Gary Bornstein

Individual and Group Behavior in the Ultimatum Game: Are Groups More “Rational” Players?

This article reports two experiments that compared the standard ultimatum game played by individuals with the same game played by three-person groups. In the group treatment, the members of the allocating group conducted a brief, face-to-face discussion in order to decide, as a group, on a proposed division, whereas the members of recipient group held a discussion on whether to accept or reject the proposal. If the proposal was accepted, each group member received an equal share of his groups payoff (the pie in the group condition was three times that in the individual condition). In both experiments, groups offered less than individuals. But as indicated by the low rejection rate in both treatments, groups were also willing to accept less.

Intergroup Conflict: Individual, Group, and Collective Interests

Intergroup conflicts generally involve conflicts of interests within the competing groups as well. This article outlines a taxonomy of games, called team games, which incorporates the intragroup and intergroup levels of conflict. Its aims are to provide a coherent framework for analyzing the prototypical problems of cooperation and competition that arise within and between groups, and to review an extensive research program that has used this framework to study individual and group behavior in the laboratory. Depending on the games payoff structure, contradictions or conflicts are created among the rational choices at the individual, group, and collective levels—a generalization of the contradiction between individual and collective rationality occurring in the traditional mixed-motive games. These contradictions are studied so as to identify the theoretical and behavioral conditions that determine which level of rationality prevails.

The oxytocin receptor (OXTR) contributes to prosocial fund allocations in the dictator game and the social value orientations task.

Background Economic games observe social decision making in the laboratory that involves real money payoffs. Previously we have shown that allocation of funds in the Dictator Game (DG), a paradigm that illustrates costly altruistic behavior, is partially determined by promoter-region repeat region variants in the arginine vasopressin 1a receptor gene (AVPR1a). In the current investigation, the gene encoding the related oxytocin receptor (OXTR) was tested for association with the DG and a related paradigm, the Social Values Orientation (SVO) task. Methodology/Principal Findings Association (101 male and 102 female students) using a robust-family based test between 15 single tagging SNPs (htSNPs) across the OXTR was demonstrated with both the DG and SVO. Three htSNPs across the gene region showed significant association with both of the two games. The most significant association was observed with rs1042778 (p = 0.001). Haplotype analysis also showed significant associations for both DG and SVO. Following permutation test adjustment, significance was observed for 2–5 locus haplotypes (p<0.05). A second sample of 98 female subjects was subsequently and independently recruited to play the dictator game and was genotyped for the three significant SNPs found in the first sample. The rs1042778 SNP was shown to be significant for the second sample as well (p = 0.004, Fishers exact test). Conclusions The demonstration that genetic polymorphisms for the OXTR are associated with human prosocial decision making converges with a large body of animal research showing that oxytocin is an important social hormone across vertebrates including Homo sapiens. Individual differences in prosocial behavior have been shown by twin studies to have a substantial genetic basis and the current investigation demonstrates that common variants in the oxytocin receptor gene, an important element of mammalian social circuitry, underlie such individual differences.

The Effect of Intergroup Competition on Group Coordination: An Experimental Study

We report an experiment on the effect of intergroup competition on group coordination in the minimal-effort game (Van Huyck et al., 1990). The competition was between two 7-person groups. Each player in each group independently chose an integer from 1 to 7. The group with the higher minimum won the competition and each of its members was paid according to the game?s original payoff matrix. Members of the losing group were paid nothing. In case of a tie, each player was paid half the payoff in the original matrix. This treatment was contrasted with two control treatments where each of the two groups played an independent coordination game, either with or without information about the minimum chosen by the outgroup. Although the intergroup competition does not change the set of strict equilibria, we found that it improved collective rationality by moving group members in the direction of higher-payoff equilibria. Merely providing group members with information about the minimal-effort level in the other group was not sufficient to generate this effect.

Individual and group decisions in the centipede game: Are groups more rational players?

Two experiments compared the Centipede game played either by 2 individuals or by 2 (3-person) groups. The 2 competitors alternate in deciding whether to take the larger portion of an increasing (or constant) pile of money, and as soon as one “takes” the game ends. Assuming that both sides are concerned only with maximizing their own payoffs (and that this is common knowledge), the game theoretic solution, derived by backward induction, is for the first mover to exit the game at the first decision node. Both experiments found that although neither individuals nor groups fully complied with this solution, groups did exit the game significantly earlier than individuals. The study of experimental games has uncovered many instances in which individuals deviate systematically from the game theoretic solution. This study is in accord with other recent experiments in suggesting that game theory may provide a better description of group behavior.

Molecular genetic studies of the arginine vasopressin 1a receptor (AVPR1a) and the oxytocin receptor (OXTR) in human behaviour: from autism to altruism with some notes in between

Converging evidence from both human and animal studies has highlighted the pervasive role of two neuropeptides, oxytocin (OXT) and arginine vasopressin (AVP), in mammalian social behaviours. Recent molecular genetic studies of the human arginine vasopressin 1a (AVPR1a) and oxytocin (OXTR) receptors have strengthened the evidence regarding the role of these two neuropeptides in a range of normal and pathological behaviours. Significant association between both AVPR1a repeat regions and OXTR single nucleotide polymorphisms (SNPs) with risk for autism has been provisionally shown which was mediated by socialization skills in our study. AVPR1a has also been linked to eating behaviour in both clinical and non-clinical groups, perhaps reflecting the social and ritualistic side of eating behaviour. Evidence also suggests that repeat variations in AVPR1a are associated with two other social domains in Homo sapiens: music and altruism. AVPR1a was associated with dance and musical cognition which we theorize as reflecting the ancient role of this hormone in social interactions executed by vocalization, ritual movement and dyadic (mother-offspring) and group communication. Finally, we have shown that individual differences in allocation of funds in the dictator game, a laboratory game of pure altruism, is predicted by length of the AVPR1a RS3 promoter-region repeat echoing the mechanism of this hormones action in the vole model of affiliative behaviours and facilitation of positive group interactions. While still in its infancy, the current outlook for molecular genetic investigations of AVP-OXT continues to be fascinating. Future studies should profitably focus on pharmacogenomic and genomic imaging strategies facilitated by the ease and efficacy of manipulating AVP-OXT neurotransmission by intranasal administration. Importantly, physiological measures, behavioural paradigms and brain activation can be informed by considering between-group and also within-group individual differences defined by common polymorphisms. Ultimately, investigators should strive to develop a cohesive model explaining how genomic variations are translated into individual and group differences in higher-order social behaviours.

Intergroup Competition for the Provision of Binary Public Goods

An experimental paradigm is proposed for investigating interpersonal conflicts under conditions of intergroup competition. The paradigm constitutes an n-person game with imperfect and incomplete information in which the n players arc divided into two groups, are each assigned monetary endowment, and must then decide independently and anonymously whether to keep the endowment or contribute it to the groups benefit. The group with the larger sum of contributions is provided with a monetary reward (binary public good), which is shared equally among all of its members regardless of their decision. Two alternative models are proposed and their testable implications are derived and discussed. Both assume maximization of expected utility, but their assumptions about the expectations each player holds about the decisions of the remaining players are different. The effects of predccisional communication arc examined and several extensions of the basic paradigm are outlined. Although the interest of social psychologists in intergroup relations has been growing rapidly (Billi~, 1976; Brewer, 1979; Tajfel, 1982), the experimental research in this area is still sparse, especially when compared with the vast amount of research on interpersonal relations (Rabbie, 1982). The difficulty of simulating complex intergroup relations in the laboratory is one reason for the fields slow development (Gerard & Miller, 1967; Rabbie, 1982). Another and perhaps more important reason appears to be the lack of an integrated theory. Thus, Rabbie (1982) wrote: Although the literature offers a number of hypotheses about intergroup relations, these hypotheses do not form an integrated theory. They are usually stated at one particular level of analysis, they are sometimes contradictory, and their supporting evidence varies widely. (p. 124) The development of an integrated theory has been especially hindered by the traditional distinction between the interpersonal and intergroup levels of analysis. This distinction has characterized the theoretical study and experimental investigation of social conflicts and competitions for many years (Tajfel, 1982). Despite recent attempts to simultaneously investigate the interpersonal and intergroup aspects of social conflicts in small groups (Brewer & Kramcr, 1986; Kramer & Brewer, 1984), the literature shows little success in closing the gap between these two largely hypothetical levels of analysis. One possible way to narrow the gap is by designing and conducting systematic and theory-driven research of social situations involving small groups, in which social conflicts occur simultaneously at both levels of analysis. Extending the paradigm

Oxytocin, but not vasopressin, increases both parochial and universal altruism

In todays increasingly interconnected world, deciding with whom and at what level to cooperate becomes a matter of increasing importance as societies become more globalized and large-scale cooperation becomes a viable means of addressing global issues. This tension can play out via competition between local (e.g. within a group) and global (e.g., between groups) interests. Despite research highlighting factors influencing cooperation in such multi-layered situations, their biological basis is not well understood. In a double-blind placebo controlled study, we investigated the influence of intranasally administered oxytocin and arginine vasopressin on cooperative behavior at local and global levels. We find that oxytocin causes an increase in both the willingness to cooperate and the expectation that others will cooperate at both levels. In contrast, participants receiving vasopressin did not differ from those receiving placebo in their cooperative behavior. Our results highlight the selective role of oxytocin in intergroup cooperative behavior.

AVPR1A Variant Associated with Preschoolers' Lower Altruistic Behavior

The genetic origins of altruism, defined here as a costly act aimed to benefit non-kin individuals, have not been examined in young children. However, previous findings concerning adults pointed at the arginine vasopressin receptor 1A (AVPR1A) gene as a possible candidate. AVPR1A has been associated with a range of behaviors including aggressive, affiliative and altruistic phenotypes, and recently a specific allele (327 bp) of one of its promoter region polymorphisms (RS3) has been singled out in particular. We modeled altruistic behavior in preschoolers using a laboratory-based economic paradigm, a modified dictator game (DG), and tested for association between DG allocations and the RS3 “target allele.” Using both population and family-based analyses we show a significant link between lower allocations and the RS3 “target allele,” associating it, for the first time, with a lower proclivity toward altruistic behavior in children. This finding helps further the understanding of the intricate mechanisms underlying early altruistic behavior.

Within- and between-group communication in intergroup competition for public goods

Abstract Eighty groups of subjects participated in a social dilemma game, where two groups competed with each other for the provision of a binary public good. Subjects were allowed to discuss the conflict before deciding privately and anonymously whether to contribute to their group benefit. In one condition preplay communication was restricted to ingroup members; in another condition all members of the two competing groups discussed the dilemma jointly with no opportunity for separate within-group discussions; and in three other conditions various combinations of within- and between-group preplay communication were allowed. Within-group communication maximized contribution rate but minimized collective outcome, whereas between-group communication had the opposite effect. Intermediate levels of contribution were found in the three mixed communication conditions. The results are discussed within a theoretical framework that accounts for group decisions and then examines their implications for individual decisions to contribute or not.