'Birds of a feather' - forever? Homogeneity in adult friendship networks through the life course

Networked lives: Probing the influence of social networks on the life course

Social network research is well-equipped to help life course scholars produce a deeper and more nuanced approach to the principle of "linked lives," one of the cornerstones of the field. In this issue on Networked Lives, nine original articles and two commentaries generate new theories, empirical findings and methodological applications at the intersection of the fields of social networks and life course research. In this introduction, we reflect on these advances, highlighting key findings and challenges that await scholars in building more robust synergy between the two fields. Social networks emerge as key structural forces in life courses, yet there is much to learn about the mechanisms through which their effects on people's lives come about. There is a need to study further how networks evolve through the rhythm of life events, and to analyze broader and more complex networks that capture the roles and influences of relations beyond intimate or family ties. These papers demonstrate that there is much to be gained in probing how individuals are linked to and unlinked from others over time, and in carrying conceptual and methodological advances across social network and life course studies.

"Unlinked lives": Elaboration of a concept and its significance for the life course

This article introduces the concept of "unlinked lives" and illustrates its significance for scholarship on the life course. There are many lessons to be learned about human interdependence by focusing not on relationships that are formed and then maintained, but instead on relationships that are lost or ended by choice or circumstance, such as through changes in institutional affiliations, social status and positions or places. Unlinked lives carry important social meanings, are embedded in complex social processes, and bring consequences for the wellbeing of individuals, families, and societies. To develop this concept, we put forward nine key propositions related to when and how unlinkings happen as processes, as well as some of the consequences of being unlinked as a status or outcome. The coupling of "unlinked lives" with "linked lives" offers a crucial avenue for advancing life course theories and research, integrating scholarship across multiple life periods and transitions, and bridging the two now-distinct traditions of intellectual inquiry on the life course and on social networks.

Personal network dynamics across the life course: A relationship-related structural approach

Building on Georg Simmel's concept of "form", the article presents a relationship related structural concept of social relationships that specifically accounts for opportunities and constraints resulting from the fact that relationships are solidified patterns of interaction that, once established, can develop a power of their own (inertia, momentum) that cannot easily be influenced by the involved actors. In this "relationship-related structural approach", social relationships or "forms" can be understood as specific constellations of "basic structural properties", i.e. specifications of various aspects of quantity, of time, of space, of similarity, and including also a certain degree of freedom to enter or quit a relationship, knowledge about one another, and types and degree of institutionalization. The specification of these structural properties impacts the functional capacity of relationships, as well as the dynamics of both relationships and networks, especially the ways in which relationships are formed, maintained, or lost. Referring to various life course transitions from different phases of the life course, it is demonstrated how this approach helps to better understand the dynamics of social relationships and networks and the impact of life events on personal relationships across the life course. Finally, implications of this novel perspective for life course and network research are discussed.

Age integration in the social convoys of young and late midlife adults

Homophily on the basis of age is a notable characteristic of social convoys across the life course. Ties to older and younger persons, therefore, are both unusual and potentially provide unique social support resources. This study examined relationships with older, younger, and same-aged non-kin ties among young and late midlife adults. Data came from the University of California Berkeley Social Networks Study (UCNets), a sample of 485 people aged 21-30 and 674 people aged 50-70. A majority of non-kin ties were to people whose age was within 5 years of the participant's own age, although the majority was much larger for young adults (81 %) than late midlife adults (52 %). Younger and older ties often came from different social settings (school, work, religious organizations, and neighborhoods) than same-aged ties, and there were also some cohort differences in the social settings that produced younger, older, and same-aged ties. Younger and older ties also provided different forms of social support than did ties to same-aged persons. Again, the functions of younger and older ties varied by cohort. Implications for life course studies are discussed.