Layout Effects: Comparison of Sociogram Drawing Conventions

This report describes a within-subjects experiment in which we compare the relative effectiveness of five sociogram drawing conventions in communicating underlying network substance, based on user task performance and usability preference, in order to examine effects of different spatial layout formats on human sociogram perception. We also explore the impact of edge crossings, a widely accepted readability aesthetic. Subjective data were gathered based on the methodology of Purchase et al. [2002]. Objective data were collected through an online system. We found that both edge crossings and drawing conventions pose significant affects on user preference and task performance of finding groups, but either has little impact on the perception of actor status. On the other hand, the node positioning and angular resolution might be more important in perceiving actor status. In visualising social networks, it is important to note that the techniques that are highly preferred by users do not necessarily lead to best task performance. Introduction A social network [Wikipedia 2005] is a collection of actors (such as people, organizations or other social entities) and relationships among the actors, indicating the way in which they are connected socially (such as friendship, trade or information exchange). Social network analysis is the mapping and measuring of these relationships. This has long been an important technique as well as a popular topic in many academic fields such as Sociology, Social Psychology, and more recently Information Visualization. Social networks can be modelled as graphs, and visualized as node-edge diagrams where nodes represent actors, and edges represent relationships between them. With advances in display media, the use of node-edge diagrams or sociograms (see Figure 1 for an example) has been increasingly important and popular in social network analysis. Sociograms serve as simple visual illustrations in helping people to explore and understand network structure, and to communicate specific information about network characteristics to others. Figure 1: advice network formed by an auditing team. Courtesy of Krackhardt [1996]. Ellipses represent managers; diamonds represent staff auditors and boxes represent secretaries. A line from Donna to Nancy indicates that Donna seeks advice from Nancy. When a social network is mapped to a sociogram, what matters is relationship patterns, not the physical positioning of nodes [Scott 2000, p. 64]. Many network visualization programs such as Pajek [Batagelj et al. 1998], KrackPlot [Krackhardt et al. 1994], or MultiNet [Richards 1999] typically use for example, variants of the spring embedder [Eades 1984], or multidimensional scaling [Kruskal et al. 1978] to determine node positions. However, previous studies [McGrath et al. 1996, 1997] revealed that the