In the Hamadryas baboon, males are substantially larger than females. A troop of baboons is subdivided into a number of ‘one-male groups’, consisting of one adult male and one or more females with their young. The male prevents any of ‘his’ females from moving too far from him. Kummer (1971) performed the following experiment. Two males, A and B, previously unknown to each other, were placed in a large enclosure. Male A was free to move about the enclosure, but male B was shut in a small cage, from which he could observe A but not interfere. A female, unknown to both males, was then placed in the enclosure. Within 20 minutes male A had persuaded the female to accept his ownership. Male B was then released into the open enclosure. Instead of challenging male A , B avoided any contact, accepting A’s ownership.

Evolution and the Theory of Games

Evolutionary game dynamics is the application of population dynamical methods to game theory. It has been introduced by evolutionary biologists, anticipated in part by classical game theorists. In this survey, we present an overview of the many brands of deterministic dynamical systems motivated by evolutionary game theory, including ordinary differential equations (and, in particular, the replicator equation), differential inclusions (the best response dynamics), difference equations (as, for instance, fictitious play) and reaction-diffusion systems. A recurrent theme (the so-called `folk theorem of evolutionary game theory') is the close connection of the dynamical approach with the Nash equilibrium, but we show that a static, equilibrium-based viewpoint is, on principle, unable to always account for the long-term behaviour of players adjusting their behaviour to maximise their payoff.

https://www.ams.org/bull/2003-40-04/S0273-0979-03-00988-1/S0273-0979-03-00988-1.pdf

Evolutionary Game Dynamics

Economic games are used to investigate the cognitive mechanisms underlying cooperative behaviour, and show that intuition supports cooperation in social dilemmas, whereas reflection can undermine these cooperative impulses. Many people are willing to make sacrifices for the common good, but little is known about the cognitive mechanisms that underlie such cooperative behaviour. In economic experiments subjects often contribute cooperatively against what rational self-interest should dictate. This study uses a series of ten varied experimental designs, including both one-shot and repeated games, to establish whether we are intuitively predisposed to cooperate or to act selfishly. And it seems our gut response is to cooperate — but given more time to think the logic of self-interest undermines collective action and we become less generous. Cooperation is central to human social behaviour1,2,3,4,5,6,7,8,9. However, choosing to cooperate requires individuals to incur a personal cost to benefit others. Here we explore the cognitive basis of cooperative decision-making in humans using a dual-process framework10,11,12,13,14,15,16,17,18. We ask whether people are predisposed towards selfishness, behaving cooperatively only through active self-control; or whether they are intuitively cooperative, with reflection and prospective reasoning favouring ‘rational’ self-interest. To investigate this issue, we perform ten studies using economic games. We find that across a range of experimental designs, subjects who reach their decisions more quickly are more cooperative. Furthermore, forcing subjects to decide quickly increases contributions, whereas instructing them to reflect and forcing them to decide slowly decreases contributions. Finally, an induction that primes subjects to trust their intuitions increases contributions compared with an induction that promotes greater reflection. To explain these results, we propose that cooperation is intuitive because cooperative heuristics are developed in daily life where cooperation is typically advantageous. We then validate predictions generated by this proposed mechanism. Our results provide convergent evidence that intuition supports cooperation in social dilemmas, and that reflection can undermine these cooperative impulses.

/pdf/spontaneous-giving-and-calculated-greed-10q2b8pxf2.pdf

Spontaneous giving and calculated greed

We develop a model of friendship formation that sheds light on segregation patterns observed in social and economic networks Individuals have types and see type-dependent benefits from friendships We examine the properties of a steady-state equilibrium of a matching process of friendship formation We use the model to understand three empirical patterns of friendship formation: (i) larger groups tend to form more same-type ties and fewer other-type ties than small groups, (ii) larger groups form more ties per capita, and (iii) all groups are biased towards same-type relative to demographics, with the most extreme bias coming from middle-sized groups We show how these empirical observations can be generated by biases in preferences and biases in meetings We also illustrate some welfare implications of the model

/pdf/an-economic-model-of-friendship-homophily-minorities-and-wpbte861in.pdf

An Economic Model of Friendship: Homophily, Minorities and Segregation

A first course in stochastic processes

https://kops.uni-konstanz.de/bitstream/handle/123456789/11952/50_08_06_TWI_RPS_Alos_Ferrer_Netzer.pdf;sequence=1

The Logit-Response Dynamics

From dual processes to multiple selves: implications for economic behavior

In a (generalized) symmetric aggregative game, payoffs depend only on individual strategy and an aggregate of all strategies. Players behaving as if they were negligible would optimize taking the aggregate as given. We provide evolutionary and dynamic foundations for such behavior when the game satisfies supermodularity conditions. The results obtained are also useful to characterize evolutionarily stable strategies in a finite population.

/pdf/the-evolutionary-stability-of-perfectly-competitive-behavior-4v5zitvx3h.pdf

The Evolutionary Stability of Perfectly Competitive Behavior

We study the effects of ego depletion, a manipulation which consumes self-control resources, on social preferences in a dictator game. Depleted dictators give considerably less than non-depleted dictators and hence exhibit strong preferences for selfish allocation. In contrast to earlier studies, participants were explicitly paid for completing the egodepletion task (with either a flat rate or strictly performance-based payment). We studied the dynamics of decisions by repeating the dictator game 12 times (anonymously). Depleted dictators start with much lower offers than non-depleted ones, but, strikingly, offers decrease in time for both groups, and more rapidly so for non-depleted dictators. We conclude that, while depleted dictators neglect fairness motives from the very first decision on, non-depleted dictators initially resist the tendency to act selfishly, but eventually become depleted or learn to act selfishly. Hence, prosocial behavior may be short-lived, and ego depletion uncovers the default tendencies for selfishness earlier.

/pdf/money-depletion-and-prosociality-in-the-dictator-game-2nuqo4je9y.pdf

Money, depletion, and prosociality in the dictator game

We present a simple model for decision making under uncertainty building on dual-process theories from psychology, and use it to illustrate a possible component of intuitive decision making of particular relevance for managerial settings. Decisions are the result of the interaction between two decision processes. The first one captures optimization based on Bayesian updating of beliefs. The second corresponds to a form of reinforcement learning capturing the tendency to rely on past performance. The model predicts that (i) in the case of conflict between the two processes, correct responses are associated with longer response times, but (ii) if both processes are aligned, errors are slower. Furthermore, (iii) response times in the case of conflict are longer than in the case of alignment. We confirm the predictions of the model in an experiment using a paradigm where an associative win-stay, lose-shift process conflicted with rational belief updating.

Carlos Alós-Ferrer

Papers

The Logit-Response Dynamics

From dual processes to multiple selves: implications for economic behavior

The Evolutionary Stability of Perfectly Competitive Behavior

Money, depletion, and prosociality in the dictator game

Fast or Rational? A Response-Times Study of Bayesian Updating