Greenbeard Effect

Humans cooperate in groups in which mutual monitoring is common, and this provides the possibility of third-party arbitration. Third-party arbitration stabilizes reciprocity in at least two ways: first, when it is accurate, it reduces the frequency of misunderstandings resulting from perception errors, and second, even when it is inaccurate, it provides a public signal that allows pairs to align their expectations about how to behave after errors occur. Here, we describe experiments that test for these two effects. We find that in an iterated, sequential Prisoner's Dilemma game with errors, players with the highest average payoffs are those who make use of third-party arbitration and who also employ forgiving strategies. The combination of these two behaviours reduces the detrimental effects of errors on reciprocity, resulting in more cooperation.

The similarity discrimination effect occurs when a single gene or gene cluster causes its carriers to display both a variable phenotypic trait and a behavioural predisposition to cooperate preferentially with recognisably similar carriers. We distinguish this from the greenbeard effect, in which cooperation evolves through fixed phenotypic tags and genetically linked cooperative behaviour with others displaying the same tag. Our agent-based simulations show that the evolution of cooperation through similarity discrimination, in contrast to the greenbeard effect, does not depend on population viscosity or other restrictive conditions. Similarity discrimination evolves spontaneously in well mixed populations, not only in the Prisoner's Dilemma game but also across a range of different binary-choice strategic interactions, provided that agents can distinguish reliably between similar and dissimilar co-players.

• Defect is a dominant strategy • "Cheap talk": no enforceable commitments • A priori, communication should not alter prediction of mutual defection • Stark test for the impact of communication INTRODUCTION Objective Communication and Cooperation. Miller et al. (JEBO 2002) 7 / 36 • To gain insight into development and impact of endogenous communication • Focus on cooperation in a single-shot Prisoner's Dilemma INTRODUCTION Agenda

We present new results on the evolution of tag-mediated cooperation, demonstrating that the use of multidimensional tags can enhance the emergence of high levels of cooperation. We discuss these results in the context of prior cases in which work on the evolution of cooperation has led to practical techniques for improving the problem-solving performance of genetic programming systems.

The similarity discrimination effect occurs when a single gene or gene cluster causes its carriers to display both a variable phenotypic trait and a behavioural predisposition to cooperate preferentially with recognisably similar carriers. We distinguish this from the greenbeard effect, in which cooperation evolves through fixed phenotypic tags and genetically linked cooperative behaviour with others displaying the same tag. Our agent-based simulations show that the evolution of cooperation through similarity discrimination, in contrast to the greenbeard effect, does not depend on population viscosity or other restrictive conditions. Similarity discrimination evolves spontaneously in well mixed populations, not only in the Prisoner's Dilemma game but also across a range of different binary-choice strategic interactions, provided that agents can distinguish reliably between similar and dissimilar co-players.

We use the self-tuning Experience Weighted Attraction model with repeated-game strategies as a computer testbed to examine the relative frequency, speed of convergence and progression of a set of repeated-game strategies in four symmetric 2 × 2 games: Prisoner's Dilemma, Battle of the Sexes, Stag-Hunt, and Chicken. In the Prisoner's Dilemma game, we find that the strategy with the most occurrences is the "Grim-Trigger." In the Battle of the Sexes game, a cooperative pair that alternates between the two pure-strategy Nash equilibria emerges as the one with the most occurrences. In the Stag-Hunt and Chicken games, the "Win-Stay, Lose-Shift" and "Grim-Trigger" strategies are the ones with the most occurrences. Overall, the pairs that converged quickly ended up at the cooperative outcomes, whereas the ones that were extremely slow to reach convergence ended up at non-cooperative outcomes.

We analyse the evolution of the assortment of encounters through active choice of companions among individuals that interact cooperatively in a situation of mutual benefit. Using a simple mathematical model, we show that mutual benefit can favour the evolution of a preference to interact with individuals that are similar to themselves with respect to an arbitrary tag even when both the preference and the tag depend on two independent and unlinked genes. Two necessary requisites to obtain this result are: (i) a small population or a large subdivided metapulation and (ii) an asymmetry between partners in such a way that one of them (donor) proposes the cooperation and elects the partner, whereas the other (receiver) never rejects the offer. We also show that mutual benefit can be the starting point for the evolution of altruistic behaviours as long as there are preferential interactions. This requires that the tag used in the election of partners is the altruistic or selfish behaviour itself.

Language transfers information on at least three levels; (1) what is said, (2) how it is said (what language is used), and, (3) that it is said (that speaker and listener both possess the ability to use language). The use of language is a form of honest cooperation on two of these levels; not necessarily on what is said, which can be deceitful, but always on how it is said and that it is said. This means that the language encoding and decoding systems had to evolve simultaneously, through mutual fitness benefits. Theoretical problems surrounding the evolution of cooperation disappear if a recognition system is present enabling cooperating individuals to identify each otherif they are equipped with "green beards". Here, I outline how both the biological and cultural aspects of language are bestowed with such recognition systems. The biological capacities required for language signal their presence through speech and understanding. This signaling cannot be invaded by "false green beards" because the traits and the signal of their presence are one and the same. However, the real usefulness of language comes from its potential to convey an infinite number of meanings through the dynamic handling of symbolsthrough language itself. But any specific language also signals its presence to others through usage and understanding. Thus, languages themselves cannot be invaded by "false green beards" because, again, the trait and the signal of its presence are one and the same. These twin green beards, in both the biological and cultural realms, are unique to language.

This paper uses the Price Equation to produce a version of Hamilton's Rule valid for the operation of reciprocal altruism, a mechanism of social evolution that can apply across different species.  This is entirely of historical interest, as it is a snapshot of where many of us were at with regard to social evolution in the 1980s, and is completely pointless now that Frank and Taylor have showed us all how to think about social evolution clearly and simply.  Personally, I often find historical papers interesting even when they have been entirely superseded.  Others may too, so I offer  up this here as the paper itself is not easy to get on the web.

Genetic recombination is a central and repeated topic of study in the evolution of life. However, along with the influence of recombination on evolution, we understand surprisingly little of how selection shapes the nature of recombination. One explanation for recombination is that it allows organisms to escape from perilous situations where they experience very low fitness. As a corollary, it has been suggested that selection should favor recombination at low fitness and not at high fitness (fitness-associated recombination, FAR), and theory suggests that such strategies can indeed be selected. Here we develop models to further investigate the evolution of FAR. Consistent with previous works, we find that FAR can invade and dominate over a strategy of uniform recombination that is independent of fitness. However, our simulation results suggest that extreme FAR strategies, known as group-elitism, are not necessarily superior to other FAR strategies. Moreover, we argue that FAR domination will often occur with a net loss of mean population fitness. Interestingly, this suggests that the strategy of not recombining at high fitness will sometimes be analogous to a defector strategy from the famous ''prisoner's dilemma'' game: a selfish strategy that is selected but leads to a loss of mean fitness for all players. r

Genetic recombination is a central and repeated topic of study in the evolution of life. However, along with the influence of recombination on evolution, we understand surprisingly little of how selection shapes the nature of recombination. One explanation for recombination is that it allows organisms to escape from perilous situations where they experience very low fitness. As a corollary, it has been suggested that selection should favor recombination at low fitness and not at high fitness (fitness-associated recombination, FAR), and theory suggests that such strategies can indeed be selected. Here we develop models to further investigate the evolution of FAR. Consistent with previous works, we find that FAR can invade and dominate over a strategy of uniform recombination that is independent of fitness. However, our simulation results suggest that extreme FAR strategies, known as group-elitism, are not necessarily superior to other FAR strategies. Moreover, we argue that FAR domination will often occur with a net loss of mean population fitness. Interestingly, this suggests that the strategy of not recombining at high fitness will sometimes be analogous to a defector strategy from the famous ''prisoner's dilemma'' game: a selfish strategy that is selected but leads to a loss of mean fitness for all players. r

Genetic recombination is a central and repeated topic of study in the evolution of life. However, along with the influence of recombination on evolution, we understand surprisingly little of how selection shapes the nature of recombination. One explanation for recombination is that it allows organisms to escape from perilous situations where they experience very low fitness. As a corollary, it has been suggested that selection should favor recombination at low fitness and not at high fitness (fitness-associated recombination, FAR), and theory suggests that such strategies can indeed be selected. Here we develop models to further investigate the evolution of FAR. Consistent with previous works, we find that FAR can invade and dominate over a strategy of uniform recombination that is independent of fitness. However, our simulation results suggest that extreme FAR strategies, known as group-elitism, are not necessarily superior to other FAR strategies. Moreover, we argue that FAR domination will often occur with a net loss of mean population fitness. Interestingly, this suggests that the strategy of not recombining at high fitness will sometimes be analogous to a defector strategy from the famous ''prisoner's dilemma'' game: a selfish strategy that is selected but leads to a loss of mean fitness for all players. r

We study the situation of a decision-maker who aims to encourage the players of an evolutionary game theoretic system to follow certain desired behaviours.
To do so, she can interfere in the system to reward her preferred behavioural  patterns.
However, this action requires certain cost (e.g., resource consumption). 
Given this, her main goal is to maintain an efficient trade-off between achieving the desired system status and minimising the total cost spent.
Our  results reveal interesting observations, which suggest that further investigations in the future are required.

In this article, our model consists of two players and two choices for each player. In this model, there is one option for one player in each round called leader. The two players have the same chance to be leader. In this model each two consecutive rounds represent one unit. We consider strategies realized by simple transition rules depending on the previous outcome. We consider homogeneous population of strategy ߗ, and ask for the most favorable adaptation. Any parameter ‫ݏ‬ in ߗ changes according to the adaptive dynamics ‫ݏ‬ሶ ൌ డிሺఆ,ఆ ᇲ ሻ డ௦ where ‫ܨ‬ is the payoff for ߗ-player against ߗ ᇱ ‫ـ‬player and this evaluated at ߗ ᇱ ൌ ߗ.

The principle of cooperation influences our everyday lives. This conflict between individual and collective rationality can be modelled through the use of social dilemmas such as the prisoner's dilemma. Reflecting the reality that real world autonomous agents are not chosen at random to interact, we acknowledge the role some structuring mechanisms can play in increasing cooperation. This paper examines one simple structuring technique which has been shown to increase cooperation among agents. Tagging mechanisms structure a population into subgroups and as a result reflect many aspects which are relevant to the domains of kin selection and trust. We will outline some simulations involving a simple tagging system and outline the main factors which are vital to increasing cooperation.

Philosophers and social scientists have recently turned to game theory and agent-based models to better understand social contract formation. The stag hunt game is an idealization of social contract formation. Using the stag hunt game we attempt to determine what, if any, barrier diversity is to the formation of an efficient social contract. We uncover a deep connection between tolerance, diversity and the social contract. We investigate a simple model in which individuals possess salient traits and behave cooperatively when the difference between their trait and the trait of their counterpart is less than their “tolerance level.” If traits are fixed and correspond to permanent or semi-permanent features of the individual such as religion or race social contract formation is a remote possibility. If traits are malleable, social contract formation is possible but comes at the steep cost of diversity and tolerance – individuals are unwilling to cooperate with those much different from themselves. Yet homogeneity and intolerance are not a long term feature of the population. Over time mutations allow for increasingly tolerant agents to prosper, thereby ushering in trait diversity. In the end, all reap the benefits of cooperation.

When making a mistake, individuals can apologize to secure further cooperation, even if the apology is  costly. Similarly, individuals arrange commitments to guarantee that  an action such as a cooperative one is in the others' best interest, and thus will be carried out to avoid eventual penalties for commitment failure. Hence, both apology and commitment should go side by side in behavioral evolution. Here we provide a computational model showing that apologizing acts are rare in non-committed interactions,  especially whenever cooperation is very costly, and that arranging prior commitments can considerably increase the frequency of such behavior. In addition, we show that in both cases, with or without commitments, apology works only if it is sincere, i.e. costly enough.
Most interestingly, our model predicts that individuals tend to use much costlier  apology in committed relationships than otherwise, because it helps better identify free-riders such as fake committers: `commitments bring about  sincerity'.
Furthermore, we show that this strategy of apology supported by commitments outperforms  the famous existent strategies of the iterated Prisoner's Dilemma.

Abstract We analyse simulations reported in “The co-evolution of individual behaviors and social institutions” by Bowles, Choi & Hopfensitz (2003) in the Journal of Theoretical Biology 223, 135-147 and begin with distinguishing two types of group selection models. The literature does not provide different names for them, but they are shown to be fundamentally different and have quite different empirical implications.

The similarity discrimination effect occurs when a single gene or gene cluster causes its carriers to display both a variable phenotypic trait and a behavioural predisposition to cooperate preferentially with recognisably similar carriers. We distinguish this from the greenbeard effect, in which cooperation evolves through fixed phenotypic tags and genetically linked cooperative behaviour with others displaying the same tag. Our agent-based simulations show that the evolution of cooperation through similarity discrimination, in contrast to the greenbeard effect, does not depend on population viscosity or other restrictive conditions. Similarity discrimination evolves spontaneously in well mixed populations, not only in the Prisoner's Dilemma game but also across a range of different binary-choice strategic interactions, provided that agents can distinguish reliably between similar and dissimilar co-players. (A.M. Colman), lb155@le.ac.uk (L. Browning), bdp5@le.ac.uk (B.D. Pulford).

The similarity discrimination effect occurs when a single gene or gene cluster causes its carriers to display both a variable phenotypic trait and a behavioural predisposition to cooperate preferentially with recognisably similar carriers. We distinguish this from the greenbeard effect, in which cooperation evolves through fixed phenotypic tags and genetically linked cooperative behaviour with others displaying the same tag. Our agent-based simulations show that the evolution of cooperation through similarity discrimination, in contrast to the greenbeard effect, does not depend on population viscosity or other restrictive conditions. Similarity discrimination evolves spontaneously in well mixed populations, not only in the Prisoner's Dilemma game but also across a range of different binary-choice strategic interactions, provided that agents can distinguish reliably between similar and dissimilar co-players. (A.M. Colman), lb155@le.ac.uk (L. Browning), bdp5@le.ac.uk (B.D. Pulford).