Kevin Zollman

Recent research into the evolution of higher cognition has piqued an interest in the effect of natural selection on the ability of creatures to respond to their environment. It is believed that environmental variation is required for plasticity to evolve in cases where the ability to be plastic is costly. We investigate one form of environmental variation: frequency dependent selection. Using tools in game theory, we investigate a few models of plasticity and outline the cases where selection would be expected to maintain it. Ultimately we conclude that frequency dependent selection is likely insuffcient to maintain plasticity given reasonable assumptions about its costs. This result is very similar to one aspect of the well-discussed Baldwin effect, where plasticity is first selected for and then later selected against. We show how in these models one would expect plasticity to grow in the population and then be later reduced. Ultimately we conclude that if one is to account for the evolution of behavioral plasticity in this way, one must appeal to a very particular sort of external environmental variation

In this paper we distinguish two competing conceptions of dignity, one recognizably Hobbesian and one recognizably Kantian. We provide a formal model of how decision-makers committed to these conceptions of dignity might reason when engaged in an economic transaction that is not inherently insulting, but in which it is possible for the dignity of the agent to be called into question. This is a modified version of the ultimatum game. We then use this model to illustrate ways in which the Kantian evaluative standpoint enjoys a kind of internal stability that the Hobbesian framework lacks. Our interpersonal argument shows that, under certain conditions, Hobbesians prefer to cultivate Kantian commitments in others and promote the presence of Kantians in the population. Our intrapersonal argument shows that agents who are conflicted between Kantian and Hobbesian commitments have powerful reasons not to resolve this commitment in favour of Hobbesian values. Our emulation argument illustrates that in repeated versions of the ultimatum game, the Hobbesian chooses to behave like a Kantian, including publicly repudiating her Hobbesian commitments. Here again, however, the Hobbesian is able to achieve a desired benefit only on the condition that there are genuine Kantians in the population. Finally, our social planning argument explores the reasons why a community of Hobbesians would opt to enshrine a Kantian conception of dignity into law. The paper concludes with some remarks about the policy implications of this work. The value or worth of a man is, as for all other things, his price, that is to say, so much as would be given for the use of his power; and therefore is not absolute, but a thing dependent on the need and judgement of another... The public worth of a man, which is the value set on him by the Common-wealth, is that which men commonly call DIGNITY. Hobbes, _Leviathan X_, 16

In this paper we show that there are certain limits as to what applications of Maynard Smith’s concept of evolutionarily stable strategy can tell us about evolutionary processes. We shall argue that ESS is very similar in spirit to a particular branch of rational choice game theory, namely, the literature on refinements of Nash equilibrium. In the first place, ESS can also be viewed as a Nash equilibrium refinement. At a deeper level, ESS shares a common structure with other rational choice equilibrium refinements. An equilibrium is evaluated according to whether it persists under specific kinds of perturbations. In the case of ESS, these perturbations are mutations. However, from a dynamical point of view, focusing exclusively on perturbations of equilibria provides only a partial account of the system under consideration. We will show that this has important consequences when it comes to analyzing game-theoretic models of evolutionary processes. In particular, there are non-ESS states which are significant for evolutionary dynamics

The handicap principle has come under significant challenge both from empirical studies and from theoretical work. As a result, a number of alternative explanations for honest signaling have been proposed. This paper compares the evolutionary plausibility of one such alternative, the "hybrid equilibrium," to the handicap principle. We utilize computer simulations to compare these two theories as they are instantiated in Maynard Smith's Sir Philip Sidney game. We conclude that, when both types of communication are possible, evolution is unlikely to lead to handicap signaling and is far more likely to result in the partially honest signaling predicted by hybrid equilibrium theory

This paper examines and contrasts two closely related evolutionary explanations in human behaviour: signalling theory, and the theory of Credibility Enhancing Displays. Both have been proposed to explain costly, dangerous, or otherwise ‘extravagant’ social behaviours, especially in the context of religious belief and practice, and each have spawned significant lines of empirical research. However, the relationship between these two theoretical frameworks is unclear, and research which engages both of them is largely absent. In this paper we seek to address this gap at the theoretical level, examining the core differences between the two approaches and prospects and conditions for future empirical testing. We clarify the dynamical and mechanistic bases of signalling and CREDs as explanatory models and contrast the previous uses to which they have been put in the human sciences. Because of idiosyncrasies regarding those uses, several commonly supposed differences and comparative advantages are actually misleading and not in fact generalisable. We also show that signalling and CREDs theories as explanatory models are not interchangeable, because of deep structural differences. As we illustrate, the proposed causal networks of each theory are distinct, with important differences in the endogeneity of various phenomena within each model and their explanatory targets. As a result, they can be seen as complementary rather than in competition. We conclude by surveying the current state of the literature and identifying the differential predictions which could underpin more comprehensive empirical comparison in future research.

Lewis signaling games illustrate how language might evolve from random behavior. The probability of evolving an optimal signaling language is, in part, a function of what learning strategy the agents use. Here we investigate three learning strategies, each of which allows agents to forget old experience. In each case, we find that forgetting increases the probability of evolving an optimal language. It does this by making it less likely that past partial success will continue to reinforce suboptimal practice. The learning strategies considered here show how forgetting past experience can promote learning in the context of games with suboptimal equilibria.