Analysis of social networks is suggested as a tool for linking micro and macro levels of sociological theory. The procedure is illustrated by elaboration of the macro implications of one aspect of small-scale interaction: the strength of dyadic ties. It is argued that the degree of overlap of two individuals' friendship networks varies directly with the strength of their tie to one another. The impact of this principle on diffusion of influence and information, mobility opportunity, and community organization is explored. Stress is laid on the cohesive power of weak ties. Most network models deal, implicitly, with strong ties, thus confining their applicability to small, well-defined groups. Emphasis on weak ties lends itself to discussion of relations between groups and to analysis of segments of social structure not easily defined in terms of primary groups.

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The Strength of Weak Ties

In this paper, the concept of social capital is introduced and illustrated, its forms are described, the social structural conditions under which it arises are examined, and it is used in an analys...

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Social Capital in the Creation of Human Capital

The emergence of order in natural systems is a constant source of inspiration for both physical and biological sciences. While the spatial order characterizing for example the crystals has been the basis of many advances in contemporary physics, most complex systems in nature do not offer such high degree of order. Many of these systems form complex networks whose nodes are the elements of the system and edges represent the interactions between them. 
Traditionally complex networks have been described by the random graph theory founded in 1959 by Paul Erdohs and Alfred Renyi. One of the defining features of random graphs is that they are statistically homogeneous, and their degree distribution (characterizing the spread in the number of edges starting from a node) is a Poisson distribution. In contrast, recent empirical studies, including the work of our group, indicate that the topology of real networks is much richer than that of random graphs. In particular, the degree distribution of real networks is a power-law, indicating a heterogeneous topology in which the majority of the nodes have a small degree, but there is a significant fraction of highly connected nodes that play an important role in the connectivity of the network. 
The scale-free topology of real networks has very important consequences on their functioning. For example, we have discovered that scale-free networks are extremely resilient to the random disruption of their nodes. On the other hand, the selective removal of the nodes with highest degree induces a rapid breakdown of the network to isolated subparts that cannot communicate with each other. 
The non-trivial scaling of the degree distribution of real networks is also an indication of their assembly and evolution. Indeed, our modeling studies have shown us that there are general principles governing the evolution of networks. Most networks start from a small seed and grow by the addition of new nodes which attach to the nodes already in the system. This process obeys preferential attachment: the new nodes are more likely to connect to nodes with already high degree. We have proposed a simple model based on these two principles wich was able to reproduce the power-law degree distribution of real networks. Perhaps even more importantly, this model paved the way to a new paradigm of network modeling, trying to capture the evolution of networks, not just their static topology.

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Statistical mechanics of complex networks

Scholars in various disciplines have considered the causes, nature, and effects of trust. Prior approaches to studying trust are considered, including characteristics of the trustor, the trustee, and the role of risk. A definition of trust and a model of its antecedents and outcomes are presented, which integrate research from multiple disciplines and differentiate trust from similar constructs. Several research propositions based on the model are presented.

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An Integrative Model Of Organizational Trust

Similarity breeds connection. This principle—the homophily principle—structures network ties of every type, including marriage, friendship, work, advice, support, information transfer, exchange, comembership, and other types of relationship. The result is that people's personal networks are homogeneous with regard to many sociodemographic, behavioral, and intrapersonal characteristics. Homophily limits people's social worlds in a way that has powerful implications for the information they receive, the attitudes they form, and the interactions they experience. Homophily in race and ethnicity creates the strongest divides in our personal environments, with age, religion, education, occupation, and gender following in roughly that order. Geographic propinquity, families, organizations, and isomorphic positions in social systems all create contexts in which homophilous relations form. Ties between nonsimilar individuals also dissolve at a higher rate, which sets the stage for the formation of niches (localize...

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Birds of a Feather: Homophily in Social Networks

Suggests a new approach to describing both stability and change in social systems by linking the behavior of individuals to organizational behavior.

Foundations of Social Theory

(1968). EQUALITY OF EDUCATIONAL OPPORTUNITY. Equity & Excellence in Education: Vol. 6, No. 5, pp. 19-28.

Equality of Educational Opportunity

Equality of Educational Opportunity.

Introduces and illustrates the concept of social capital, describes its forms, and examines the social structures in which it arises. An application of the concept is used in analyzing high school dropouts. The theory is set in the context of rational action, with sociological and economic explanations (both of which are criticized and revised). Social capital as a resource for action is a way of importing the principle of rational action in the analysis of social systems, including economic systems. Social capital is a particular kind of resource available to an actor. Although not completely fungible, it is productive and makes achievement of ends possible. It inheres in the structure of relations between and among actors. It also shares features with public goods (in that it benefits all who are part of the structure). Social capital is employed in the creation of human capital, which is created by changes in persons that create skills and capabilities that enable them to act in new ways. It is especially important in creating human capital in the next generation. Social capital is one of three components (along with financial capital and human capital) in family background. An application of the concept of social capital is undertaken by examining the effect of its lack in high school sophomores on their drop-out rate. The study draws on the data in the High School and Beyond dataset. Various analyses show that social capital in the family is an educational resource of children, just as are the family's financial and social capital. For example, frequent family moves disrupt the family's social capital, and each move increases the child's dropout rate. Low drop out rates at Catholic and private schools are also indicators of a child's social capital outside the school. (TNM)

James S. Coleman

Papers

Social Capital in the Creation of Human Capital

Foundations of Social Theory

Equality of Educational Opportunity

Equality of Educational Opportunity.

Social Capital in the Creation of Human Capital