Could cooperation among strangers be facilitated by adaptations that use sparse information to accurately predict cooperative behaviour? We hypothesise that predictions are influenced by beliefs, descriptions, appearance and behavioural history available for first and second impressions. We also hypothesise that predictions improve when more information is available. We conducted a two-part study. First, we recorded thin-slice videos of university students just before their choices in a repeated Prisoner's Dilemma with matched partners. Second, a worldwide sample of raters evaluated each player using videos, photos, only gender labels or neither images nor labels. Raters guessed players’ first-round Prisoner's Dilemma choices and then their second-round choices after reviewing first-round behavioural histories. Our design allows us to investigate incremental effects of gender, appearance and behavioural history gleaned during first and second impressions. Predictions become more accurate and better-than-chance when gender, appearance or behavioural history is added. However, these effects are not incrementally cumulative. Predictions from treatments showing player appearance were no more accurate than those from treatments revealing gender labels and predictions from videos were no more accurate than those from photos. These results demonstrate how people accurately predict cooperation under sparse information conditions, helping explain why conditional cooperation is common among strangers.

Researchers in the decision making tradition usually analyze multiple decisions within experiments by aggregating choices across individuals and using the individual subject as the unit of analysis. This approach can mask important variations and patterns within the data. Specifically, it ignores variations in decisions across a task or game and possible influences of characteristics of the subject or the experiment on these variations. We demonstrate, by reanalyzing data from two previously published articles, how a mixed model analysis addresses these limitations. Our results, with a modified Iowa gambling task and a prisoner's dilemma game, illustrate the ways in which such an analysis can test hypotheses not possible with other techniques, is more parsimonious, and is more likely to be faithful to theoretical models.

Prisoner's Dilemma (PD) games have become a well-established paradigm for studying the mechanisms by which cooperative behavior may evolve in societies consisting of selfish individuals. Recent research has focused on the effect of spatial and connectivity structure in promoting the emergence of cooperation in scenarios where individuals play games with their neighbors, using simple “memoryless” rules to decide their choice of strategy in repeated games. While heterogeneity and structural features such as clustering have been seen to lead to reasonable levels of cooperation in very restricted settings, no conditions on network structure have been established, which robustly ensure the emergence of cooperation in a manner that is not overly sensitive to parameters such as network size, average degree, or the initial proportion of cooperating individuals. Here, we consider a natural random network model, with parameters that allow us to vary the level of “community” structure in the network, as well as the number of high degree hub nodes. We investigate the effect of varying these structural features and show that, for appropriate choices of these parameters, cooperative behavior does now emerge in a truly robust fashion and to a previously unprecedented degree. The implication is that cooperation (as modelled here by PD games) can become the social norm in societal structures divided into smaller communities, and in which hub nodes provide the majority of inter-community connections.

Team reasoning is thought to be descriptively and normatively superior to the classical individualistic theory of rational choice primarily because it can recommend coordination on Hi in the Hi-Lo game and cooperation in Prisoner's Dilemma-type situations. However, left unanswered is whether it is rational for individuals to become team members, leaving a gap between reasons for individuals and reasons for team members. In what follows, I take up Susan Hurley's attempt to show that it is rational for an individual to become a team member. I argue that her account fails to show that becoming a team member is necessary to gain the advantages of coordination in Hi-Lo games or cooperation in Prisoner's Dilemma-type situations, and that individuals will often fare better reasoning as individual agents than as members of a team. I argue further that there is a more general problem for team reasoning, specifically that the conditions needed to make it rational for a team member to employ team reasoning make becoming a team member unnecessary.

Hobbes's own justification for the existence of governments relies on the assumption that without a government our lives in the state of nature would result in a state of war of every man against every man. Many contemporary scholars have tried to explain why universal war is unavoidable in Hobbes's state of nature by utilizing modern game theory. However, most game-theoretic models that have been presented so far do not accurately capture what Hobbes deems to be the primary cause of conflict in the state of nature—namely, uncertainty, rather than people's egoistic psychology. Therefore, I claim that any game-theoretic model that does not incorporate uncertainty into the picture is the wrong model. In this paper, I use Bayesian game theory to show how universal conflict can break out in the state of nature—even when the majority of the population would strictly prefer to cooperate and seek peace with other people—due to uncertainty about what type of person the other player is. Along the way, I show that the valuation of one's own life is one of the central mechanisms that drives Hobbes's pessimistic conclusion.

An integro-differential model for evolutionary dynamics with mutations is investigated by improving the understanding of its behaviour using numerical simulations. The proposed numerical approach can handle also density dependent fitness, and gives new insights about the role of mutation in the preservation of cooperation.

The search for extra-terrestrial intelligence (SETI) has been performed principally as a one-way survey, listening of radio frequencies across the Milky Way and other galaxies. However, scientists have engaged in an active messaging only rarely. This suggests the simple rationale that if other civilizations exist and take a similar approach to ours, namely listening but not broadcasting, the result is a silent universe. A simple game theoretical model, the prisoner's dilemma, explains this situation: each player (civilization) can passively search (defect), or actively search and broadcast (cooperate). In order to maximize the payoff (or, equivalently, minimize the risks) the best strategy is not to broadcast. In fact, the active search has been opposed on the basis that it might be dangerous to expose ourselves. However, most of these ideas have not been based on objective arguments, and ignore accounting of the possible gains and losses. Thus, the question stands: should we perform an active search? I develop a game-theoretical framework where civilizations can be of different types, and explicitly apply it to a situation where societies are either interested in establishing a two-way communication or belligerent and in urge to exploit ours. The framework gives a quantitative solution (a mixed-strategy), which is how frequent we should perform the active SETI. This frequency is roughly proportional to the inverse of the risk, and can be extremely small. However, given the immense amount of stars being scanned, it supports active SETI. The model is compared with simulations, and the possible actions are evaluated through the San Marino scale, measuring the risks of messaging.

Self-control, so important in the theory and practice of psychology, has usually been understood introspectively. This target article adopts a behavioral view of the self (as an abstract class of behavioral actions) and of self-control (as an abstract behavioral pattern dominating a particular act) according to which the development of self-control is a molar/molecular conflict in the development of behavioral patterns. This subsumes the more typical view of self-control as a now/later conflict in which an act of self-control is a choice of a larger but later reinforcer over a smaller but sooner reinforcer. If at some future time the smaller-sooner reinforcer will be more valuable than the larger-later reinforcer, self-control may be achieved through a commitment to the largerlater reinforcer prior to that point. According to some, there is a progressive internalization of commitment in the development of self-control. This presents theoretical and empirical problems. In two experiments – one with pigeons choosing between smallersooner and larger-later reinforcers, the other with adult humans choosing between short-term particular and long-term abstract reinforcers – temporal patterning of choices increased self-control.

Evolutionary game theory is a method of analysing the evolution of phenotypes (including types of behaviour) when the fitness of a particular phenotype depends onits frequency in the population. It was first applied to pairwise contests between animals. Such contests usually have some associated asymmetry, in size, prior residence, or age or sex status; the theory predicts that the asymmetry will be used as a cue to settlethe contest, and this is found to be the case. The theory can also be applied when individuals are competing against the population as a whole, or some part of it. In such cases, the evolution of variable behaviour - so-called mixed strategies - is predicted; actual examples of this are given. Game theory can be applied to the evolution of cooperative as well as of antagonistic behaviour. An analysis of the evolution of learning leads to testable predictions about learning behaviour.

Many situations in human life present choices between (a) narrowly preferred particular alternatives and (b) narrowly less preferred (or aversive) particular alternatives that nevertheless form part of highly preferred abstract behavioral patterns. Such alternatives characterize problems of self-control. For example, at any given moment, a person may accept alcoholic drinks yet also prefer being sober to being drunk over the next few days. Other situations present choices between (a) alternatives beneficial to an individual and (b) alternatives that are less beneficial (or harmful) to the individual that would nevertheless be beneficial if chosen by many individuals. Such alternatives characterize problems of social cooperation; choices of the latter alternative are generally considered to be altruistic. Altruism, like self-control, is a valuable temporally-extended pattern of behavior. Like self-control, altruism may be learned and maintained over an individual's lifetime. It needs no special inherited mechanism. Individual acts of altruism, each of which may be of no benefit (or of possible harm) to the actor, may nevertheless be beneficial when repeated over time. However, because each selfish decision is individually preferred to each altruistic decision, people can benefit from altruistic behavior only when they are committed to an altruistic pattern of acts and refuse to make decisions on a case-by-case basis.

A model of cooperation versus defection in a sequence of games is analysed under the assumptions that the rules of the game are randomly changed from one encounter to another, that the decisions are to be made each time anew, according to the (random) rules of the specific local game, and that the result of one such game affects the ability of a player to participate and thus, cooperate in the next game. Under plausible assumptions, it is shown that all Nash solutions of the supergame determine cooperation over a non-degenerate range of rules, determining encounters of the prisoner's dilemma type.