Time to fly: A comparison of marginal value theorem approximations in an agent-based model of foraging waterfowl

One of the fundamental decisions foragers face is how long an individual should remain in a given foraging location. Typical approaches to modeling this decision are based on the marginal value theorem. However, direct application of this theory would require omniscience regarding food availability. Even with complete knowledge of the environment, foraging with intraspecific competition requires resolution of simultaneous circular dependencies. In response to these issues in application, a number of approximating algorithms have been proposed, but it remains to be seen whether these algorithms are effective given a large number of foragers with realistic characteristics. We implemented several algorithms approximating marginal value foraging in a large-scale avian foraging model and compared the results. We found that a novel reinforcement-learning algorithm that includes cost of travel is the most effective algorithm that most closely approximates marginal value foraging theory and recreates depletion patterns observed in empirical studies

Toward a Theory of the Evolution of Fair Play

Juvenile animals of many species engage in social play, but its functional significance is not well understood. This is especially true for a type of social play called fair play (Fp). Social play often involves behavioral patterns similar to adult behaviors (e.g., fighting, mating, and predatory activities), but young animals often engage in Fp behaviors such as role-reversals and self-handicapping, which raises the evolutionary problem of why Fp exists. A long-held working hypothesis, tracing back to the 19th century, is that social play provides contexts in which adult social skills needed for adulthood can be learned or, at least, refined. On this hypothesis, Fp may have evolved for adults to acquire skills for behaving fairly in the sense of equitable distribution of resources or treatment of others. We investigated the evolution of Fp using an evolutionary agent-based model of populations of social agents that learn adult fair behavior (Fb) by engaging in Fp as juveniles. In our model, adults produce offspring by accumulating resources over time through foraging. Adults can either behave selfishly by keeping the resources they forage or they can pool them, subsequently dividing the pooled resources after each round of foraging. We found that fairness as equitability was beneficial especially when resources were large but difficult to obtain and led to the evolution of Fp. We conclude by discussing the implications of this model, for developing more rigorous theory on the evolution of social play, and future directions for theory development by modeling the evolution of play

A Self-Organising Model of Thermoregulatory Huddling

Endotherms such as rats and mice huddle together to keep warm. The huddle is considered to be an example of a self-organising system, because complex properties of the collective group behaviour are thought to emerge spontaneously through simple interactions between individuals. Groups of rodent pups display two such emergent properties. First, huddling undergoes a ‘phase transition’, such that pups start to aggregate rapidly as the temperature of the environment falls below a critical temperature. Second, the huddle maintains a constant ‘pup flow’, where cooler pups at the periphery continually displace warmer pups at the centre. We set out to test whether these complex group behaviours can emerge spontaneously from local interactions between individuals. We designed a model using a minimal set of assumptions about how individual pups interact, by simply turning towards heat sources, and show in computer simulations that the model reproduces the first emergent property—the phase transition. However, this minimal model tends to produce an unnatural behaviour where several smaller aggregates emerge rather than one large huddle. We found that an extension of the minimal model to include heat exchange between pups allows the group to maintain one large huddle but eradicates the phase transition, whereas inclusion of an additional homeostatic term recovers the phase transition for large huddles. As an unanticipated consequence, the extended model also naturally gave rise to the second observed emergent property—a continuous pup flow. The model therefore serves as a minimal description of huddling as a self-organising system, and as an existence proof that group-level huddling dynamics emerge spontaneously through simple interactions between individuals. We derive a specific testable prediction: Increasing the capacity of the individual to generate or conserve heat will increase the range of ambient temperatures over which adaptive thermoregulatory huddling will emerge

Evaluating everyday explanations

People frequently rely on explanations provided by others to understand complex phenomena. A fair amount of attention has been devoted to the study of scientific explanation, and less on understanding how people evaluate naturalistic, everyday explanations. Using a corpus of diverse explanations from Reddit's "Explain Like I'm Five" and other online sources, we assessed how well a variety of explanatory criteria predict judgments of explanation quality. We find that while some criteria previously identified as explanatory virtues do predict explanation quality in naturalistic settings, other criteria, such as simplicity, do not. Notably, we find that people have a preference for complex explanations that invoke more causal mechanisms to explain an effect. We propose that this preference for complexity is driven by a desire to identify enough causes to make the effect seem inevitable

Causality, Determinism, and the Mind-Brain Problem

The problem of causality, determinism, and mind and brain are discussed, and new solutions are offered. To begin, a pragmatic structuralism is assumed, asserting the functional equivalence of mind and brain activity. A problem-solving model of mind-brain activity is defined, employing the mathematical theory of probablistic automata. With this model it can be determined whether mind-brain activity is deterministic. This is accomplished if an adequate definition of strict causality is developed. Logical models of strict causality which define the causal relation in terms of material implication or strict implication are rejected. Causal relativity is assumed, and certain systemtheoretical assumptions are made with respect to the problem-solving model of mind-brain activity. Thus, strict causal structures are deterministic if the etiologic relation ↔ is representable by a function which is (1) irreflexive, (2) transitive, (3) asymmetric, and (4) temporally ordered. The representing function must be one-one or many-one, and ↔ must be relativated to a model, L, and a domain, D. The results are, the representing functions of the models are not one-one or many-one, and thus mind-brain activity is indeterministic. But to avoid the result that mind-brain systems are chaotic in their behavior, the problem-solving model of mind-brain activity is given a gametheoretical interpretation

A model of the evolution of equitable offers in n-person dictator games with interbirth intervals.

People are often generous even when it is not in their apparent self-interest to do so as demonstrated by numerous experiments using the dictator game (DG). More recent research using DGs has varied the number of dictators and recipients and used these games to investigate the bystander effect and congestible altruism. These studies have found that people are less generous when there are others who could be generous (the bystander effect) and also less generous when there are multiple recipients (congestible altruism) though the sum of their generosity to all recipients increases. A working hypothesis is proposed that the context-sensitive generosity observed in n-person DGs can be explained as equitable behavior. From an evolutionary perspective, explaining the evolution of equitable behavior is challenging at best. To provide an evolutionary explanation, a second working hypothesis is proposed: equitable offers evolve because they reduce resource deficits produced by variability in the accumulation of resources and thereby minimize the length of interbirth intervals (IBIs) and increase fitness. Based on this working hypothesis, an evolutionary model was developed for n-person DGs to investigate the evolution of equitable offers as a resource allocation problem when reproduction is constrained by IBIs. Simulations demonstrated that equitable offers could evolve in group-structured populations when there is a cost (i.e., longer IBIs) to running resource deficits. Mean evolved offers also varied as a function of the number of dictators and recipients in patterns consistent with the bystander effect and congestible altruism. Equitable offers evolved because they reduced resource variability among group members and thereby reduced resource deficits, which insured higher average rates of reproduction for more equitable groups of agents. Implications of these results are discussed

A model of the evolution of equitable offers in n-person dictator games with interbirth intervals.

People are often generous even when it is not in their apparent self-interest to do so as demonstrated by numerous experiments using the dictator game (DG). More recent research using DGs has varied the number of dictators and recipients and used these games to investigate the bystander effect and congestible altruism. These studies have found that people are less generous when there are others who could be generous (the bystander effect) and also less generous when there are multiple recipients (congestible altruism) though the sum of their generosity to all recipients increases. A working hypothesis is proposed that the context-sensitive generosity observed in n-person DGs can be explained as equitable behavior. From an evolutionary perspective, explaining the evolution of equitable behavior is challenging at best. To provide an evolutionary explanation, a second working hypothesis is proposed: equitable offers evolve because they reduce resource deficits produced by variability in the accumulation of resources and thereby minimize the length of interbirth intervals (IBIs) and increase fitness. Based on this working hypothesis, an evolutionary model was developed for n-person DGs to investigate the evolution of equitable offers as a resource allocation problem when reproduction is constrained by IBIs. Simulations demonstrated that equitable offers could evolve in group-structured populations when there is a cost (i.e., longer IBIs) to running resource deficits. Mean evolved offers also varied as a function of the number of dictators and recipients in patterns consistent with the bystander effect and congestible altruism. Equitable offers evolved because they reduced resource variability among group members and thereby reduced resource deficits, which insured higher average rates of reproduction for more equitable groups of agents. Implications of these results are discussed