In a dyadic game, strategic asymmetric dominance occurs when a player's preference for one strategy A relative to another B is systematically increased by the addition of a third strategy Z, strictly dominated by A but not by B. There are theoretical and empirical grounds for believing that this effect should decline over repetitions, and other grounds for believing, on the contrary, that it should persist. To investigate this question experimentally, 30 participant pairs played 50 rounds of one symmetric and two asymmetric 3 × 3 games each having one strategy strictly dominated by one other, and a control group played 2 × 2 versions of the same games with dominated strategies removed. The strategic asymmetric dominance effect was observed in the repeated-choice data: dominant strategies in the 3 × 3 versions were chosen more frequently than the corresponding strategies in the 2 × 2 versions. Time series analysis revealed a significant decline in the effect over repetitions in the symmetric game only. Supplementary verbal protocol analysis helped to clarify the players’ reasoning and to explain the results.

We examine strategic sophistication using eight two-person 3 × 3 one-shot games. To facilitate strategic thinking, we design a ‘structured’ environment where subjects first assign subjective values to the payoff pairs and state their beliefs about their counterparts’ probable strategies, before selecting their own strategies in light of those deliberations. Our results show that a majority of strategy choices are inconsistent with the equilibrium prediction, and that only just over half of strategy choices constitute best responses to subjects’ stated beliefs. Allowing for other-regarding considerations increases best responding significantly, but the increase is rather small. We further compare patterns of strategies with those made in an ‘unstructured’ environment in which subjects are not specifically directed to think strategically. Our data suggest that structuring the pre-decision deliberation process does not affect strategic sophistication.

Trolley problems have been used in the development of moral theory and the psychological study of moral judgments and behavior. Most of this research has focused on people from the West, with implicit assumptions that moral intuitions should generalize and that moral psychology is universal. However, cultural differences may be associated with differences in moral judgments and behavior. We operationalized a trolley problem in the laboratory, with economic incentives and real-life consequences, and compared British and Chinese samples on moral behavior and judgment. We found that Chinese participants were less willing to sacrifice one person to save five others, and less likely to consider such an action to be right. In a second study using three scenarios, including the standard scenario where lives are threatened by an on-coming train, fewer Chinese than British participants were willing to take action and sacrifice one to save five, and this cultural difference was more pronounced when the consequences were less severe than death.

Theories of trust distinguish general trust in situations of social uncertainty from assurance-based trust in committed, long-term relationships. This study investigates European-Japanese differences using the Centipede game, in which two players choose between cooperation and defection. The game models repeated reciprocal interactions, necessitating assurance-based trust to sustain cooperation. We included game conditions offering players the option of purchasing commitment-enhancing tools to increase social certainty. Japanese participants were more cooperative than Europeans, confirming higher assurance-based trust, and also purchased more commitment-enhancing tools, demonstrating their preferences for social certainty. Purchase of commitment-enhancing tools improved cooperativeness in both groups. However, if co-players refused tool purchase, the Japanese appeared to interpret this as non-cooperative intent and cooperativeness in the respective games decreased.

In a recent article in this journal, Duijf claims to have proved that team reasoning can be viewed as a payoff transformation. His formalization mimics team reasoning but ignores its essential agency switch. The possibility of such a payoff transformation was never in doubt, does not imply that team reasoning can be viewed as a payoff transformation, and makes no sense in a game in which payoffs represent players’ utilities. A theorem is proved here that a simpler and more intuitive payoff transformation can mimic any theory that predicts what strategies players will choose in a well-defined game.

Puzzlement about extreme self-sacrifice arises from an unarticulated assumption of psychological egoism, according to which people invariably act in their own self-interests. However, altruism and collective rationality are well established experimentally: people sometimes act to benefit others or in the interests of groups to which they belong. When such social motives are sufficiently strong, extreme self-sacrifice presents no special problem of explanation and does not require out-group threats.

Rapidly accumulating Holocene sediments in estuaries commonly are difficult to sample and date. In Chesapeake Bay, we obtained sediment cores as much as 20 m in length and used numerous radiocarbon ages measured by accelerator mass spectrometry methods to provide the first detailed chronologies of Holocene sediment accumulation in the bay. Carbon in these sediments is a complex mixture of materials from a variety of sources. Analyses of different components of the sediments show that total organic carbon ages are largely unreliable, because much of the carbon (including coal) has been transported to the bay from upstream sources and is older than sediments in which it was deposited. Mollusk shells (clams, oysters) and foraminifera appear to give reliable results, although reworking and burrowing are potential problems. Analyses of museum specimens collected alive before atmospheric nuclear testing suggest that the standard reservoir correction for marine samples is appropriate for middle to lower Chesapeake Bay. The biogenic carbonate radiocarbon ages are compatible with 210Pb and 137Cs data and pollen stratigraphy from the same sites.

Post-settlement changes in sediment transport and accumulation is an important environmental issue in many estuaries, including the Chesapeake. Our data show that large variations in sediment mass accumulation rates occur among sites. At shallow water sites, local factors seem to control changes in accumulation rates with time. Our two relatively deep-water sites in the axial channel of the bay have different long-term average accumulation rates, but the history of sediment accumulation at these sites appears to reflect overall conditions in the bay. Mass accumulation rates at the two deep-water sites rapidly increased by about fourfold coincident with widespread land clearance for agriculture in the Chesapeake watershed.

There is a long-standing debate in philosophy about whether it is morally permissible to harm one person in order to prevent a greater harm to others and, if not, what is the moral principle underlying the prohibition. Hypothetical moral dilemmas are used in order to probe moral intuitions. Philosophers use them to achieve a reflective equilibrium between intuitions and principles, psychologists to investigate moral decision-making processes. In the dilemmas, the harms that are traded off are almost always deaths. However, the moral principles and psychological processes are supposed to be broader than this, encompassing harms other than death. Further, if the standard pattern of intuitions is preserved in the domain of economic harm, then that would open up the possibility of studying behaviour in trolley problems using the tools of experimental economics. We report the results of two studies designed to test whether the standard patterns of intuitions are preserved when the domain and severity of harm are varied. Our findings show that the difference in moral intuitions between bystander and footbridge scenarios is replicated across different domains and levels of physical and non-physical harm, including economic harms.

Normative theories can be useful in developing descriptive theories, as when normative subjective expected utility theory is used to develop descriptive rational choice theory and behavioral game theory. “Ought” questions are also the essence of theories of moral reasoning, a domain of higher mental processing that could not survive without normative considerations.

Mealey's interesting interpretation of sociopathy is based on an inappropriate two-person game model. A multiperson, compound game version of Chicken would be more suitable, because a population engaging in random pairwise interactions with that structure would evolve to an equilibrium in which a fixed proportion of strategic choices was exploitative, antisocial, and risky, as required by Mealey's interpretation.

Even if game theory is broadened to encompass other-regarding preferences, it cannot adequately model all aspects of interactive decision making. Payoff dominance is an example of a phenomenon that can be adequately modeled only by departing radically from standard assumptions of decision theory and game theory – either the unit of agency or the nature of rationality.

Psychological game theory encompasses formal theories designed to remedy game-theoretic indeterminacy and to predict strategic interaction more accurately. Its theoretical plurality entails second-order indeterminacy, but this seems unavoidable. Orthodox game theory cannot solve payoff-dominance problems, and remedies based on interval-valued beliefs or payoff transformations are inadequate. Evolutionary game theory applies only to repeated interactions, and behavioral ecology is powerless to explain cooperation between genetically unrelated strangers in isolated interactions. Punishment of defectors elucidates cooperation in social dilemmas but leaves punishing behavior unexplained. Team reasoning solves problems of coordination and cooperation, but aggregation of individual preferences is problematic.

Rational choice theory enjoys unprecedented popularity and influence in the behavioral and social sciences, but it generates intractable problems when applied to socially interactive decisions. In individual decisions, instrumental rationality is defined in terms of expected utility maximization. This becomes problematic in interactive decisions, when individuals have only partial control over the outcomes, because expected utility maximization is undefined in the absence of assumptions about how the other participants will behave. Game theory therefore incorporates not only rationality but also common knowledge assumptions, enabling players to anticipate their co-players' strategies. Under these assumptions, disparate anomalies emerge. Instrumental rationality, conventionally interpreted, fails to explain intuitively obvious features of human interaction, yields predictions starkly at variance with experimental findings, and breaks down completely in certain cases. In particular, focal point selection in pure coordination games is inexplicable, though it is easily achieved in practice; the intuitively compelling payoff-dominance principle lacks rational justification; rationality in social dilemmas is self-defeating; a key solution concept for cooperative coalition games is frequently inapplicable; and rational choice in certain sequential games generates contradictions. In experiments, human players behave more cooperatively and receive higher payoffs than strict rationality would permit. Orthodox conceptions of rationality are evidently internally deficient and inadequate for explaining human interaction. Psychological game theory, based on nonstandard assumptions, is required to solve these problems, and some suggestions along these lines have already been put forward.

A significant increase in the probability of an action resulting from observing that action performed by another agent cannot, on its own, provide persuasive evidence of imitation. Simple models of social influence based on two-person sequential games suggest that both imitation and pseudo-imitation can be explained by a process more fundamental than priming, namely, subjective utility maximization.