Chapter 1 A group can be defined by an attribute for example women democrats lawyers or as a specific collection of individuals to whom we can literally point those people right over there A social network like a group is a collection of people it includes something more a specific set of connections between people in the group These ties and the particular pattern of these ties are often more important than the individual people themselves A social network is an organized set of people that consists of two kinds of elements human beings and the connections between them Real everyday social networks evolve organically from the natural tendency of each person to seek out and make many or few friends to have large or small families to work in personable or anonymous workplaces A network s shape also known as its structure or topology is a basic property of the When a group is constituted as a network there is a particular pattern of ties that connects the network people involved the topology There are two fundamental aspects of social networks whether they re simple or complex 1 connection which has to do with who is connected to whom 2 contagion which pertains to what if anything flows across the ties Understanding why social networks exist and how they work requires that we understand certain rules regarding connection and contagion the structure and function of social networks Rule 1 We shape our network Humans deliberately make and remake their social networks all the time ex homophily the conscious or unconscious tendency to associate with people who resemble us We choose he structure of our networks in three important ways 1 we decide how many people we are connected to 2 we influence how densely interconnected our friends and family are 3 we control how central we are to the social network If you know Alexi and Alexi knows Lucas and Lucas knows you this relationship is transitive the three people involved form a triangle Those with high transitivity are usually deeply embedded within a single group while those with low transitivity tend to make contact with people from several different groups who do not know one another making them more likely to act as a bridge between different groups Rule 2 Our Network Shapes Us Our place in the network affects us in turn Whether your friends and other social contacts are friends with one another is crucial to your experience of life Transitivity can affect everything from whether you find a sexual partner to whether you commit suicide How many contacts your friends and family have is also relevant When the people you are connected to become better connected it reduces the number of hops you have to take from person to person to reach everyone else in the network You become more central Being more central makes you more susceptible to whatever is flowing within the network Rule 3 Our friends Affect Us What actually flows across the connections is crucial in addition the shape One fundamental determinant of flow is the tendency of human beings to influence and copy one another The simple tendency for one person to influence another has tremendous consequences when we look beyond our immediate connections Rule 4 Our Friends Friends Friends Affect Us People copy their friends friends and their friends friends friends Hyperdyadic spread or the tendency of effects to spread from person to person to person beyond an individual s direct social ties To observe hyperdyadic spread 1 observe entire network 2 Get information about the ties and the people they connect at more than one time otherwise we have no hope of understanding the dynamic properties of the network Rule 5 The Network Has a Life of Its Own Social networks can have properties and functions that are neither controlled nor even perceived by the people within them These properties can be understood only by studying the whole group and its structure not by studying isolated individuals culture traffic jams An excitable medium is one that flips from one state to another depending on what others around it are doing Social networks have emergent properties new attributes of a whole that arise from interaction and interconnection of the parts Six degrees of Separation and Three Degrees of influence People are all connected to one another by an average of six degrees of separation Milgram Intrinsic decay explanation our affect dies off after three degrees of influence Network instability explanation links beyond three degrees are unstable people die divorce happens Evolutionary purpose explanation evolutionary biology humans appear to have to have evolved in small groups in which everyone would have been connected to everyone else by three degrees or less In our hominid past there was no one who was four degrees removed from us No matter the reasons the Three Degrees Rule appears to be an important part of the way human social networks function and it may continue to constrain our ability to connect even though technology give us access to many more people Connection and contagion are the structure and function of social networks Connected Social networks have value precisely because they can help us to achieve what we could not achieve on our own Social networks can dramatically reinforce two different kinds of inequality in our society 1 situational inequality some are better off socioeconomically 2 positional inequality some are better off in terms of where they are located in the network Social networks provides a distinct way of seeing the world b c it is about individuals and groups and about how the former actually become the latter Chapter 2 Our Ancestors Had Feelings The development of emotions in humans the display of emotions and the ability to read the emotions of others helped coordinate group activity by three means facilitating interpersonal bonds synchronizing behavior and communicating information Emotional contagion fosters interaction synchrony Emotional Contagion Emotions spread form person to person b c 2 features of human interaction we are biologically hardwired to mimic others outwardly and in mimicking their outwardly displays we come to adopt their inward states Prosopagnosia losing the ability to read facial expressions People imitate the facial expressions of others as a result they come to feel as they do affective afference or the facial feedback theory A biological reason emotions may be contagious mirror neuron system Emotional Stampedes When emotions