Competition for scarce resources in the face of birth and death (the struggle for survival) has shaped social and economic interaction since the beginnings of mankind. This research is the first to induce selection pressure in controlled strategic decision-making experiments using performance-based replacement of participants over time. Strategic decision-making with and without selection pressure is considered in repeated Tullock-type rent seeking contests. Tullock contests’ incentive structure drives a wedge between profit maximization and survival. Moreover, there is a large number of past experiments without selection pressure demonstrating a willingness to compete that cannot be justified by profit maximization alone and thus seemingly supports evolutionary game-theoretic predictions. Surprisingly, we find that the intensity of competition in repeated contests does in fact decrease once selection pressure is added. Participants’ behavior under selection pressure is well-approximated by the finite population evolutionarily stable strategy (ESS) of the stage game. This happens because a significant share of contestants quickly adapt to survive under selection pressure at the expense of new entrants. By contrast, when selection pressure is absent, we observe a large variance in competitiveness and frequent competition far beyond profit-maximizing levels. Selection pressure has a disciplining effect on contestants’ decision-making, boosting not only the lifespans of successful contestants but also average round payoffs across the entire population.
Holdahl, E., van den Nouweland, A. Minimally incomplete sampling and convergence of adaptive play in games. Econ Theory Bull (2024). DOI:10.1007/s40505-024-00262-0.
Adaptive learning (cf. Young [1993]) explains how conventions emerge in populations in which players sample a sufficiently small portion of the recent plays and best reply to those samples. Stochastically stable conventions are those that are most likely to be established and persevere in the long run when the model includes perturbations in the form of players sometimes making a mistake and choosing an action that is not a best response to their sample. Young [1993] has given rise to a large body of work in which adaptive learning is used to examine which conventions emerge in a variety of games.
In this literature, the bound that players sample at most half of the plays available to them is prevalent, although some work includes stricter bounds on the incompleteness of sampling.
We examine the case of 2 × 2 coordination games, for which Young [1993] employs the bound that at most half of all available plays are sampled. We establish that this bound is unnecessarily strict, because any degree of incomplete sampling is sufficient for a convention to be established. Moreover, relaxing the limitations on sampling does not affect which conventions are stochastically stable.
Holdahl, Ethan & Wu, Jiabin. (2023). Conflicts, assortative matching, and the evolution of signaling norms. Journal of Economic Interaction and Coordination. 1-23. DOI:10.1007/s11403-023-00384-x.
This paper proposes a model to explain the potential role of inter-group conflicts in determining the rise and fall of signaling norms. Individuals in a population are characterized by high and low productivity types and they are matched in pairs to form social relationships such as mating or foraging relationships. In each relationship, an individual’s payoff is increasing in its own type and its partner’s type. Hence, the payoff structure of a relationship does not resemble a dilemma situation. Assume that types are not observable. In one population, assortative matching according to types is sustained by signaling. In the other population, individuals do not signal and they are randomly matched. Types evolve within each population. At the same time, the two populations may engage in conflicts. Due to assortative matching, high types grow faster in the population with signaling, yet they bear the cost of signaling, which lowers their population’s fitness in the long run. Through simulations, we show that the survival of the signaling population depends crucially on the timing and the efficiency of weapons used in inter-group conflicts.
Binder, S., Holdahl, E., Trinh, L., & Smith, J. H. (2020). Humanity’s Fundamental Environmental Limits. Human Ecology, 48(2), 235-244. DOI:10.1007/s10745-020-00140-w.
Models and estimates of Earth’s human carrying capacity vary widely and assume, rather than solve for, binding environmental constraints (the process or resource in shortest supply relative to human biological needs). The binding constraint, and therefore the true upper bound on the number of humans that Earth could sustain indefinitely, remains unknown. We seek to resolve this uncertainty by considering a full range of technological possibilities and incorporating a potential stoichiometric constraint not previously explored. We find that limits to photosynthesis constrain population before micronutrients become limiting unless technological capabilities for utilizing nutrient resources lag far behind other technologies. With ideal technology, human carrying capacity runs into the tens of trillions, while with currently demonstrated technology Earth could support more than 200 billion humans. These numbers reflect neither a desirable nor a natural equilibrium population level, but represent a rough estimate of the maximum number of humans Earth could sustain.
Contributions include creating the Photosynthetically Active Radiation daily average data set, a key input to the primary function of the paper, using a novel algorithm. Check out my largest contribution summarized in a Shiny App here!
Games with multiple equilibria introduce the potential for populations to get stuck in inefficient outcomes. In theory, the introduction of additional equilibria, "stepping stones", could pave the way for a smoother and less risky transition. I run a lab experiment to test if the introduction of these “stepping stones”, can facilitate transitions from an inefficient but safe equilibrium to a risky, payoff dominant equilibrium. I employ different payoffs for the transition strategy and examine the effects that different degrees of information about the game have on group's play. I find evidence that adding these "stepping stones" does help populations transition to the efficient equilibria. I also find that when groups have more information about each other's payoffs they are able to transition to the efficient equilibria faster and are less prone to cyclical behavior.
This paper studies a preference evolution model in which a population of agents are matched to play a sequential prisoner's dilemma in an incomplete information environment. An institution can design an incentive-compatible screening scheme, such as a special zone that requires an entry fee, or a costly label for purchase, to segregate the conditional cooperators from the non-cooperators. We show that institutional intervention of this sort can help the conditional cooperators to prevail when the psychological benefit of cooperating for them is sufficiently strong and the membership of the special zone or the label is inheritable with a sufficiently high probability.
In this study, we experimentally explore the impact of AI as a supportive tool for players
in a two-player trust game. The game begins with the trustee sending a message to the
trustor. In certain scenarios, the trustee is aided by the large language model (LLM)
ChatGPT in composing this message. In other scenarios, the trustor uses AI to interpret
the message from the trustee, or both players may have access to AI assistance. Our
findings indicate that when the trustee utilizes AI as a helper, it enhances cooperation
with the trustor. Interestingly, this improvement in cooperation is not attributed to AI’s
superior messaging skills. Instead, when the trustee has AI assistance, it may encourage
the trustor to scrutinize the trustee’s message more closely. The detailed scrutiny by
the trustor, and potentially the trustee’s awareness of this scrutiny, aligns the beliefs
of the trustor and the trustee, thereby fostering an environment that encourages the
development of trust.
Works in Progress
Graphically Solving for Mixed Nash Equilibria in 2x2 Games
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