John Skvoretz

The evolution of trust and cooperation between strangers: A computational model.

Social and economic exchanges often occur between strangers who cannot rely on past behavior or the prospect of future interactions to establish mutual trust. Game theorists formalize this problem as a one-shot prisoners dilemma and predict mutual noncooperation. Recent studies, however, challenge this conclusion. If the game provides an option to exit (or to refuse to play), strategies based on projection (of a players intentions) and detection (of the intentions of a stranger) can confer a cooperators advantage. Yet previous research has not found a way for these strategies to evolve from a random start or to recover from invasion by aggressive strategies that feign trustworthiness. The authors use computer simulation to show how trust and cooperation between strangers can evolve without formal or informal social controls. The outcome decisively depends, however, on two structural conditions : the payoff for refusing to play, and the embeddedness of interaction. Effective norms for trusting strangers emerge locally, in exchanges between neighbors, and then diffuse through weak ties to outsiders

EXCLUSION AND POWER: A TEST OF FOUR THEORIES OF POWER IN EXCHANGE NETWORKS*

We evaluate four theories that predict the distribution of power in exchange networks. All four theories-core theory, equidependence theory, exchange-resistance theory, and expected value theory-assume actors rationally pursue self-interests. Three of the theories add social psychological assumptions that place the pursuit of self interest in an interactive context. Predictions of exchange earnings by the four theories are evaluated against data from eight experimental networks, including types of networks not previously studied. These networks vary conditions that affect the chances that a position can be excluded from exchange. We find that when the theories base predictions on a network positions structural potential for exclusion, exchange-resistance theory provides the bestfit, but when predictions are based on actual experiences of exclusion, expected value theory fits best. Our discussion focuses on the distinction between the a priori potential for exclusion versus experienced exclusion as factors in the genesis of power T he problem of power distribution in exchange networks has captured the attention of a variety of theorists. The appeal of the problem derives from the combination of the formal representation of social structure as network (Wellman and Berkowitz 1992) and sociologys perennial concern with power. A growing body of experimental studies now permits researchers to test various theoretical formulations. How does location in a network confer advantages on a person or a corporate body in their dealings with others? Consider the promotion prospects of two senior accountants, Andy and Bob. Because Andys work involves accounts at various regional offices, his coworkers typically do not know each other. Bob, on the other hand, deals with corporate accounts, so his coworkers typically associate with each other. Thus, Andy and Bob are surrounded by two very different networks and it is not obvious that Andys network favors him for promotion (Burt 1992). In a second ex

Comparing Networks Across Space and Time, Size and Species

We describe and illustrate methodology for comparing networks from diverse settings. Our empirical base consists of 42 networks from four kinds of species (humans, nonhuman primates, nonprimate mammals, and birds) and covering distinct types of relations such as influence, grooming, and agonistic encounters. The general problem is to determine whether networks are similarly structured despite their surface differences. The methodology we propose is generally applicable to the characterization and comparison of network-level social structures across multiple settings, such as different organizations, communities, or social groups, and to the examination of sources of variability in network structure. We first fit a p* model (Wasserman and Pattison 1996) to each network to obtain estimates for effects of six structural properties on the probability of the graph. We then calculate predicted tie probabilities for each network, using both its own parameter estimates and the estimates from every other network in the collection. Comparison is based on the similarity between sets of predicted tie probabilities. We then use correspondence analysis to represent the similarities among all 42 networks and interpret the resulting configuration using information about the species and relations involved. Results show that similarities among the networks are due more to the kind of relation than to the kind of animal.

Salience, Heterogeneity and Consolidation of Parameters: Civilizing Blau's Primitive Theory

Blaus (1977) theory uses properties of macro social structure to deduce properties of micro social structure, the network of observed social relations among individuals. This paper continues the work of Fararo (1981) in providing a formal linkage between these two levels using the concepts of biased net theory. The application provides versions of Blaus major theorems that uncover implications not readily apparent from his verbal presentation, permits the extension of his theory beyond characteristics along which preferences for ingroup association exist to ones along which preferences for outgroup association may exist (and ones even stranger where both preference types may exist), demonstrates the theoretical basis for some negative results of recent research (Blau et al., 1982), and offers a rigorous basis for a general formal theory of-social structures influences on peoples associations with one another.

Institutions as production systems

This paper proposes a formal mode of representation and a corresponding way of thinking about institutionalized social action. It draws its representational technique and its way of thinking about its subject from several sources, including systems theory, cognitive science, and structuralism. It is based on the idea that a model involves a proposed generative mechanism for observable patterns of action and that such a generator must be a system of rules. We discuss the philosophical and sociological presuppositions of our proposal, then outline in detail and illustrate the idea of a production system model. Following this, we argue that the proposed mode of representation is appropriate for “the action frame of reference” and then develop a series of specific “problematics” involving the structural analysis of institutionalized social action. We conclude with a discussion of issues and problems for further research. The paper does not include mathematical work found elsewhere, although it tries to indica...

Diversity, Integration, and Social Ties: Attraction versus Repulsion as Drivers of Intra- and Intergroup Relations1

Interethnic and intergroup social ties are critical to knitting together increasingly diverse societies into cohesive wholes. Yet their formation faces the homophily hurdle: important and intimate social ties tend to be established disproportionately between those sharing significant social attributes. In the spirit of analytical sociology, the author explores two mechanisms that could drive intra- and intergroup relations: attraction to similar versus repulsion from dissimilar others. The models differ in predictions as illustrated by data on interethnic marriages in Great Britain and the United States, on U.S. dating and cohabitation relations by religion and education, on educational diversity in marriages in 22 European countries, and on marriages of the native and foreign-born in Austria. A unified model for the two mechanisms, in which tie formation is a conceptualized as a two-stage process of encounter and consummation, is proposed, and its empirical and theoretical analysis provides deeper understanding of the homophily hurdle.

Advances in biased net theory: definitions, derivations, and estimations

Abstract Random and biased net theory, introduced by Rapoport and others in the 1950s, is one of the earliest approaches to the formal modeling of social networks. In this theory, intended as a theory of large-scale networks, ties between nodes derive both from random and non-random events of connection. The non-random connections are postulated to arise through “bias” events that incorporate known or suspected systematic tendencies in tie formation, such as, mutuality or reciprocity, transitivity or closure in triads, and homophily—the overrepresentation of ties between persons who share important socio-demographic attributes like race/ethnicity or level of educational attainment. A key problem for biased net theory has been analytical intractability of the models. Formal derivations require approximation assumptions and model parameters have been difficult to estimate. The accuracy of the derived formulas and the estimated parameters has been difficult to assess. In this paper, we attempt to address long-standing issues in biased net models stemming from their analytical intractability. We first reformulate and clarify the definitions of basic biases. Second, we derive from first principles the triad distribution in a biased net, using two different analytical strategies to check our derivations. Third, we set out a pseudo-likelihood method for parameter estimation of key bias parameters and then check the accuracy of this relatively simple but approximate scheme against the results obtained from the triad distribution derivation.

Power in exchange networks : setting and structural variations

This article adds to the body of findings on how network position and the conditions of exchange influence an actors power to obtain favorable outcomes. Four network structures of four persons each are examined in each of two experimental settings: a face-to-face setting, in which negotiations are carried out directly, and the ExNet setting, in which negotiations are carried out through a microcomputer-based electronic network. The structures are selected to provide further tests of the Markovsky et al. s (1988) procedure for locating power positions. The different settings allow an assessment of the scope of their analysis. The results generally support their predictions. Also examined are two types of predictions, contingency and value, derived from the operant basis of Emersons (1969) power-dependence theory. The contingency predictions receive more support than do the value predictions.

Biased networks and social structure theorems: Part II

It was shown in a previous paper (Fararo 1981) that the part of Peter Blaus theory of social structure bearing on heterogeneity could be embedded within the framework of biased net models, providing a conceptual and mathematical basis for its central theorems. This paper continues this project. It begins by indicating certain revisions of the earlier work and then turns to the part of Blaus theory that deals with inequality and shows how the simplest inbreeding bias model, through a series of derivations and constructive generalizations, permits the derivation of basic theorems that relate the Gini inequality (of a population) to what we term the relational Gini (of a network). The central idea is to construct theoretical models that yield specific forms of transformation of the population Gini into the relational Gini.

Models of participation in status-differentiated groups.

Several models of participation in status-differentiated groups are proposed, and their fit is examined with data from 31 six-person discussion groups which vary systematically in sex composition from entirely male to entirely female. The six models share a common framework in which participation is viewed as the outcome of two processes: first, a process by which chances to participate are channeled to group members, and second, a process by which chances are taken (or not) by the group members to whom they are allocated. The models differ at the level of specific assumptions about these processes: for example, in the baseline model chances are allocated equally to group members and each member has the same likelihood of taking a chance to which he or she is exposed. The best-fitting models are the basic hierarchy model first proposed by Horvath and a variant of this model in which higher-status actors are more likely than lower-status actors to take chances to which they are exposed. Neither model, however, provides completely satisfactory accounts of the data, suggesting the need for further study of how status differentiation affects participation in small-group task-oriented discussions.