ConnectedPreface• Nicholas Christakis & James Fowler• fundamental rules that govern both the formation and operation of social networksChapter 1: In the Thick of It• epidemics of violence - a single murder can set off a cascade of killings• 75% of all homicides involve people who knew each other, often intimately, prior to the murder• social networks also include those who might save your life• Bucket Brigades and Telephone Trees• the whole is greater than the sum of its parts• can increase the effectiveness of human beings simply by arranging them differently (particular configurations)• group: can be defined by an attribute (ex: women, Republicans, lawyers) or as a specific collection of individuals to whom we can literally point (ex: "thosepeople, right over there")• social network: collection of people that includes a specific set of connections between those in the group• Types of Networks:• Unconnected group - no ties present• Bucket Brigade - every person (except first and last) is connected to two other people by a mutual tie• Telephone Tree - everyone (except first and last) is connected to three other people, there are no mutual ties• Military Squads - every member knows every other member very well, connections are all two-way• network community: a group of people who are much more connected to one another than they are to the other groups of connected people found in otherparts of the network• shape: a network's structure or topology• Rules of Life in the Network• 2 fundamental aspects of social networks:• connection - deals with who is connected to whom• contagion - deals with what, if anything, flows across the ties (ex: germs, money, violence, fashion, happiness, obesity)• 5 rules:• 1) We shape our network• how many people we're connected to• how densely interconnected our friends and family are• how central we are to the social network• 2) Our networks shape us• 3) Our friends affect us• 4) Our friends' friends' friends affect us• hyperdyadic spread: the tendency of effects to spread from person to person to person, beyond an individual's direct social ties• Milgram's famous sidewalk experiment• decisions of a passerby to copy a behavior were influenced by the size of the crowd exhibiting it• 5) The network has a life of its own• La Ola ("the wave")• not orchestrated by someone with a megaphone, has a life of its own• flocks of birds and schools of fish• emergent properties: new attributes of a whole that arise from the 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" (your friend is one degree from you, your friend's friend is twodegrees, and so on)• Milgram experiment• involved giving a few hundred people who lived in Nebraska a letter addressed to a businessman in Boston, more than a thousand miles away• they were asked to send the letter to someone they knew personally• goal was to get it to someone they thought would be more likely than they to have a personal relationship with the Boston buisnessman• number of hops from person to person that the letter took to reach the target was tracked - on average 6 hops were required• three degrees of influence rule: everything we do or say tends to ripple through our network, having an impact on our friends (one degree), our friends'friends (two degrees), and even our friends' friends' friends (three degrees). • three possible reasons our influence is limited:• intrinsic-decay explanation• by the time information reaches four degrees it may no longer be accurate or reliable • network-instability explanation• we may not have stable ties to people at four degrees of separation given the constant turnover in ties all along the way• evolutionary-purpose explanation• we may not be able to influence people four degrees removed from us because, in our hominid past, there was no one who was four degreesremoved from usChapter 2: When You Smile, the World Smiles with You• Tanzania 1962 - epidemic of laughter at a girl's boarding school• Our Ancestors Had Feelings• emotions consist of several elements• we have a conscious awareness of our emotions - we know when we're happy• they affect our physical state - show how we feel on our faces• they're associated with specific neurophysiological activity• they're associated with visible behaviors - laughing, crying• for our ancestors the spread of emotions probably served an adaptive purpose• Emotional Contagion• emotions spread from person to person because of two features of human interaction: we are biologically hardwired to mimic others outwardly, and inmimicking their outward displays, we come to adopt their inward states • affective afference• ex: if your friend feels happy, she smiles, you smile, and in the act of smiling you also come to feel happy• mirror neuron system• Emotional Stampedes• mass psychogenic illness (MPI): when emotions spread from person to person and affect large numbers of people• An Unbearable Sweetness• outbreaks of epidemic hysteria are not restricted to children and school, they have been documented in adults too• Tracking the Spread of Emotions• experience-sampling method: uses a series of alerts at unexpected times to prompt subjects to document their feelings, thoughts, and actions while theyare experiencing them• The Spread of Happiness• a person is 15% more likely to be happy if directly connected to a happy person (one degree)• 10% more likely at two degrees• 6% more likely at three degrees• each happy friend a person has increases the person's probability of being happy by about 9% and each unhappy person decreases it by 7%• Life on the Hedonic Treadmill• we appear to have a set point for personal happiness that is not easy to change• personal happiness appears to be strongly influenced by our genes• estimated that long term happiness depends 50% on a person's genetic set point. 10% on their circumstances, and 40% on what they choose to think anddo• our friends' happiness has an affect on us, but it only lasts for about a year - we get used to our friends being happy• Alone in the Crowd• loneliness is the feeling of being disconnected• each extra friend reduces by about two days the number of days we feel lonely each year - number of family