Social Networks 40 (2015) 90–102 Contents lists available at ScienceDirect Social Networks jo u r n al hom ep age: www.elsevier.com/locat e/socnet How stable is the core discussion network? Mario Luis Small a,* , Vontrese Deeds Pamphile b , Peter McMahan c a Harvard University, United States b Northwestern University, United States c University of Chicago, United States a r t i c l e i n f o Keywords: Core discussion network Network evolution Strong ties Opportunities Obligations Routines a b s t r a c t Researchers have paid increasing attention to the core discussion network, the set of people we turn to when discussing important matters. Because the core discussion network is theorized to be composed of people’s closest ties, not fleeting acquaintances, it is expected to be largely stable, evolving slowly over the span of people’s lives. However, recent studies have shown that networks are strongly affected by the contexts in which people interact with others, and as people experience life course transitions, they also often enter new contexts – school, college, work, marriage, and retirement. We ask whether, as actors enter new social contexts, the core discussion network remains stable or changes rapidly. Based on original, longitudinal, qualitative and quantitative data on the experience of first-year graduate students in three academic departments in a large university, we examine the stability of the core discussion network over the first 6 and 12 months in this new context. We test four competing hypotheses that focus on strength of ties, new opportunities, obligations, and routine activity and predict, respectively, stasis, expansion, shedding, and substitution. We find that the core discussion network changes remarkably quickly, with little or no lag, and that it appears to do so because both the obligations that people face and the routine activities they engage in are transformed by new institutional environments. Findings suggest that core discussion network may be less a “core” network than a highly contextual support network in which people are added and dropped as actors shift from environment to environment. © 2014 Elsevier B.V. All rights reserved. 1. Introduction One of the most important networks studied in recent years has been the core discussion network, the set of people an individual regularly turns to when he or she has important matters to discuss (Marsden, 1987; McPherson et al., 2006; McPherson, 2009; Fischer, 2009; Brashears, 2011; Paik and Sanchagrin, 2012; Small, 2013). The core discussion network is theorized to be a major source of support over the span of a person’s life, and it represents one of the most important ways that social networks are said to bene- fit everyday well-being (Fischer, 1982a,b; Marsden, 1987). When social scientists have sought to understand changes in the social networks of Americans over the past several decades, they have focused on changes in the core discussion network (McPherson et al., 2006; McPherson, 2009). And when they have sought to understand large-scale patterns in the nature of social support or the prevalence of isolation both in the U.S. and in other countries, * Corresponding author at: 33 Kirkland St., William James Hall, Department of Sociology, Cambridge, MA 02137, United States. Tel.: +1 617 496 7778. E-mail address: mariosmall@fas.harvard.edu (M.L. Small). they have turned to the core discussion network as well (Marsden, 1987; Ruan, 1998; Völker and Flap, 2002; Suzman, 2009; Brashears, 2011). As all networks are, the core discussion network is dynamic. Yet while several studies have focused on how the core discus- sion network has changed over a generation in American society (McPherson et al., 2006; McPherson, 2009; Fischer, 2009), few have examined how the core discussion network changes over the life of an individual. For example, we know that the core discussion net- work tends to be slightly smaller in the later years (see Cornwell et al., 2008; see also McDonald and Mair, 2010; Kalmijn, 2012). Yet we know little about its stability in size or composition at other stages in life, such as when people enter school, begin their first jobs, or marry. As a result, we know surprisingly little about how dynamic or stable this important form of social support is. The extent to which the core discussion network remains sta- ble in life transitions becomes an especially intriguing question when we consider the many recent studies suggesting that per- sonal networks are sensitive to social contexts (Hsung et al., 2009; Small, 2009; Conti and Doreian, 2010; Doreian and Conti, 2012; Mollenhorst et al., 2014). A number of classic and recent studies have shown that the physical and institutional contexts of social http://dx.doi.org/10.1016/j.socnet.2014.09.001 0378-8733/© 2014 Elsevier B.V. All rights reserved.