On the Evolution of Preferences

A common feature of the literature on the evolution of preferences is that evolution favors nonmaterialistic preferences only if preference types are observable at least to some degree. We argue that this result is due to the assumption that in each state of the evolutionary dynamics some Bayesian Nash equilibrium is played. We show that under unobservability of preference types, conditional on selecting some self-confirming equilibrium as a rule for mapping preference into behavior, non-selfish preferences may be evolutionarily successful.evolution of preferences, altruism, learning, self-confirming equilibrium

The Evolutionary Stability of Optimism, Pessimism and Complete Ignorance

We provide an evolutionary foundation to evidence that in some situations humans maintain optimistic or pessimistic attitudes towards uncertainty and are ignorant to relevant aspects of the environment. Players in strategic games face Knightian uncertainty about opponents’ actions and maximize individually their Choquet expected utility. Our Choquet expected utility model allows for both an optimistic or pessimistic attitude towards uncertainty as well as ignorance to strategic dependencies. An optimist (resp. pessimist) overweights good (resp. bad) outcomes. A complete ignorant never reacts to opponents’ change of actions. With qualifications we show that optimistic (resp. pessimistic) complete ignorance is evolutionary stable / yields a strategic advantage in submodular (resp. supermodular) games with aggregate externalities. Moreover, this evolutionary stable preference leads to Walrasian behavior in those classes of games

Reciprocity - an indirect evolutionary analysis

This paper investigates strategic interaction between rational agents whose preferences evolve over time. Players face a pecuniary �game of life� comprising the ultimatum game and the dictator game. Utility may but need not be attached to the reciprocation of fair and unfair play by the opponent and equitable payoff distributions as proposed by Falk and Fischbacher (2001). Evolutionary fitness is determined solely by material success � regardless of the motives for its achievement. Agents cannot explicitly condition the social component of their preferences on whether they face the ultimatum or dictator game. Under these conditions, agents develop a strong preference for reciprocation but little interest in an equitable distribution as such. This corresponds to equitable ultimatum offers but full surplus appropriation by dictators. Adding an exogenous constraint on the possible divergence between preference for reciprocation and for an equitable distribution either makes ultimatum divisions asymmetric or dictators become generous depending on the relative frequency of ultimatum and dictator interaction.

Trust, Introspection, and Market Participation: an Evolutionary Approach

We build a model where introspection matters - i.e., people rationally form expectations about others using the lens of their own attitudes. Since trustworthy individuals are more "optimistic" about people than opportunists, they are less afraid to engage in market-based exchanges, where they may be vulnerable to opportunistic behavior. Within this context, we use an indirect evolutionary approach to endogenize preferences for trustworthiness. In some cases, the material rewards from greater market participation may outweigh the material disadvantages from foregoing lucrative expropriation opportunities. This implies that trustworthiness may be evolutionary stable in the long-term. Although stricter enforcement (that limits the scope for opportunistic behavior) does in some cases favor preferences for trustworthy behavior (crowding in) we show that the opposite (crowding out) may also occur. Our findings are consistent with recent empirical evidence.Endogenous Preferences; Trust; Introspection; Institutions; Enforcement; Crowding Out

Vengefulness Evolves in Small Groups

We discuss how small group interactions overcome evolutionary problems that might otherwise erode vengefulness as a preference trait. The basic viability problem is that the fitness benefits of vengeance often do not cover its personal cost. Even when a sufficiently high level of vengefulness brings increased fitness, at lower levels, vengefulness has a negative fitness gradient. This leads to the threshold problem: how can vengefulness become established in the first place? If it somehow becomes established at a high level, vengefulness creates an attractive niche for cheap imitators, those who look like highly vengeful types but do not bear the costs. This is the mimicry problem, and unchecked it could eliminate vengeful traits. We show how within-group social norms can solve these problems even when encounters with outsiders are also important.

Equilibrium Vengeance

This paper introduces two ideas, emotional state dependent utility components (ESDUCs), and evolutionary perfect Bayesian equilibrium (EPBE). Using a simple extensive form game, we illustrate the efficiency-enhancing role of a powerful ESDUC, the vengeance motive. Incorporating behavioral noise and observational noise leads to a range of (short run) Perfect Bayesian equilibria (PBE) involving both vengeful and non-vengeful types. We then derive two (long run) EPBE, one where both types survive and reap mutual gains, and a second where only the non-vengeful type survives and there are no mutual gains.negative reciprocity, perfect Bayesian equilibrium, evolutionary perfect Bayesian equilibrium, emotional state dependent utility

Equilibrium Vengeance

The efficiency-enhancing role of the vengeance motive is illustrated in a simple social dilemma game in extensive form. Incorporating behavioral noise and observational noise in random interactions in large groups leads to seven continuous families of (short run) Perfect Bayesian equilibria (PBE) that involve both vengeful and non-vengeful types. A new long run evolutionary equilibrium concept, Evolutionary Perfect Bayesian Equilibrium (EPBE), shrinks the equilibrium set to two points. In one EPBE, only the non-vengeful type survives and there are no mutual gains. In the other EPBE, both types survive and reap mutual gains.reciprocity; vengeance; evolutionary perfect Bayesian equilibrium; social dilemmas

The Evolutionary Stability of Optimism, Pessimism and Complete Ignorance

We provide an evolutionary foundation to evidence that in some situations humans maintain optimistic or pessimistic attitudes towards uncertainty and are ignorant to relevant aspects of the environment. Players in strategic games face Knightian uncertainty about opponents' actions and maximize individually their Choquet expected utility. Our Choquet expected utility model allows for both an optimistic or pessimistic attitude towards uncertainty as well as ignorance to strategic dependencies. An optimist (resp. pessimist) overweights good (resp. bad) outcomes. A complete ignorant never reacts to opponents' change of actions. With qualifications we show that optimistic (resp. pessimistic) complete ignorance is evolutionary stable / yields a strategic advantage in submodular (resp. supermodular) games with aggregate externalities. Moreover, this evolutionary stable preference leads to Walrasian behavior in those classes of games.ambiguity, Knightian uncertainty, Choquet expected utility, neo-additive capacity, Hurwicz criterion, Maximin, Minimax, Ellsberg paradox, overconfidence, supermodularity, aggregative games, monotone comparative statics, playing the field, evolution of preferences