Introduction to social network analysis Introduction to social network analysis Paola Tubaro University of Greenwich, London 27th June 2012 Introduction to social network analysis Introduction Welcome! Rise of online social networking services: ⇒ social networks to the fore. New interest for social network analysis (SNA). Yet networks have always existed! Likewise, SNA now has a long history. Introduction to social network analysis Introduction This workshop Understand what SNA is. Understand how you could use it. Learn basic principles and measures. Be aware of available resources. Introduction to social network analysis Introduction Outline Outline 1 Introduction 2 What is SNA 3 Data 4 Network metrics 5 Models 6 Resources Introduction to social network analysis Introduction Motivation What can SNA be used for? Classical applications: Improvements in organisational performance. Social policy interventions for behaviour change; Newer applications on online social networking services: For organisations; For social policy. Introduction to social network analysis Introduction Motivation The organisational chain of a company Introduction to social network analysis Introduction Motivation Formal chart vs. network With whom do you discuss issues important to your work? Introduction to social network analysis Introduction Motivation Formal chart vs. network With whom do you discuss issues important to your work? Senior people relatively peripheral (Barry): removed from day-to-day activities of the group. Introduction to social network analysis Introduction Motivation Formal chart vs. network With whom do you discuss issues important to your work? The very central role of Nick (what if he moves to another job?) Introduction to social network analysis Introduction Motivation Formal chart vs. network With whom do you discuss issues important to your work? Product 1 division relatively separate from overall network. Introduction to social network analysis Introduction Motivation Interventions Using network data to improve flows of communication and coordination in the organisation. Introduction to social network analysis Introduction Motivation Networks for behaviour change: smoking prevention Network of friendships among sixth grade pupils. Squares = girls, circles = boys; blue = smokers, red = non-smokers. Valente et al. 2003. Introduction to social network analysis Introduction Motivation Use popular pupils (“opinion leaders”) to reduce smoking in adolescents Identify most popular pupils in class; Recruit and train them; Use them to spread the message. Valente et al. 2003: network method effective in reducing adolescents’ smoking. Introduction to social network analysis What is SNA Defining SNA An approach to human behaviours and social interactions. A set of specific analytical and statistical methods. A special type of data (and techniques of data collection). A set of visualisation tools. ⇒ It applies to both online and offline social networks. ⇒ It can be combined with other social science theories, methods and data. Introduction to social network analysis What is SNA What is a network What is a network —a formal definition = A set of units (nodes) connected by one or more relations (ties) What is a node? ⇒ Depends on setting: person, group/organisation, object. What is a tie? ⇒ A relation or a shared trait: friendship, advice, exchange, co-work. Introduction to social network analysis What is SNA What is a network Graphs and networks Circles (A,B) represent nodes. Lines (e.g. betweenA andB) represent ties/edges. Graph visualizes the whole structure of ties of a defined group. Graphical conventions (colours, size of nodes and/or ties) can be added to show attributes. For example: if this is a network of friendship, blue = boys, red = girls. Introduction to social network analysis What is SNA What is a network Graphs and networks Circles (A,B) represent nodes. Lines (e.g. betweenA andB) represent ties/edges. Graph visualizes the whole structure of ties of a defined group. Graphical conventions (colours, size of nodes and/or ties) can be added to show attributes. For example: if this is a network of friendship, blue = boys, red = girls. Introduction to social network analysis What is SNA What is a network Isolates, dyads and triads a b c ¡A u u ¡ uA ¡ A ¡ A ¡ A d e ¡ A f u u u Isolate Dyad Triad Introduction to social network analysis What is SNA The network perspective A new perspective SNA requires a change of mindset with respect to other social science approaches. Emphasis is on relationships, not attributes. Not just dyadic relationships (just A and B), but dyadic relationships as embedded in a whole set of relationships. Introduction to social network analysis What is SNA The network perspective A new perspective SNA requires a change of mindset with respect to other social science approaches. Emphasis is on relationships, not attributes. Not just dyadic relationships (just A and B), but dyadic relationships as embedded in a whole set of relationships. Introduction to social network analysis What is SNA The network perspective A new perspective SNA requires a change of mindset with respect to other social science approaches. Emphasis is on relationships, not attributes. Not just dyadic relationships (just A and B), but dyadic relationships as embedded in a whole set of relationships. Introduction to social network analysis What is SNA The network perspective Embedded relationships Figure: Suppose the relationship represented here is friendship. How may friendship between A and B vary in these three different contexts? Introduction to social network analysis What is SNA The network perspective Triads a a a ¡A ¡A ¡AK ¡ uA ¡ uA ¡ uA ¡ A ¡ A ¡ A ¡ A ¡ A ¡ A ¡ A ¡ A ¡ A b ¡ AU c b ¡ -AU c b ¡ -A c u u u u u u Intransitive Transitive 3-cycles Intransitive: Only bilateral ties. Transitive: A friend of my friend is my friend. Three-cycles: a form of generalized exchange. Introduction to social network analysis What is SNA The network perspective Triads a a a ¡A ¡A ¡AK ¡ uA ¡ uA ¡ uA ¡ A ¡ A ¡ A ¡ A ¡ A ¡ A ¡ A ¡ A ¡ A b ¡ AU c b ¡ -AU c b ¡ -A c u u u u u u Intransitive Transitive 3-cycles Intransitive: Only bilateral ties. Transitive: A friend of my friend is my friend. Three-cycles: a form of generalized exchange. Introduction to social network analysis What is SNA The network perspective Some theory Georg Simmel: triad as a fundamental unit of sociological analysis. Three actors in a triad may allow for social dynamics that are qualitatively different from what can be observed based on dyads or individuals. Social behaviours and phenomena cannot be reduced to dyads or individuals. The right starting point is the triad (and higher). N.B. Dyad = a two-nodes set; Triad = a three-node set. Introduction to social network analysis What is SNA The network perspective Network effects, more globally a 1 ¡ AK e ¡ xA ¡ A x ¡ A d ¡ A xb ¡ A c x x For example, those who attract many choices will attract even more in future (reputation effect, “Matthew” effect). Introduction to social network analysis What is SNA The network perspective Network effects, more globally a 1 ¡ AK e ¡ xA ¡ A x ¡ A d ¡ A xb ¡ A c x x For example, those who attract many choices will attract even more in future (reputation effect, “Matthew” effect). Introduction to social network analysis What is SNA The network perspective Network effects, more globally a 1 ¡ AK e ¡ xA ¡ A x ¡ A d ¡ A xb ¡ A c x x For example, those who attract many choices will attract even more in future (reputation effect, “Matthew” effect). Introduction to social network analysis What is SNA The network perspective Network effects, more globally a 1 ¡ AK e ¡ xA ¡ A x ¡ A d ¡ A xb ¡ A c x x For example, those who attract many choices will attract even more in future (reputation effect, “Matthew” effect). Introduction to social network analysis What is SNA The network perspective The importance of network position Position in network determines a opportunities and constraints; 1 e ¡ AK ¡ xA For example a is very central, and ¡ A will become ever more central over x ¡ A time; d ¡ A x ¡ A Does a high (and rising) number of b c friends have advantages? x x Does it have disadvantages? In this respect, how does a compare to b (or c or d)? Introduction to social network analysis What is SNA The network perspective More precisely, what are constraints and opportunities? Burt 1992, 2005, 2010, in a business context: Closure: every member of a network is (directly or indirectly) connected to everyone else. Communication reinforces shared views. Strengthens social control. Imposes reputation costs on any poor behavior. Facilitates trust formation. May be a source of rigidity (redundant information). Introduction to social network analysis What is SNA The network perspective Constraints and opportunities (cont.) Burt’s “structural holes”: Broker (A) bridges groups that are otherwise little connected. Can access knowledge and information from different sources (groups 1 and 2). Facilitates innovation through flows of information and knowledge between groups. Competitive advantage. Introduction to social network analysis What is SNA The network perspective Weak ties and information Granovetter’s classical thesis (1973): Weak ties act as bridges; Through weak ties, individuals have better access to non-redundant information; This is one reason why weak ties are often instrumental in finding jobs. Introduction to social network analysis What is SNA The network perspective Networks and groups Some social science concepts or objects can be re-interpreted as networks. For example: Collectivities perceived as groups are often better described as networks. Notion of group only allows for binary membership status, while network considers varied levels of embeddedness and commitment; A group appears as a cohesive whole, while a network allows for multiple memberships and interests (whether in agreement or conflict). Adapted from: Marin 2011. Introduction to social network analysis What is SNA The network perspective Network position and attributes Traditional social science places emphasis on individuals’ attributes (gender, age, education, occupation etc.).