Structural cohesion

Structural cohesion is the sociological conception ^[1][2] of cohesion in social groups. It is defined as the minimal number of actors in a social network that need to be removed to disconnect at least two actors in the remaining group. It is thus identical to the question of the node connectivity of a given graph. The solution to the boundary problem for structural cohesion, i.e., the question whether there is a single actor that acts as a bridge between two groups, is thus found by the vertex-cut version of Menger's theorem. The boundaries of structural endogamy are a special case of structural cohesion. It is also useful to know that k-cohesive graphs (or k-components) are always a subgraph of a k-core, although a k-core is not always k-cohesive. A k-core is simply a subgraph in which all nodes have at least k neighbors but it need not even be connected.

Software

Cohesive.blocking is the R program for computing structural cohesion according to the Moody-White (2003) algorithm. This wiki site provides numerous examples and a tutorial for use with R.

Examples

Some illustrative examples are presented in the gallery below:

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  The 6-node ring in the graph has connectivity-2 or a level 2 of structural cohesion because the removal of two nodes is needed to disconnect it.

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  The 6-node component (1-connected) has an embedded 2-component, nodes 1-5

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  A 6-node clique is a 5-component, structural cohesion 5

Perceived cohesion

Perceived Cohesion Scale (PCS) is a six item scale that is used to measure structural cohesion in groups. In 1990, Bollen and Hoyle used the PCS and applied it to a study of large groups which were used to assess the psychometric qualities of their scale.^[3]

See also

• Community cohesion
• Social cohesion
• Social network
• Social-circles network model

References

1. ^ Moody, James; White, Douglas (2003). "Structural Cohesion and Embeddedness: A Hierarchical Concept of Social Groups." (PDF). American Sociological Review 68 (1): 1–25. http://www2.asanet.org/journals/ASRFeb03MoodyWhite.pdf. Retrieved 2006-08-19. 
2. ^ White, Douglas; Frank Harary (2001). "The Cohesiveness of Blocks in Social Networks: Node Connectivity and Conditional Density." (book). Sociological Methodology 2001 (Blackwell Publishers, Inc., Boston, USA and Oxford, UK.) 31 (1): 305–359. doi:10.1111/0081-1750.00098. http://www.ingentaconnect.com/content/bpl/some/2001/00000031/00000001/art00098;jsessionid=1f96pkuejdhry.victoria. Retrieved 2006-08-19. ^{[dead link]}
3. ^ Chin, Wynne W., et al. Perceived Cohesion: A Conceptual and Empirical Examination: Adapting and Testing the Perceived Cohesion Scale in a Small-Group Setting. 1999. Small Group Research 30(6):751-766.