The source nexus of influence has long been attributed to social groups. Cooley (1962, 1909) defined the primary group by intimate face-to-face association and cooperation, which he considered as foundational for the creation of an individual’s ideals and social nature. A century ago he argued that the very self is constituted by the shared life and purposes of the primary group. More recently, Athens (1992) has elaborated and clarified the definition of the primary group as the following:

These and other sociologists have long observed that the primary group – far more than the secondary – has great impact on the development of values, repertoires, and identity of the individual. That there may be more than one highly influential group renders the primary label less useful; in these and other ways the dynamics of influential social groups (both in their creation and functioning) can now be more elaborately described. Thus I will refer to these influential groups as psychosocial systems.