempting to maximize,
  4. The time ordering of actions (if needed),
  5. How information is acquired by the players.
  6. Whether there is any randomness in the game. [11]

The following assumptions are commonly made:

  1. Perfect recall: each player remembers their decisions and known information. [6]
  2. Self-interest : each player does not consider the effect of actions on the others but only on their own. [6]
  3. Rational : each player is interested to maximise their utility or payoff. [12] [13]
  4. Complete information : each player knows the preferences and strategies of the other players. [12]
  5. Each player has the same understanding of how the game is. [12]

Examples

Strategic games are a form of non-cooperative game, where only the available strategies and combinations of options are listed to produce outcomes.

Rock paper scissors

Rock paper scissors.jpg

In the game of rock-paper-scissors, if Player 1 decides to play "rock", it is in Player 2's interest to play "paper"; if Player 2 chooses to play "paper", it is in Player 1's interest to play "scissors"; and if Player 1 plays "scissors", Player 2 will, in their own interests, play "rock".

Prisoner's Dilemma

A standard form Prisoner's Dilemma game. Prisoner's Dilemma.jpg
A standard form Prisoner's Dilemma game.

The Prisoner's Dilemma game is another well-known example of a non-cooperative game. The game involves two players, or defendants, who are kept in separate rooms and thus are unable to communicate. Players must decide, by themselves in isolation, whether to cooperate with the other player or to betray them and confess to law authorities. As shown in the diagram, both players will receive a higher payoff in the form of a lower jail sentence if they both remain silent. If both confess, they receive a lower payoff in the form of a higher jail sentence. If one player confesses and the other remain silent and cooperates, the confessor will receive a higher payoff, while the silent player will receive a lower payoff than if both players cooperated with each other.[ citation needed ]

The Nash equilibrium therefore lies where players both betray each other, in the players protecting oneself from being punished more.

The battle of the sexes

The game involves two players, boy and girl, deciding either going to a football game or going to an opera for their date, which respectively represent boy's and girl's preferred activity (i.e. boy prefers football game and girl prefers opera). [14] This example is a two-person non-cooperative non-zero sum (TNNC) game with opposite payoffs or conflicting preferences. [14] Because there are two Nash equilibria, this case is a pure coordination problem with no possibility of refinement or selection. [12] Thus, the two players will try to maximise their own payoff or to sacrifice for the other and yet these strategy without coordination will lead to two outcomes with even worse payoffs for both if they have disagreement on what to do on their date.

The battle of the sexes game
Boy/ GirlFootballOpera
Football(2, 1)(-1, -1)
Opera(-1, -1)(1, 2)

Matching pennies game

This game is a two-person zero-sum game. In order to play this game, both players will each need to be given a fair two-sided penny. To start the game, both player will each choose to either flip their penny to heads or tails. This action is to be done in secrecy and there should be no attempt at investigating the choice of the other player. After both players have confirmed their decisions, they will simultaneously reveal their choices. This concludes the actions taken by the players to determine the outcome. [15]

The win condition for this game is different for both players. For simplicity in explanation, lets denote the players as Player 1 and Player 2. In order for Player 1 to win, the faces of the pennies must match (This means they must both be heads or tails). In order for Player 2 to win, the faces of the pennies must be different (This means that they must be in a combination of heads and tails). [15]

The payoff/prize of this game is receiving the loser's penny in addition to your own.

Therefore the payoff matrix will look like this:

Player1 \ Player 2HeadsTails
Heads1, -1-1, 1
Tails-1, 11, -1

Looking at this matrix, we can conclude a few basic observations. [15]

  1. For all scenarios, there will be a loser and a winner.
  2. This is a zero sum game where the pay out to the winner is equal to the loss of the loser.
  3. There is no Pure Strategy Nash Equilibrium.

Analysis

Non-cooperative games are generally analysed through the non-cooperative game theory framework, which attempts to predict players' individual strategies and payoffs and in order to find the Nash equilibria. [16] [17] This framework often requires a detailed knowledge in the possible actions and the levels of information of each player. [7] It is opposed to cooperative game theory, which focuses on predicting which groups of players ("coalitions") will form, the joint actions that these groups will take, and the resulting collective payoffs that arise. Cooperative game theory does not analyse the strategic bargaining that occurs within each coalition and affects the distribution of the collective payoff between the members. Further in contrast to cooperative game theory, it is assumed that players involved have prior knowledge of their game in which they are involved, due to built in commitments. [18]

Non-cooperative game theory provides a low-level approach as it models all the procedural details of the game, whereas cooperative game theory only describes the structure, strategies and payoffs of coalitions. Therefore, cooperative game theory is referred to as coalitional, and non-cooperative game theory is procedural. [7] Non-cooperative game theory is in this sense more inclusive than cooperative game theory.

It is also more general, as cooperative games can be analysed using the terms of non-cooperative game theory where arbitration is available to enforce an agreement, that agreement falls outside the scope of non-cooperative theory: but it may be possible to state sufficient assumptions to encompass all the possible strategies players may adopt, in relation to arbitration. This will bring the agreement within the scope of non-cooperative theory. Alternatively, it may be possible to describe the arbitrator as a party to the agreement and model the relevant processes and payoffs suitably.

Accordingly, it would be desirable to have all games expressed under a non-cooperative framework. But in many instances insufficient information is available to accurately model the formal procedures available to the players during the strategic bargaining process; or the resulting model would be of too high complexity to offer a practical tool in the real world. In such cases, cooperative game theory provides a simplified approach that allows analysis of the game at large without having to make any assumption about bargaining powers.

Additionally, we must also look at the limitations that the non-cooperative model may have. We can have a clearer picture when looking at the list of assumptions stated above. As already mentioned, there are many scenarios where perfect symmetry of information is not possible which therefore results in the decision making process to be flawed. [19]

Secondly, the assumption of self-interest and rationality could be argued. Arguments are made that being rational can result in the assumption of self-interest being invalidated and vice versa. One such example could be the reduction in profits and revenue in attempts to drive out competitors for a higher market share. This thus does not follow both of the assumptions as the player is concerned with the downfall of their opponent more than the maximisation of their profits. There is the argument to be made that although mathematically sound and feasible, it is not necessarily the best method of looking at real life economical problems that are more complex in nature. [19]

Solutions

Solutions in non-cooperative games are similar to all other games in game theory, but without the ones involved binding agreements enforced by the external authority. The solutions are normally based on the concept of Nash equilibrium, and these solutions are reached by using methods listed in Solution concept. Most solutions used in non-cooperative game are refinements developed from Nash equilibrium, including the minimax mixed-strategy proved by John von Neumann. [8] [13] [20]

See also

Related Research Articles

An evolutionarily stable strategy (ESS) is a strategy that is impermeable when adopted by a population in adaptation to a specific environment, that is to say it cannot be displaced by an alternative strategy which may be novel or initially rare. Introduced by John Maynard Smith and George R. Price in 1972/3, it is an important concept in behavioural ecology, evolutionary psychology, mathematical game theory and economics, with applications in other fields such as anthropology, philosophy and political science.

Game theory is the study of mathematical models of strategic interactions. It has applications in many fields of social science, and is used extensively in economics, logic, systems science and computer science. Initially, game theory addressed two-person zero-sum games, in which a participant's gains or losses are exactly balanced by the losses and gains of the other participant. In the 1950s, it was extended to the study of non zero-sum games, and was eventually applied to a wide range of behavioral relations. It is now an umbrella term for the science of rational decision making in humans, animals, and computers.

The prisoner's dilemma is a game theory thought experiment that involves two rational agents, each of whom can cooperate for mutual benefit or betray their partner ("defect") for individual reward. This dilemma was originally framed by Merrill Flood and Melvin Dresher in 1950 while they worked at the RAND Corporation. Albert W. Tucker later formalized the game by structuring the rewards in terms of prison sentences and named it the "prisoner's dilemma".

In game theory, the Nash equilibrium is the most commonly-used solution concept for non-cooperative games. A Nash equilibrium is a situation where no player could gain by changing their own strategy. The idea of Nash equilibrium dates back to the time of Cournot, who in 1838 applied it to his model of competition in an oligopoly.

In game theory, a cooperative game is a game with groups of players who form binding “coalitions” with external enforcement of cooperative behavior. This is different from non-cooperative games in which there is either no possibility to forge alliances or all agreements need to be self-enforcing.

A coordination game is a type of simultaneous game found in game theory. It describes the situation where a player will earn a higher payoff when they select the same course of action as another player. The game is not one of pure conflict, which results in multiple pure strategy Nash equilibria in which players choose matching strategies. Figure 1 shows a 2-player example.

Matching pennies is a non-cooperative game studied in game theory. It is played between two players, Even and Odd. Each player has a penny and must secretly turn the penny to heads or tails. The players then reveal their choices simultaneously. If the pennies match, then Even wins and keeps both pennies. If the pennies do not match, then Odd wins and keeps both pennies.

In game theory, a Bayesian game is a strategic decision-making model which assumes players have incomplete information. Players hold private information relevant to the game, meaning that the payoffs are not common knowledge. Bayesian games model the outcome of player interactions using aspects of Bayesian probability. They are notable because they allowed, for the first time in game theory, for the specification of the solutions to games with incomplete information.

In game theory, a dominant strategy is a strategy that is better than any other strategy for one player, no matter how that player's opponent will play. Some very simple games can be solved using dominance.

In game theory, a symmetric game is a game where the payoffs for playing a particular strategy depend only on the other strategies employed, not on who is playing them. If one can change the identities of the players without changing the payoff to the strategies, then a game is symmetric. Symmetry can come in different varieties. Ordinally symmetric games are games that are symmetric with respect to the ordinal structure of the payoffs. A game is quantitatively symmetric if and only if it is symmetric with respect to the exact payoffs. A partnership game is a symmetric game where both players receive identical payoffs for any strategy set. That is, the payoff for playing strategy a against strategy b receives the same payoff as playing strategy b against strategy a.

In game theory, folk theorems are a class of theorems describing an abundance of Nash equilibrium payoff profiles in repeated games. The original Folk Theorem concerned the payoffs of all the Nash equilibria of an infinitely repeated game. This result was called the Folk Theorem because it was widely known among game theorists in the 1950s, even though no one had published it. Friedman's (1971) Theorem concerns the payoffs of certain subgame-perfect Nash equilibria (SPE) of an infinitely repeated game, and so strengthens the original Folk Theorem by using a stronger equilibrium concept: subgame-perfect Nash equilibria rather than Nash equilibria.

In game theory, the outcome of a game is the ultimate result of a strategic interaction with one or more people, dependant on the choices made by all participants in a certain exchange. It represents the final payoff resulting from a set of actions that individuals can take within the context of the game. Outcomes are pivotal in determining the payoffs and expected utility for parties involved. Game theorists commonly study how the outcome of a game is determined and what factors affect it.

Quantal response equilibrium (QRE) is a solution concept in game theory. First introduced by Richard McKelvey and Thomas Palfrey, it provides an equilibrium notion with bounded rationality. QRE is not an equilibrium refinement, and it can give significantly different results from Nash equilibrium. QRE is only defined for games with discrete strategies, although there are continuous-strategy analogues.

In game theory, an epsilon-equilibrium, or near-Nash equilibrium, is a strategy profile that approximately satisfies the condition of Nash equilibrium. In a Nash equilibrium, no player has an incentive to change his behavior. In an approximate Nash equilibrium, this requirement is weakened to allow the possibility that a player may have a small incentive to do something different. This may still be considered an adequate solution concept, assuming for example status quo bias. This solution concept may be preferred to Nash equilibrium due to being easier to compute, or alternatively due to the possibility that in games of more than 2 players, the probabilities involved in an exact Nash equilibrium need not be rational numbers.

In game theory, the traveler's dilemma is a non-zero-sum game in which each player proposes a payoff. The lower of the two proposals wins; the lowball player receives the lowball payoff plus a small bonus, and the highball player receives the same lowball payoff, minus a small penalty. Surprisingly, the Nash equilibrium is for both players to aggressively lowball. The traveler's dilemma is notable in that naive play appears to outperform the Nash equilibrium; this apparent paradox also appears in the centipede game and the finitely-iterated prisoner's dilemma.

In game theory, a strong Nash equilibrium(SNE) is a combination of actions of the different players, in which no coalition of players can cooperatively deviate in a way that strictly benefits all of its members, given that the actions of the other players remain fixed. This is in contrast to simple Nash equilibrium, which considers only deviations by individual players. The concept was introduced by Israel Aumann in 1959. SNE is particularly useful in areas such as the study of voting systems, in which there are typically many more players than possible outcomes, and so plain Nash equilibria are far too abundant.

Cooperative bargaining is a process in which two people decide how to share a surplus that they can jointly generate. In many cases, the surplus created by the two players can be shared in many ways, forcing the players to negotiate which division of payoffs to choose. Such surplus-sharing problems are faced by management and labor in the division of a firm's profit, by trade partners in the specification of the terms of trade, and more.

<span class="mw-page-title-main">Jean-François Mertens</span> Belgian game theorist (1946–2012)

Jean-François Mertens was a Belgian game theorist and mathematical economist.

In game theory, Mertens stability is a solution concept used to predict the outcome of a non-cooperative game. A tentative definition of stability was proposed by Elon Kohlberg and Jean-François Mertens for games with finite numbers of players and strategies. Later, Mertens proposed a stronger definition that was elaborated further by Srihari Govindan and Mertens. This solution concept is now called Mertens stability, or just stability.

The Berge equilibrium is a game theory solution concept named after the mathematician Claude Berge. It is similar to the standard Nash equilibrium, except that it aims to capture a type of altruism rather than purely non-cooperative play. Whereas a Nash equilibrium is a situation in which each player of a strategic game ensures that they personally will receive the highest payoff given other players' strategies, in a Berge equilibrium every player ensures that all other players will receive the highest payoff possible. Although Berge introduced the intuition for this equilibrium notion in 1957, it was only formally defined by Vladislav Iosifovich Zhukovskii in 1985, and it was not in widespread use until half a century after Berge originally developed it.

References

  1. ↑ Nash, John (1951). "Non-Cooperative Games". Annals of Mathematics. 54 (2): 286–295. doi:10.2307/1969529. JSTOR   1969529.
  2. ↑ Palsule-Desai, Omkar D. (March 2015). "Complete Versus Partial Collusion in Competing Coalitions". International Game Theory Review. 17 (1): 1540006. doi:10.1142/S021919891540006X.
  3. ↑ Carraro, Carlo, ed. (2003). The Endogenous Formation of Economic Coalitions. doi:10.4337/9781781009888. ISBN   978-1-78100-988-8.[ page needed ]
  4. ↑ Nash, John (1997). "3. Non-Cooperative Games. Annals of Mathematics 54 (1951) 286-295". Classics in Game Theory. pp. 14–26. doi:10.1515/9781400829156-008. ISBN   978-1-4008-2915-6.
  5. 1 2 Aguirre, Inaki (2023-04-24). "Non-Cooperative Game Theory" (PDF). Retrieved 2023-04-24.
  6. 1 2 3 Non-Cooperative Game Theory. Monographs in Mathematical Economics. Vol. 1. 2015. doi:10.1007/978-4-431-55645-9. ISBN   978-4-431-55644-2.[ page needed ]
  7. 1 2 3 Chatain, Olivier (2018). "Cooperative and Non-cooperative Game Theory". The Palgrave Encyclopedia of Strategic Management. pp. 345–346. doi:10.1057/978-1-137-00772-8_468. ISBN   978-0-230-53721-7.
  8. 1 2 "Noncooperative Games". Encyclopedia.com. Retrieved 2022-05-02.
  9. ↑ Hamidi, Maryam; Liao, Haitao; Szidarovszky, Ferenc (November 2016). "Non-cooperative and cooperative game-theoretic models for usage-based lease contracts". European Journal of Operational Research. 255 (1): 163–174. doi:10.1016/j.ejor.2016.04.064.
  10. 1 2 Non-Cooperative Game Theory. Monographs in Mathematical Economics. Vol. 1. 2015. doi:10.1007/978-4-431-55645-9. ISBN   978-4-431-55644-2.[ page needed ]
  11. ↑ Başar, Tamer (26 January 2010). "Lecture Notes on Non-Cooperative Game Theory" (PDF). Hamilton Institute and CTVR in Trinity College, Dublin, Ireland.
  12. 1 2 3 4 Aguirre, Iñaki. "Notes on Non-Cooperative Game Theory-Microeconomic Theory IV" (PDF).
  13. 1 2 von Neumann, John; Morgenstern, Oskar (2007). Theory of Games and Economic Behavior (Commemorative ed.). Princeton University Press. ISBN   978-0-691-13061-3. OCLC   1081636887.[ page needed ]
  14. 1 2 Biswas, Tapan (1997). Decision-Making under Uncertainty. doi:10.1007/978-1-349-25817-8. ISBN   978-0-333-66261-8.[ page needed ]
  15. 1 2 3 Non-Cooperative Game Theory. Monographs in Mathematical Economics. Vol. 1. 2015. doi:10.1007/978-4-431-55645-9. ISBN   978-4-431-55644-2.[ page needed ]
  16. ↑ Chandrasekaran, R. "Cooperative Game Theory" (PDF).[ self-published source? ]
  17. ↑ Brandenburger, Adam. "Cooperative Game Theory: Characteristic Functions, Allocations, Marginal Contribution" (PDF). Archived from the original (PDF) on 2016-05-27.[ self-published source? ]
  18. ↑ Van Damme, E. (2001). "Game Theory: Noncooperative Games". International Encyclopedia of the Social & Behavioral Sciences. pp. 5873–5880. doi:10.1016/B0-08-043076-7/02230-0. ISBN   978-0-08-043076-8.
  19. 1 2 Michaelides, Panayotis G.; Papadakis, Theodoulos Eleftherios (2023). History of Economic Ideas. doi:10.1007/978-3-031-19697-3. ISBN   978-3-031-19696-6.[ page needed ]
  20. ↑ v. Neumann, J. (December 1928). "Zur Theorie der Gesellschaftsspiele" [On the theory of board games]. Mathematische Annalen (in German). 100 (1): 295–320. doi:10.1007/bf01448847. S2CID   122961988.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.