Network Analysis, History of Philipp Korom, Max Planck Institute for the Study of Societies, Cologne, Germany Ó 2015 Elsevier Ltd. All rights reserved. Abstract While social scientists had been drawing on the abstract idea of social networks clearly since the nineteenth century, which becomes most evident in Georg Simmel’s formal sociology, a social network analysis (SNA) grounded in computational models and graphic imagery emerged within the field of small group research in the 1930s. It was Jacob Moreno who introduced the idea of depicting social structure as a network diagram (‘sociometry’). Kurt Lewin was an early contributor to the promotion of mathematical models of group relations, and Fritz Heider focused on triads to theorize on what throws groups out of balance. Mostly independent of these ideas, the anthropologist Lloyd Warner adopted a network approach in the study of informal relations between workers and of communities. SNA was further applied by the Manchester school of anthropologists to enhance ethnographic description. Advancing mathematical-formal aspects of SNA at Harvard in the 1970s, Harrison C. White and his collaborators contributed to the establishment of the discipline as a recognized paradigm. In the late 1990s, physicists began to publish work on social networks. Today, SNA has become a multidisciplinary research specialty with distinct theoretical concepts and data-analytic techniques. The Origins of Social Network Ideas suggested that a consideration of social dynamics caused by the simple addition of a third person could provide insights on Social structure has been one of the early key concepts in the society at large, that is, how large structures constrain individ- social sciences. Social Network Analysis (SNA) is a recently uals. While isolated dyads are characterized by individuality and developed set of formal methods for the study of social struc- intimacy, triads have a superindividual property: (informal) tures that draws on graph theory in which individuals and social pressures are activated, and the variance of behavior as other social actors, such as groups and organizations, are rep- well as interpersonal idiosyncrasies are reduced. Third-party resented by points and their social relations are represented by effects may also involve two actors forming a coalition against lines. The main theoretical underpinning of SNA is, as Wellman a third, one actor disturbing the alliance between two others, or (1988) pointed out, that the structure of relations among actors one actor even taking advantage of a conflict between two others and the location of individual actors in the network have (‘rejoicing third’). It was Simmel’s student Leopold von Wiese important attitudinal, behavioral, and perceptual conse- (1876–1969) who adopted a contemporary terminology of quences both for individuals and the social structure as points, lines, and connections to describe social relations a whole. Visual imagery has played a significant role in SNA (von Wiese, 1924/1932). since its inception. Mathematical and computational models The origins of structural research are, however, also located are at the base of more current applications. outside the disciplinary boundaries of sociology. Especially the Only in the first part of the twentieth century did a handful work of scholars in educational and developmental of social scientists begin to systematically theorize social rela- psychology, who were interested in the ways small-group tionships. Society as a whole was conceptualized as the very structures affected individual perceptions and actions had tissue of relations. Ferdinand Tönnies (1855–1936) categorized a structuralist flavor very early. Helen Bott, for example, set out social ties as being either personal and direct (‘community’) or to document every form of social interaction that occurred formal and instrumental (‘society’). Herbert Spencer (1820– among preschool children (Bott, 1928). In fact, she was one of 1903) made a similar distinction between premodern and the first to collect ego-centered kinship network data and modern societies by referring to ‘ordinary’ and ‘secondary rela- calculate even network density measures. It is, however, tions.’ Emile Durkheim (1858–1917) theorized the specific commonly agreed that Jacob Moreno, a student of psychiatry structuring of groups as being responsible for the quality of from Vienna who immigrated to the United States in 1925 and emergent laws and morality, and Gustav Le Bon (1841–1931) championed the field of ‘sociometry,’ was the main driving was the first to examine the phenomenon of crowd behavior. It force, together with his collaborator, Helen Jennings, in was, however, Georg Simmel (1858–1918), a German sociol- establishing SNA. ogist whose work stood out against macrolevel theories of Moreno was deeply influenced by Gestalt psychology scholars such as Max Weber (1864–1920) and Karl Marx (Gestalt translates as ‘form’) developed by mostly German (1818–83), who pioneered most explicitly the analysis of dyads psychologists such as Kurt Koffka (1886–1941), Max Wer- (relationships between two persons) and triads (groups theimer (1880–1943), and Wolfgang Köhler (1887–1967) as composed of three people) as building blocks of social life. a protest against behaviorist theories of their day. This school of Although he never used the term ‘social network’ as such, his thought maintained that innate and self-organizing operations ideas about microlevel structures prove to be a source of of the brain influence the way we see. With respect to the visual inspiration even for current day SNA. Simmel held the view that recognition of figures, we tend to perceive, for example, whole sociology was no more and no less than the study of inter- forms instead of just a collection of lines and curves. Moreno weaving actions in social encounters (Simmel, 1908/2009). He transferred the idea that ‘the whole is greater than the sum of its 524 International Encyclopedia of the Social & Behavioral Sciences, 2nd edition, Volume 16 http://dx.doi.org/10.1016/B978-0-08-097086-8.03226-8 Network Analysis, History of 525 parts’ to the interplay between the social embeddedness of an the three (focal individual P, another agent O, object X) can individual and this person’s well-being. He believed that many only exist, if the algebraic multiplication of signs in the triad psychological problems stemmed from failed interactions and relation has a positive value. With three sets of possible rela- that the position of individuals within groups is highly signif- tionships, each taking one of two values ( , ), eight possible þ À icant for their mental health; Moreno and Jennings (1938) thus states exist. A triad is harmonious, for example, if there are two spoke of ‘psychosocial networks.’ Moreno’s concern with social negative and one positive relation (e.g., , , ): “I don’t like À þ À structure is mirrored in therapy forms called ‘sociodrama’ and person B. B has a dog. I don’t like the dog either.” One of ‘psychodrama,’ which aimed at exploring conflicts inherent in Heider’s propositions is that individuals tend to choose states social roles. ‘Sociometry’ was developed as a powerful tool for of balance in their interpersonal relations, which is why the assessing group dynamics and eliciting graphically subjective adages ‘your friends are my friends’ or ‘the enemy of my enemy feelings between persons. Figure 1 illustrates typical ‘socio- is my friend’ adequately summarize core implications of social grams’ featured in the book Who Shall Survive? (Moreno, 1934), balance theory. Building on Lewin’s work, Cartwright and in which Moreno (and Jennings) probed the causes of Harrary translated Heider’s diagrams into graph theory and runaways at the Hudson School for Girls in upstate New York. covered more than triadic relationships by asking the following The crux of their argument was that the location in the social question: What pattern would the interpersonal relations of networks primarily determined whether and when someone a group of individuals have if they were balanced? Important ran away. among their findings is the ‘structure theorem’ that “an s-graph At first, Moreno’s idea to make social structure tangible [signed graph] is balanced if and only if its points can be garnered a great deal of interest, although this turned out to be separated into two mutually exclusive subsets such that each short-lived. By the 1940s, American social scientists had positive line joins two points of the same subset and each returned to their focus on the characteristics of individuals negative line joins points from different subsets” (Cartwright (Freeman, 2004). and Harary, 1956: p. 286; Figure 2). Subsequently, Davis In the 1940s and 1950s, research on social networks (1967) generalized balance to clusterability, which allows advanced on more than one front, mostly independently of any number of clusters such that positive arcs appear within each other. In fact, SNA can be seen as emerging from certain clusters and negative arcs between clusters. Davis and Leinhardt disciplinary trajectories (Prell, 2012), even if scholars working (1972) further extended balance theory by including status, in the field of SNA always crossed disciplines. In the following, which was motivated by the fact that people not only cluster the developmental pathways of SNA are outlined in the key into groups but also adhere to social rankings. They show how disciplines of psychology, sociology, and social anthropology. directed sentiment