BAYESIAN DECISION THEORY, GAME THEORY AND GROUP PROBLEM SOLVING. ESD-TDR-64-603.
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Neurons in a small number of brain structures detect rewards and reward-predicting stimuli and are active during the expectation of predictable food and liquid rewards. These neurons code the reward information according to basic terms of various behavioural theories that seek to explain reward-directed learning, approach behaviour and decision-making. The involved brain structures include groups of dopamine neurons, the striatum including the nucleus accumbens, the orbitofrontal cortex and the amygdala. The reward information is fed to brain structures involved in decision-making and organisation of behaviour, such as the dorsolateral prefrontal cortex and possibly the parietal cortex. The neural coding of basic reward terms derived from formal theories puts the neurophysiological investigation of reward mechanisms on firm conceptual grounds and provides neural correlates for the function of rewards in learning, approach behaviour and decision-making.
Recent theoretical advances have dramatically increased the relevance of game theory for predicting human behavior in interactive situations. By relaxing the classical assumptions of perfect rationality and perfect foresight, we obtain much improved explanations of initial decisions, dynamic patterns of learning and adjustment, and equilibrium steady-state distributions.
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A game theory model of insect population dynamics is proposed. For the case when the population may be in one of two states: when physiological processes are directed to growth and reproduction, and when physiological processes are directed to the development of defense reactions, outbreaks of mass reproduction of insect populations may occur in conditions when population and environment have the "memory", and the state of population and environment depends on their state at the previous time moment. In the framework of the model, the well known effect of insect phase variation during the outbreak of reproduction is explained.
Hospital management can be seen as a game, and doctors, nurses, and health maintenance organizations are its players. The astute hospital manager realizes the interdependence of individual career strategies and the hospital's success, just as players in a game are interdependent on each other. Managers familiar with game theory may successfully transfer that knowledge to the hospital realm. They may recognize patterns and calculate outcomes like chess players, bluff other hospitals into folding services as poker players do, and cooperate with their own team to maximize productivity. Knowledge of game theory may also make the hospital manager's job.
We examine decision making in two-person extensive form game trees using nine treatments that vary matching protocol, payoffs, and payoff information. Our objective is to establish replicable principles of cooperative versus noncooperative behavior that involve the use of signaling, reciprocity, and backward induction strategies, depending on the availability of dominated direct punishing strategies and the probability of repeated interaction with the same partner. Contrary to the predictions of game theory, we find substantial support for cooperation under complete information even in various single-play treatments.
Newlin's [Newlin D.B. Evolutionary game theory of tolerance and sensitization in substance abuse. Paper presented to the Research Society on Alcoholism, Hilton Head, SC, 1998] evolutionary game theory of addictive behavior specifies how evolutionarily stable strategies for survival and reproduction may lead to addiction. The game theory of multiple chemical sensitivity (MCS) assumes that: (1) the MCS patient responds to low-level toxicants as stressors or as direct threats to their survival and reproductive fitness, (2) this activates the cortico-mesolimbic dopamine system, (3) this system is a survival motivation center--not a 'reward center', (4) the subject emits a counter-response that is in the same direction as the naive response to the chemicals, (5) previously neutral stimuli associated with chemicals also trigger conditioned responses that mimic those to the chemicals, (6) these counter-responses further activate the dopaminergic survival motivation system, and (7) this produces a positive feedback loop that leads to strong neural sensitization in these structures and in behavior controlled by this system, despite a small initial response. Psychologically, the MCS patient with a sensitized cortico-mesolimbic dopamine system is behaving as though his/her survival is directly threatened by these chemicals. Non-MCS subjects have counter-responses opposite in direction to those of the chemicals and show tolerance. An autoshaping/sign-tracking model of this game is discussed. This evolutionary game makes several specific, testable predictions about differences between MCS subjects, non-MCS controls, and substance abusers in laboratory experiments, and between sensitized and nonsensitized animals.
Decision making and choices are frequent themes in medical ethics. Game theory is based upon modelled decision making. Game theory, and associated logic traps, may have relevance to the clinical practice of medicine and medical ethics. The "prisoner's dilemma" is one logic trap from game theory in which "rational" decision making on the part of participating individuals can lead to "suboptimal" situations. An example of such a situation involving brain death is presented and discussed from the perspective of the prisoner's dilemma.
This article reviews the more complex aspects of game theory than those presented in a recent HCM article. Following a basic overview of terminology and simplified examples, case studies are presented to show the hospital manager how game theory is a useful modeling strategy for predicting human interactions and the potential outcomes of certain decisions, especially economic ones. Understanding game theory provides the manager with an understanding of basic and advanced strategies that can be utilized to competitive advantage in the health care market (thus giving it applicability at the manager's clinical level of decision making), as well as grasping the "larger picture" of health care decision making at high levels, such as in professional societies and government.
Game theory models of animal contests make many non-mutually exclusive predictions, complicating empirical tests. These predictions regard the relationship between contest parameters and fighting ability, for which body size is usually used as a proxy. However, in many systems, body size may be a limited proxy since multiple traits and contextual factors such as experience influence fighting ability. Using contests between male Cape dwarf chameleons, Bradypodion pumilum, I test alternative game theory models of extended contests. I show how the most likely candidate model can be identified through a process of elimination, based on tests of key predictions. In addition, I present a measure of fighting ability based on multiple traits that allows ability to change as experience changes. In dwarf chameleons, persistence is based on loser thresholds rather than assessment of relative ability, ruling out the sequential assessment model. Winners and losers do not match behaviours in early parts of the contest, arguing against all types of war of attrition models. Although the cumulative assessment model remained as the most likely candidate model, not all specific predictions of this model were upheld.
Economists and psychologists have been testing Nash equilibrium predictions of game theory models of human behavior. In many instances, humans do not conform to the predictions. These results are of great interest to biologists because they also raise questions about well-known ESS models of cooperation. Cooperation in certain one-shot, anonymous interactions, and a willingness to punish others at a net cost to oneself are some of the most intriguing deviations from standard theory. One proposed explanation for these results that is receiving increasing attention invokes the cultural group selection of 'other regarding' social norms. We critically review this explanation. We conclude that experimental results reveal limits in two implicit models of cognitive structure commonly employed by economists and evolutionary biologists.
Decision analysis is an explicit, quantitative and prescriptive means by which the physician can identify optimal clinical strategies under conditions of uncertainty. It is incomplete, however, since it dispenses clinical advice without regard for the fact that the patient--for whatever reason--might choose to reject that advice. Game theory provides a supplementary means to explicate optimal rational strategies in situations where the actual outcome depends on the choices of both the patient and the physician. To determine its potential clinical relevance, we used game theory to reassess a clinical problem which has been used as a textbook exemplar of decision analysis: Should patients with chronic liver failure undergo liver biopsy before being treated? Decision analysis prescribes a pure (deterministic) strategy: the physician should always perform a biopsy. In contrast, given the proper conditions, game theory mandates a mixed (probabilistic) strategy: the physician should (randomly) recommend biopsy to only some fraction of patients, and only some fraction of these should (randomly) accept this advice. Thus, whenever the patient is free to accept or reject the physician's advice, game theory provides a prescriptive decision-making model which is qualitatively and quantitatively different from decision analysis.
The medical consultation is best understood as a two-way social interaction involving interactive decision making. Game theory--a theory based on assumptions of rational choice and focusing on interactive decision making--has the potential to provide models of the consultation that can be used to generate empirically testable predictions about the factors that promote quality of care. Three different game structures--the Prisoner's Dilemma game, the Assurance game, and the Centipede game--all provide insights into the possible underlying dynamics of the doctor-patient interaction. Further empirical work is needed to uncover the underlying game structures that occur most commonly in medical consultations. Game theory has the potential to provide a new conceptual and theoretical basis for future empirical work on the interaction between doctors and their patients.
Rational choice theory enjoys unprecedented popularity and influence in the behavioral and social sciences, but it generates intractable problems when applied to socially interactive decisions. In individual decisions, instrumental rationality is defined in terms of expected utility maximization. This becomes problematic in interactive decisions, when individuals have only partial control over the outcomes, because expected utility maximization is undefined in the absence of assumptions about how the other participants will behave. Game theory therefore incorporates not only rationality but also common knowledge assumptions, enabling players to anticipate their co-players' strategies. Under these assumptions, disparate anomalies emerge. Instrumental rationality, conventionally interpreted, fails to explain intuitively obvious features of human interaction, yields predictions starkly at variance with experimental findings, and breaks down completely in certain cases. In particular, focal point selection in pure coordination games is inexplicable, though it is easily achieved in practice; the intuitively compelling payoff-dominance principle lacks rational justification; rationality in social dilemmas is self-defeating; a key solution concept for cooperative coalition games is frequently inapplicable; and rational choice in certain sequential games generates contradictions. In experiments, human players behave more cooperatively and receive higher payoffs than strict rationality would permit. Orthodox conceptions of rationality are evidently internally deficient and inadequate for explaining human interaction. Psychological game theory, based on nonstandard assumptions, is required to solve these problems, and some suggestions along these lines have already been put forward.
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.
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.
The behavioral dimension matters in Probabilistic Risk Analysis (PRA) since players throughout a system incur costs to increase system reliability interpreted as a public good. Individual strategies at the subsystem level generally conflict with collective desires at the system level. Game theory, the natural tool to analyze individual-collective conflicts that affect risk, is integrated into PRA. Conflicts arise in series, parallel, and summation systems over which player(s) prefer(s) to incur the cost of risk reduction. Frequently, the series, parallel, and summation systems correspond to the four most common games in game theory, i.e., the coordination game, the battle of the sexes and the chicken game, and prisoner's dilemma, respectively.