View source for Structural cohesion

{{Short description|Lowest number of people removed to disconnect a social group}}

In sociology, '''structural cohesion''' is the conception<ref>
{{cite journal
 |last        = N
 |first       = T
 |author2     = White, Douglas
 |title       = Structural Cohesion and Embeddedness: A Hierarchical Concept of Social Groups.
 |journal     = [[Social:American Sociological Review|American Sociological Review]]
 |volume      = 68
 |issue       = 1
 |pages       = 1–25
 |year        = 2003
 |url         = http://www2.asanet.org/journals/ASRFeb03MoodyWhite.pdf
 |access-date  = 2006-08-19
 |doi         = 10.2307/3088904
 |url-status     = dead
 |archive-url  = https://web.archive.org/web/20060927142539/http://www2.asanet.org/journals/ASRFeb03MoodyWhite.pdf
 |archive-date = 2006-09-27
|jstor       = 3088904
 }}</ref><ref>
{{cite journal
  | last = White
  | first = Douglas
  |author2=Frank Harary 
  | title = The Cohesiveness of Blocks in Social Networks: Node Connectivity and Conditional Density.
  | journal = Sociological Methodology
  | volume = 31
  | issue = 1
  | pages = 305–359
  | year = 2001
  | url = http://eclectic.ss.uci.edu/~drwhite/sm-w23.PDF
  | format = book
  | id =
  | access-date = 2012-08-13
  | doi = 10.1111/0081-1750.00098 | citeseerx = 10.1.1.304.3296
  | s2cid = 15806800
 }}</ref> of a useful formal definition and measure of cohesion in social groups. It is defined as the minimal number of actors in a [[Social:Social network|social network]] that need to be removed to disconnect the group. It is thus identical to the question of the node [[Connectivity (graph theory)|connectivity]] of a given [[Graph (discrete mathematics)|graph]] in [[Discrete mathematics|discrete mathematics]]. The vertex-cut version of [[Menger's theorem]] also proves that the disconnection number is equivalent to a maximally sized group with a network in which every pair of persons has at least this number of separate paths between them. It is also useful to know that {{mvar|k}}-cohesive graphs (or {{mvar|k}}-components) are always a subgraph of a {{mvar|k}}-core, although a {{mvar|k}}-core is not always {{mvar|k}}-cohesive. A {{mvar|k}}-core is simply a subgraph in which all nodes have at least {{mvar|k}} neighbors but it need not even be connected. 

The boundaries of [[Social:Structural endogamy|structural endogamy]] in a kinship group are a special case of structural cohesion.

== Software ==

[https://web.archive.org/web/20080313044932/http://intersci.ss.uci.edu/wiki/index.php/Cohesive_blocking Cohesive.blocking] is the R program for computing structural cohesion according to the Moody-White (2003) [[Algorithm|algorithm]]. This wiki site provides numerous examples and a tutorial for use with R.

== Examples ==
Some illustrative examples are presented in the gallery below:

<gallery>
Image:RingNetwork.svg|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.

Image:6n-graf.svg|The 6-node component (1-connected) has an embedded 2-component, nodes 1-5

Image:NetworkTopology-FullyConnected.png|A 6-node clique is a 5-component, structural cohesion 5
</gallery>

== 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.<ref>Chin, Wynne W., et al. [http://sgr.sagepub.com/cgi/content/abstract/30/6/751 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.</ref>

== See also ==
* [[Social:Community cohesion|Community cohesion]]
* Social cohesion
* [[Social:Social network|Social network]]

== References ==
{{Reflist}}

{{Social networking}}

[[Category:Graph connectivity]]
[[Category:Network analysis]]
[[Category:Sociological terminology]]

{{Sourceattribution|Structural cohesion}}