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To each genotype a separate strategy--a dynamic game theory model of a general diploid system.

A dynamic game theory model is presented for a diploid system in which each genotype corresponds to a different strategy. The population mates randomly and the strategy, which is determined by a single locus, is expressed only in the male. A general analytic solution for any number of alleles does not appear to be possible, but the cases of two and three alleles are treated in detail. A stability analysis applicable to any number of alleles is presented, so that any equilibria located by numerical methods can be checked for local stability. Computer programs for doing all of these calculations are available from the author.

Alleles

Game theory and the evolution of behaviour.

How far can game theory account for the evolution of contest behaviour in animals? The first qualitative prediction of the theory was that symmetric contests in which escalation is expensive should lead to mixed strategies. As yet it is hard to say how far this is borne out, because of the difficulty of distinguishing a 'mixed evolutionarily stable strategy' maintained by frequency-dependent selection from a 'pure conditional strategy'; the distinction is discussed in relation to several field studies. The second prediction was that if a contest is asymmetric (e.g. in ownership) then the asymmetry will be used as a conventional cue to settle it. This prediction has been well supported by observation. A third important issue is whether or not information about intentions is exchanged during contests. The significance of 'assessment' strategies is discussed.

Aggression

A simple model of host-parasite evolutionary relationships. Parasitism: compromise or conflict?

The evolutionary biology of host-parasite relationships are considered here using a simple game-theory model in which hosts play against parasite and vice versa. In this model, the players can choose between two strategies (aggressive or not aggressive) and the utility of the game is envisaged in terms of fitness and selective costs. The game solutions suggest that the two types of confrontation are encountered in symbiotic relationships and thus constitute two Evolutionary Stable Strategies (ESS). These observations lead us to discuss: (i) the status of different kinds of symbiotic relationships (i.e. parasitoidism; parasitism, commensalism and mutualism) related to selective costs and (ii) the position of coevolution in this game theory context.

Animals

Distinguishing mechanisms for the evolution of co-operation.

The existence of co-operation between species has been cast as a problem to the selfish-gene view of evolution: why does co-operation persist, when it would seem that individual selection should favor the unco-operative individual who exploits the co-operative tendencies of its partner and gives nothing in return? The recent literature has emphasized one type of model as underlying the evolution and stability of interspecific co-operation, which we term the "partner-fidelity" model, and which is typified by the game theory model known as the iterated Prisoner's Dilemma game. Under this mechanism, individuals are associated with the same partner(s) during an indefinite sequence of interactions. Individuals who at any time fail to co-operate with their partner can be penalized by those same partners in subsequent trials, hence the co-operation can be evolutionarily stable. Many examples of biological co-operation that have been offered appear to conform to this model. However, a few examples appear instead to fit a different and unrecognized mechanism, termed "partner-choice". Under partner-choice, individuals are associated for just one interaction, but an asymmetry enables one member to differentially reward co-operative vs. unco-operative partners in advance of any possible exploitation. Possible examples of co-operation maintained through partner-choice mechanisms are provided by the yucca/yucca moth system and the fig/fig wasp system.

Animals

Stress-driven strategic games in cancer.

Tumor cells face chronic genotoxic, metabolic, hypoxic, and immune stress that shapes their evolution. While stress-response molecular pathways are well characterized, cancer biology lacks a predictive framework for how cells select among alternative adaptive strategies and how these selections interact to produce tumor-level behavior. We propose that evolutionary game theory, previously applied to cooperation in cancer, should be extended to position stress adaptation itself as the organizing principle of tumor evolution. In this framework, stress-adaptive strategies constitute frequency-dependent games whose payoffs depend on population composition. We introduce a three-level distinction between cell states (transcriptional snapshots), game states (local configurations of stress and neighbor composition that define the active payoff structure), and cell strategies (conditional behavioral policies mapping game states to fitness-relevant outputs). This perspective explains the maintenance of intratumor heterogeneity through frequency-dependent selection, the reversibility of resistance through bet-hedging dynamics, and therapy resistance as an equilibrium outcome rather than genetic inevitability. Integrating insights from single-cell genomics, spatial profiling, and lineage tracing, we outline testable predictions and experimental approaches for measuring payoff structures. Therapeutically, the framework suggests exploiting adaptive trade-offs, restricting phenotypic plasticity, and reshaping competitive landscapes. Re-framing cancer as an evolving game of stress adaptation provides a unifying structure for predictive oncology.

Animals

Can road traffic law enforcement permanently reduce the number of accidents?

In this paper it is argued that conventional analyses of road user adaptation to traffic law enforcement, based on parametric rational-choice theory, are flawed. Such analyses only consider road-user actions as a response to enforcement level and penalty size and do not simultaneously consider enforcement as a response to road-user behaviour. If each party is considered a rational agent who adapts to the other's behaviour, the proper way to analyze the outcomes is by the way of game theory. A game-theoretic model is presented and the main implications are: (i) most attempts at enforcing road traffic legislation will not have any lasting effects, either on road-user behaviour or on accidents; (ii) imposing stricter penalties (in the form of higher fines or longer prison sentences) will not affect road-user behaviour; (iii) imposing stricter penalties will reduce the level of enforcement; (iv) implementing automatic traffic surveillance techniques and/or allocating enforcement resources according to a chance mechanism, and not according to police estimates of violation probability, can make enforcement effects last, but both alternatives are difficult to implement. Relevant empirical studies are reviewed, and they seem to support the conclusions arrived at by the game-theoretic model.

Accidents, Traffic

Sociobiology and the structural stability of behavior patterns.

A structural stability approach to population-genetic systems and to dynamic evolutionary games is attempted in order to examine the theoretical significance of sociobiological selection models. A criterion of weak selection is derived that is not restricted to differential reproduction in polymorphic systems but describes possible directions of evolutionary change in time scales governed by genetic mutation rates. The criterion applies to the problems of how the initial mutational basis of an adaptive trait may be established and how this may happen, for analogous traits, independently in different species. Two basic sociobiological concepts are reconsidered with reference to the criterion. It is shown that W. D. Hamilton's condition of increases in inclusive fitness due to altruistic interactions among kin expresses the structural instability of populations against the evolution of altruistic behavior. Using the dynamic approach to evolutionary game theory, it is demonstrated that if a behavioral phenotype is an evolutionarily stable strategy, it is structurally stable against perturbations of the fitness payoffs, provided selection is weak. These results are applied to material problems of the evolution of animal social behavior.

Animals

Gregory Bateson and the mathematicians: from interdisciplinary interaction to societal functions.

An instance of fruitful cross-disciplinary contacts is examined in detail. The ideas involved include (1) the double-blind hypothesis for schizophrenia, (2) the critique of game theory from the viewpoint of anthropology and psychiatry, and (3) the application of concepts of communication theory and theory of logical types to an interpretation of psychoanalytic practice. The protagonists of the interchange are Gregory Bateson and the two mathematicians Norbert Wiener and John von Neumann; the date, March 1946. This interchange and its sequels are described. While the interchanges between Bateson and Wiener were fruitful, those between Bateson and von Neumann were much less so. The latter two held conflicting premises concerning what is significant in science; Bateson's and Wiener's were compatible. In 1946, Wiener suggested that information and communication might be appropriate central concepts for psychoanalytic theory--a vague general idea which Bateson (with Ruesch) related to contemporary clinical practice. For Bateson, Wiener, and von Neumann, the cross-disciplinary interactions foreshadowed a shift in activities and new roles in society, to which the post World War II period was conducive. Von Neumann became a high-level government advisor; Wiener, an interpreter of science and technology for the general public; and Bateson a counter-culture figure.

Anthropology

Sex ratio polymorphism: the impact of mutation and drift on evolution.

This paper addresses the question, which sex ratio will evolve in a population that is subject to mutation and drift. The problem is analyzed using a simulation model as well as analytical methods. A detailed simulation model for the evolution of a population's allele distribution shows that for the sex ratio game a wide spectrum of different population states may evolve from on the one hand a monomorphic state with one predominant allele and with all other alleles suppressed by the forces of selection, to on the other hand a polymorphism determined by recurrent mutations. Which of these states will evolve depends on the population size, the mating system and the rate of mutations. For the sex ratio game the evolutionary stable strategy (ESS), as defined by evolutionary game theory, can only predict the population sex ratio but not the underlying stable population state. A comparison of different approaches to the problem shows that false predictions of the stable population states might result from two simplifying assumptions that are fairly common in evolutionary biology: a) it is assumed that mutations are rare events and there is never more than one mutant gene present in a population at any one time; b) a deterministic relationship is assumed between the fitness assigned to an individual's strategy and the individual's contribution to the gene pool of future generations.

Animals

Brinkmanship in intragenomic conflict.

When the Darwinian interests of genes in the genome collide, intragenomic conflicts evolve. Recent advances in social evolution predict that intragenomic conflicts shape diverse phenotypes. However, principles governing which side wins remain unresolved. Here, we use game theory to predict that power asymmetries arise from differences in appetite for risk between rival genes in 'wars of nerve'. We focus on 'genomic imprinting': differing expression between alleles inherited from mothers and fathers. Escalating conflict is commonly believed to risk damaging the whole organism. We show that genes can exploit risk strategically: genes prepared to take greater risks with the body's vulnerability to disorders and mortality gain coercive advantages, deterring countermoves. Kin selection generates differences in appetite for risk: for instance, if harm to the body frees resources for maternal siblings, genes from mothers have less to lose from gambling with the current body than do genes from fathers. Seemingly maladaptive developmental risks can be adaptively useful for higher-nerve genes, much as political states manipulate risk to coerce rivals. Our results suggest a determinant of power alongside the 'loudest voice prevails' principle, and call for empirical investigation of the extent and means by which risks of imprinting-related disorders are amplified by intragenomic brinkmanship.

Genomic Imprinting

Gametocyte sex ratios as indirect measures of outcrossing rates in malaria.

The frequency of recombination between unlike genotypes is central to understanding the generation of genetic diversity in natural populations of malaria. Here we suggest a way of investigating the problem which could complement conventional biochemical approaches to the population genetics of malaria. Sex allocation theory is one of the most successful areas of evolutionary biology. A well-supported prediction is that progressively less female-biased sex ratios are favoured with more outcrossing; equal numbers of males and females being evolutionarily stable in randomly mating outbred populations. We present a simple game theory model to support the idea that outcrossing rates in malaria will be correlated with the sex ratio of gametocytes in the peripheral blood of vertebrate hosts. Blood films from epidemiological surveys and culture-adapted isolates from Madang Province, Papua New Guinea, were used to estimate average gametocyte sex ratio of Plasmodium falciparum in the area. The geometric mean proportion of males in the population was 0.18 (95% confidence limits: 0.15-0.22). From our model, we estimate that, on average, 36% of zygotes are the result of outcrossing. This estimate assumes that most microgametes released following exflagellation are capable of fertilization. If, on average, fewer than about 70% of microgametes are capable of fertilization (as is the case in at least one other species of Plasmodium), the observed sex ratio would be consistent with between zero and 36% of zygotes being the result of outcrossing. These estimates suggest that there is usually a numerically dominant genotype in the gametocyte population in a blood meal, and that a considerable amount of selfing is occurring in P. falciparum populations in the Madang region, even though it is an area of intense year-round transmission.

Animals

Utilization of board gaming for conceptual models of nursing.

Gaming can be an effective teaching strategy for reinforcing and motivating students to learn. Development of the game discussed in this article is not intended to replace classroom instruction. Instead, it is intended to augment course content. Board gaming can make learning a pleasant experience. It provides students and educators an opportunity to interact in an informal atmosphere and provides enjoyment, while at the same time may promote learning. Therefore, educators should consider further development of games for use with students in nursing education.

Education, Nursing