Beneficial laggards: multilevel selection, cooperative polymorphism and division of labour in threshold public good games

<p>Abstract</p> <p>Background</p> <p>The origin and stability of cooperation is a hot topic in social and behavioural sciences. A complicated conundrum exists as defectors have an advantage over cooperators, whenever cooperation is costly so consequently, not cooperating pays off. In addition, the discovery that humans and some animal populations, such as lions, are polymorphic, where cooperators and defectors stably live together -- while defectors are not being punished--, is even more puzzling. Here we offer a novel explanation based on a Threshold Public Good Game (PGG) that includes the interaction of individual and group level selection, where individuals can contribute to multiple collective actions, in our model group hunting and group defense.</p> <p>Results</p> <p>Our results show that there are polymorphic equilibria in Threshold PGGs; that multi-level selection does not select for the most cooperators per group but selects those close to the optimum number of cooperators (in terms of the Threshold PGG). In particular for medium cost values division of labour evolves within the group with regard to the two types of cooperative actions (hunting vs. defense). Moreover we show evidence that spatial population structure promotes cooperation in multiple PGGs. We also demonstrate that these results apply for a wide range of non-linear benefit function types.</p> <p>Conclusions</p> <p>We demonstrate that cooperation can be stable in Threshold PGG, even when the proportion of so called free riders is high in the population. A fundamentally new mechanism is proposed how laggards, individuals that have a high tendency to defect during one specific group action can actually contribute to the fitness of the group, by playing part in an optimal resource allocation in Threshold Public Good Games. In general, our results show that acknowledging a multilevel selection process will open up novel explanations for collective actions.</p

One problem, too many solutions: How costly is honest signalling of need?

Our results show that costly signalling theory cannot predict a unique equilibrium cost in signalling games of parent-offspring conflicts if signal cost depends on offspring condition. It follows, contrary to previous claims, that the existence of parent-offspring conflict does not imply costly equilibrium signals

Language Evolution

How did language develop and evolve? Here, linguists, cognitive scientists, behavioural ecologists, and theoretical biologists all offer their disparate views on this emerging fiel

Kooperáció és kommunikáció az állatvilágban: játékelméleti vizsgálatok = Cooperation and communication in biology: game theoretical studies

Pályázatunk elsősorban a kooperáció eredetének számos aspektusát, továbbá a komunikációs rendszerek őszinteségét fenntartó mechanizmusok tanulmányozta. Az elméleti munkák mellett e témakörben humán és állatkísérleteket is elindítottunk. Rámutattunk az olcsó vagy költségmentes kommunikáció őszinteségét fenntartó ökológiai tényezőkre. Megmutattuk például, hogy az emberi kooperáció és az őszinte kommunikáció evolúciója szoros kapcsolatban lehet, illetve állati társadalmakban a kommunikácó őszinteségét a kompetíció erőssége is befolyásolhatja. Vizsgáltuk az ember és a kutya kooperációjának kommunikációs sajátságait. Megmutattuk, hogy a préda-perdátor vagy gazda-parazita kölcsönhatások ismerete szükséges számos kooperatív viselkedés evolúciójának értelmezéséhez. Például a predációs nyomás okozhatja a prédák altruista viselkedését, vagy a kasztrációs parazitát éppen a mutualista társ jelenléte szabályozza. Számos tanulmányban az egyedek térbeli elhelyezkedésének és korlátozott mozgásának a kooperáció evolúciójára kifejtett hatását vizsgáltuk. Több olyan munkánk is született, ahol a humán kommunikáció illetve kooperáció sajátságait a többszintű szelekciós modellek segítségével értelmeztük. Sikerült kiépítsünk egy számítógépes labort, mellyel a jövőben s humán etológiai kísérleteket tudunk végezni. A kutatás legfontosabb eszközének számító evolúciós játékelméletben számos alapkutatás jellegű eredményünk is született, a sztochasztikus elmélet fejlesztésétől a többfajos elméletig. | Our project mainly focused on several aspects of the evolution of cooperation and of the mechanisms maintaining honesty in communicating systems. Beside theoretical works we started animal and human experiments as well. We reveal ecological backgrounds maintaining honesty of cheap or costless communication in numerous systems. It is shown for example that the origin of human cooperation and reliable information processing can be in close connection to each other, and that strength of competition modifies the level of honesty in animal communities. We studied the characteristics of communication in the case of human-dog cooperation. We have shown that characteristics of predator-prey or host-parasite interactions are required to explain evolution of cooperative behaviour in numerous cases. For example, predation load can cause altruistic predator defence among preys, or a mutualistic competitor can control castrating parasites. Several papers focused on the spatial aspects and limited migration of individuals on the evolution of cooperation. Other works emphasized that characteristics of human cooperation can be explained by multilevel selection. We set up a computer lab, which could be a basis of a series of human behavior experiment in the near future. We have significant purely theoretical results in the field of our primary mathematical method, that is of evolutionary game theory; from the development of stochastic theory to the multi-species theory

Does the handicap principle explain the evolution of dimorphic ornaments?

Clifton et al. (2016) in recent paper argue that the handicap principle can explanation the evolution of bimodal ornament distributions. Számadó and Penn (in preparation, Does the handicap) provide a critique of this claim. They point out that the results of the Clifton et al. (2016) depends on a specific assumption about the benefits of ornamentation, namely the fact that this benefit function has an inflection point at the average ornament size. Thus, the handicap principle is neither necessary nor sufficient to explain bimodal ornament distributions

Deception Undermines the Stability of Cooperation in Games of Indirect Reciprocity

Indirect reciprocity is often claimed as one of the key mechanisms of human cooperation. It works only if there is a reputational score keeping and each individual can inform with high probability which other individuals were good or bad in the previous round. Gossip is often proposed as a mechanism that can maintain such coherence of reputations in the face of errors of transmission. Random errors, however, are not the only source of uncertainty in such situations. The possibility of deceptive communication, where the signallers aim to misinform the receiver cannot be excluded. While there is plenty of evidence for deceptive communication in humans the possibility of deception is not yet incorporated into models of indirect reciprocity. Here we show that when deceptive strategies are allowed in the population it will cause the collapse of the coherence of reputations and thus in turn it results the collapse of cooperation. This collapse is independent of the norms and the cost and benefit values. It is due to the fact that there is no selection for honest communication in the framework of indirect reciprocity. It follows that indirect reciprocity can be only proposed plausibly as a mechanism of human cooperation if additional mechanisms are specified in the model that maintains honesty

Scarce and directly beneficial reputations support cooperation

A human solution to the problem of cooperation is the maintenance of informal reputation hierarchies. Reputational information contributes to cooperation by providing guidelines about previous group-beneficial or free-rider behaviour in social dilemma interactions. How reputation information could be credible, however, remains a puzzle. We test two potential safeguards to ensure credibility: (i) reputation is a scarce resource and (ii) it is not earned for direct benefits. We test these solutions in a laboratory experiment in which participants played two-person Prisoner’s Dilemma games without partner selection, could observe some other interactions, and could communicate reputational information about possible opponents to each other. Reputational information clearly influenced cooperation decisions. Although cooperation was not sustained at a high level in any of the conditions, the possibility of exchanging third-party information was able to temporarily increase the level of strategic cooperation when reputation was a scarce resource and reputational scores were directly translated into monetary benefits. We found that competition for monetary rewards or unrestricted non-monetary reputational rewards helped the reputation system to be informative. Finally, we found that high reputational scores are reinforced further as they are rewarded with positive messages, and positive gossip was leading to higher reputations

One problem, too many solutions: How costly is honest signalling of need?

The “cost of begging” is a prominent prediction of costly signalling theory, suggesting that offspring begging has to be costly in order to be honest. Seminal signalling models predict that there is a unique equilibrium cost function for the offspring that results in honest signalling and this cost function must be proportional to parent’s fitness loss. This prediction is only valid if signal cost and offspring condition is assumed to be independent. Here we generalize these models by allowing signal cost to depend on offspring condition. We demonstrate in the generalized model that any signal cost proportional to the fitness gain of the offspring also results in honest signalling. Moreover, we show that any linear combination of the two cost functions (one proportional to parent’s fitness loss, as in previous models, the other to offspring’s fitness gain) also leads to honest signalling in equilibrium, yielding infinitely many solutions. Furthermore, we demonstrate that there exist linear combinations such that the equilibrium cost of signals is negative and the signal is honest. Our results show that costly signalling theory cannot predict a unique equilibrium cost in signalling games of parent-offspring conflicts if signal cost depends on offspring condition. It follows, contrary to previous claims, that the existence of parent-offspring conflict does not imply costly equilibrium signals. As an important consequence, it is meaningless to measure the “cost of begging” as long as the dependence of signal cost on offspring condition is unknown. Any measured equilibrium cost in case of condition-dependent signal cost has to be compared both to the parent’s fitness loss and to the offspring’s fitness gain in order to provide meaningful interpretation