Bridges

A bridge is a line, the removal of which would cause the network to "fall apart" into smaller parts called coherent network components. The figure below shows two bridges: between nodes 1 and 2 and 3 and 4. Breaking any of them would reduce the network's coherence - the network would fall apart into two groups of nodes.

The bridge between 1 and 2 is treated as a bottleneck in the communication process, because it is the only channel for exchanging information between the blue and green groups of vertices. Removing this bridge would cut off the blue vertices from the information "circulating" among the other nodes. In other words, breaking this bridge would create a new coherent component, composed of blue vertices and isolated from the others.

Fig. Bridges in an Example Network

The line between 3 and 4 is also a bridge because if it were removed, node 4 would be isolated and thus create a new connected component of size one node.

Interpreting Bridges in Social Network Analysis: Bridges play a key role as connections between different groups or communities in a network. They enable the flow of information, resources, and influence between nodes that would otherwise be isolated from each other. Individuals or institutions that act as bridges often act as intermediaries, controlling communication between separate parts of the network. They enable the network to function as a whole, despite the existence of subgroups with weak direct connections.

Consequences of the presence of bridges in the network: The presence of bridges increases the susceptibility of the network to disintegration - removing such a connection can lead to the isolation of some nodes and loss of structural coherence. This can hinder the flow of information, limit cooperation and reduce the efficiency of the entire network. On the other hand, people who are bridges gain significant power and influence because they control access to different parts of the network.