This book illustrates an important moment in social network analysis: the continued maturation of the field into a truly interdisciplinary science. The chapters represent the disciplines of anthropology, applied mathematics and statistics, communications research, demography, industrial engineering, management, political science, social psychology, and sociology.

The chapters also represent the continued maturation of social network analysis into a truly “normal science,” in Thomas Kuhn’s (1996:10) memorable phrase. In 1977, Samuel Leinhardt edited a volume titled Social Networks: A Developing Paradigm. The book had papers from social psychology, sociology, statistics and mathematics, and anthropology – the range of disciplines that, in 1977, was coalescing into what Leinhardt called a developing paradigm – that is, a normal science. Leinhardt was right. In 1993, Norman Hummon and Kathleen Carley analyzed the contents of the i rst 12 years of the journal Social Networks (1978–1989). The pattern of citations, they said, indicated the development of a normal science: The field was incremental (people “attend to each other’s work”) and there were “young scientists willing to base their careers on work in this i eld,” suggesting that “social networks as a specialty is in a ‘normal science’ phase rather than an early developmental phase” (pp. 103–04).

One characteristic of a normal science is the easy, unpretentious use of qualitative and quantitative data and analysis. This is the salutary result of the mixed methods movement. I use the word “movement” deliberately. As of April 2012, there were 2,100 citations to the term “mixed methods” in the Social Science Citation Index. As shown in the figure, the first occurrence of the term dates from 1993, with more than 80 percent since 2008. There is a Journal of Mixed Methods Research (mmr.sagepub.com), several textbooks on mixed methods research (Creswell and Plano Clark 2011; Greene 2007; Hesse-Biber 2010; Morse and Niehaus 2009), and a handbook of mixed methods research (Tashakkori and Teddlie 2010). What else could this possibly be if not a movement?