Never change a winning team: The effect of substitutions on success in football tournaments

We identify a strong and significant negative effect of substitutions in (irrelevant) early games in worldcup and olympic football tournaments on performance in later rounds. We argue that this effect is due to the psychological consequences of such a decision and evaluate alternative possible explanations.Economics (Jel: A)

A MODEL OF IMMIGRATION, INTEGRATION AND CULTURAL TRANSMISSION OF SOCIAL NORMS

I present and study an evolutionary model of immigration and culturaltransmission of social norms in a set-up where agents are repeatedly matchedto play a one-shot interaction prisoner´s dilemma. Matching can be non-randomdue to limited integration (or population viscosity). The latter refers to atendency of individuals to have a higher rate of interaction with individuals oftheir type than with similar numbers of other agents. I derive a culturaltransmission mechanism in order to examine the influence of viscosity and ofother institutional characteristics of society on the evolutionary selection of prosocialnorms. The main findings are that strict norms, sustained by stronginternal punishment, need either viscosity or strong institutional pressures topersist, while norms of intermediate strength persist under a variety ofinstitutional characteristics. Endogenizing norm strength allows to identify twoscenarios in which pro-social norms survive: One of rigidity in whichseparation (high viscosity) leads to monomorphic equilibria with strict normsfor cooperation. And one of integration (low viscosity) where intermediatenorms persist in polymorphic equilibria. Furthermore, with endogenous norms,viscosity and cooperation are not linked in a monotone way.Cultural Evolution, Game Theory, Social Norms, Cooperation, Population Viscosity.

Learning by (limited) forward looking players

We present a model of adaptive economic agents that are k periods forward looking. Agents in our model are randomly matched to interact in finitely repeated games. They form beliefs by relying on their past experience in the same situation (after the same recent history) and then best respond to these beliefs looking k periods ahead. We establish almost sure convergence of our stochastic process and characterize absorbing sets. These can be very different from the predictions in both the fully rational model and the adaptive, but myopic case. In particular we find that also Non-Nash outcomes can be sustained almost all the time whenever they are individually rational and satisfy an efficiency condition. We then characterize stochastically stable states in 2×2 games and show that under certain conditions the efficient action in Prisoner''s Dilemma games and Coordination games can be singled out as uniquely stochastically stable. We show that our results are consistent with typical patterns observed in experiments on finitely repeated Prisoner''s Dilemma games. Finally, if populations are composed of some myopic and some forward looking agents parameter constellations exists such that either might obtain higher average payoffs.Economics (Jel: A)

Strategic behavior in repeated voluntary contribution experiments

We conduct a repeated VCM (voluntary contribution mechanism) experiment using thestrategy method. We compare a partner and a stranger design and find that participantsin the partner treatment provide (i) higher initial contributions, (ii) higher contributionson average over all periods, and (iii) contributions that do not vary more strongly withpast contributions than participants in the stranger treatment. We conclude from ourevidence that strategic motives can account for a large share of the treatment differencestypically observed in this literature.public economics ;

GROUP SELECTION WITH IMPERFECT SEPARATION - AN EXPERIMENT

We experimentally investigate the effect of imperfect separation of groups on group selection and cooperation in a standard prisoner¿s dilemma environment. Subjects can repeatedly choose between two groups, where in one of them an institutionalized norm fosters cooperation. The degree of separation of the two groups is varied between treatments. We find that both, the share of participants that choose into the group where the norm is implemented and the share of participants that cooperate, rise monotonously with the degree of group separation. Furthermore with higher group separation significantly more subjects support the enforcement of the norm.Experiments, Cooperation, Group Selection, Social Norms, Population Viscosity.

Let me sleep on it: Delay reduces rejection rates in Ultimatum Games

We show that delaying acceptance decisions in the Ultimatum Game drastically increases acceptance rates of low offers. While in standard treatments without delay less than 20% of low offers are accepted, these numbers increase to around 65-75% as we delay the acceptance decisions by around 10 minutes. Our findings provide precise evidence for familiar notions such as ''sleeping on it'' and show that there may be a good reason why public administrations often communicate bad news on Friday afternoons. They shed new light on recent evidence in Neuroscience on brain activation after receiving bad news and raise questions about the extent to which decisions reveal the preferences of a decision-maker.microeconomics ;

Learn Without Counterfactuals

In this paper we study learning procedures when counterfactuals (payo s of not-chosen actions) are not observed. The decision maker reasons in two steps: First, she updates her propensities for each action after every payo experience, where propensity is de ned as how much she prefers each action. Then, she transforms these propensities into choice probabilities. We introduce natural axioms in the way propensities are updated and the way propensities are translated into choice, and study the decision marker's behavior when such axioms are in place.Adaptive Learning; Counterfactuals; Partial Information; Reinforcement Learning

COOPERATION IN VISCOUS POPULATIONS - EXPERIMENTAL EVIDENCE

We experimentally investigate the effect of population viscosity (an increased probability to interact with others of one's type or group) on cooperation in a standard prisoner's dilemma environment. Subjects can repeatedly choose between two groups that differ in the defector gain in the associated prisoner's dilemma. Choosing into the group with the smaller defector-gain can signal one's willingness to cooperate. The degree of viscosity is varied across treatments. We find that viscosity produces an endogenous sorting of cooperators and defectors and persistently high rates ofcooperation. Higher viscosity leads to a sharp increase in overall cooperation rates and in addition positively affects the subjects' intrinsic willingness to cooperate.Experiments, Cooperation, Group Selection, Norms, Population

Cooperation through Imitation and Exclusion in Networks

We develop a simple model to study the coevolution of interaction structures and action choices in Prisoners’ Dilemma games. Agents are boundedly rational and choose both actions and interaction partners via payoff-based imitation. The dynamics of imitation and exclusion yields polymorphic outcomes under a wide range of parameters. Depending on the parameters of the model two scenarios can arise. Either there is “full separation” of defectors and cooperators, i.e. they are found in two different, disconnected components. Or there is “marginalization” of defectors, i.e. connected networks emerge with a center of cooperators and a periphery of defectors. Simulations confirm our analytical results and show that the share of cooperators increases with the speed at which the network evolves, increases with the radius of interaction and decreases with the radius of information of agents.Game Theory, Cooperation, Imitation Learning, Network Formation

An Experiment on Learning in a Multiple Games Environment

We study experimentally how players learn to make decisions if they face many different (normal-form) games. Games are generated randomly from a uniform distribution in each of 100 rounds. We find that agents do extrapolate between games but learn to play strategically equivalent games in the same way. If either there are few games or if explicit information about the opponent''s behavior is provided (or both) convergence to the unique Nash equilibrium generally occurs. Otherwise this is not the case and play converges to a distribution of actions which is Non-Nash. Action choices, though, that cannot be explained by theoretical models of either belief-bundling or action bundling are never observed. Estimating different learning models we find that Nash choices are best explained by finer categorizations than Non-Nash choices. Furthermore participants scoring better in the "Cognitive Reflection Test" choose Nash actions more often than other participants.microeconomics ;