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This is the summary of Connected: The Surprising Power of Our Social Networks written by Nicholas Christakis and James Fowler.

What is the summary of Connected: The Surprising Power of Our Social Networks?

Connected: The Surprising Power of Our Social Networks is a pretty interesting book that isn´t explicitly about social media networks, although it does go through that as well. I would say that the book is more about the foundations of how people behave, interact and attach to each other in the world. If that behavior is online or offline doesn’t really matter.


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I haven’t summarized chapter 5 and 6 since I didn’t find very much interesting there. The summary of Connected: The Surprising Power of Our Social Networks is in total 17 pages and most of the notes come from the beginning of the book. I would say that these notes are great if you´re looking for an introduction to network theory. If you are an advanced user, you´re probably better off reading the book by yourself and pick your own diamonds. You always benefit more from doing your own note since you are creating achors in your head while underlining. This makes i much easier to remember the vital parts of the book.

Visit the book´s website to read more about it:. The site is full of usable material that is a great complement to the book and my notes. Christakis have plublished a guide to all the chapters of the book as well as pdf slides that you can download for free.

Read the summary of Connected


Summary of Connected | Chapter 1: In the thick of it

Social network can be conduits for altruistic acts in which individuals pay back a debt of gratitude by paying it forward.

Beyond our own social horizons, friends of friends of friends can start chain reactions that eventually reach us.

What is a group of people: A group can be defined by an attribute (woman, democrats,
long-distance runners etc.) or as a specific collection of individuals to whom we can literally
point (those people over there, waiting to get into the concert).

What is a network: While a 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. The allow groups to do things that a disconnected collection of individuals cannot. The ties explain why the whole is greater than the sum of its parts. And the specific pattern of the ties is crucial to understanding how networks function.

Network community: A network community can be defined as a group of people who are much more connected to one another than they are to other groups of connected people
found in other parts of the network.

Social networks evolve organically: In a basic sense, 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.

When your family and friends become better connected, it increases your level of connection
to the whole social network. We say it makes you more central because having betterconnected friends literally moves you away from the edges and toward the center of a social network.

Network topology: A networks shape (structure, topology) is a basic property of the network. The buttons in the topology is connected until there are no strings left. Some buttons will have many buttons connected, and some groups of buttons will be connected to each other but separated from each other. These groups are called components.

Rules of life in the network
There are two fundamental aspects of social networks.

  • There is a connection, which has to do with who is connected with to whom. Ties can be causal or intense, personal or anonymous.
  • There is a contagion, which pertains to what, if anything, flows across the ties. It could be buckets of water or whatever.

Rule 1: We shape our network. Homophily is the tendency to associate with people that are
like us. We seek out the people that share our interests, histories, and dreams. We choose the
structure of the network 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

Ex. If you now Alexi, and Alexi know Lucas, and Lucas know you, this relationship is
transitive – the relationship forms a triangle.

Rule 2: Our networks shape us. Having an extra friend may create all kinds of benefits for
your health, even if the other person doesn’t actually do anything for you. 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 also crucial. Social networks transport all kinds of things from one person to another. One fundamental
determinant of flow is the tendency of human beings to influence and copy one another. Each and every tie to different people offers opportunities to influence and to be influenced.

Rule 4: Our friend’s friend’s friends affect us. Hypdyadic spread is the tendency of effects
to spread from person to person to person, beyond an individual’s direct social ties. The usual way we think about contagion is that if one person has something and comes into contact with another person, that contact is enough for the second person to get it. Like getting infected with a germ. But some things – like norms and behaviors – might not spread this way. They might require a more complex process that involves reinforcement by multiple social contacts.

Ex: If we wanted to get people to quit smoking, we would not arrange them in a line and get
the first one to quit and tell him to pass it on. Rather, we would surround a smoker with multiple nonsmokers.

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.

Ex: you cannot understand a traffic jam by interrogating one person fuming at the wheel of
his car, even though his immobile automobile contributes to the problem.

Group of interconnected people can exhibit complicated, shared behavior without explicit
coordination or awareness.

An excitable medium: Flips from one state to another depending on what others around it are doing.

Collective intelligence: behavior that does not reside within individual creatures but, rather
is a property of groups. Each bird contributes a bit, and the flock’s collective intelligence choice is better than individual birds would be.

Emergent properties: Are new attributes of a whole in a social network that arises from the
interaction and interconnection of the parts. A cake, for example, has a taste not found in any
of its ingredients. The taste of the cake transcends the simple sum of its ingredients.

Six degrees of separation: People are all connected to one another by an average of six
degrees of separation.

The three degree influence rule: Social networks obey this rule. Our influence gradually
dissipates and eases to have noticeable effect on people beyond the special frontier that lies
at three degrees of separation. We are generally influenced by friends within 3 degree but general not by those beyond.

Word of Mouth: WOM tend to spread 3 degrees as well.

The intrinsic-decay explanation: When information reaches your friends friends friends
friends, that person may no longer have accurate or reliable information on what you actually did.

The network instability explanation: Influence may decline because of an unavoidable evolution in the network that makes the link beyond 3 degrees unstable. Friends stop being
friends, etc.

The evolutionary-purpose explanation: Biology´s part; in our past, there was no one who
was four degrees removed from us.

Connection and contagion is the structure and the function of social networks. They are the
anatomy and physiology of the human super organism.

In a kind of social chain reaction, we can be deeply affected by events we do to witness that
happen to people we do not know.

A solid network is like a commonly owned forest; we all stand to benefit from it, but we must also work together to ensure it remains healthy and productive.

A person with many friends may become rich and then attract even more friends. This means that social networks can reinforce 2 different kinds of inequality in our society: situational inequality and positional inequality.

The powerful effects of social networks on individual behaviors and outcomes suggest that people do not have complete control over their own choices.


Summary of Connected | Chapter 2: When you smile, the world smiles with you

Emotions have a collective and not just and individual origin. How you feel depends on how
those to whom you are closely and distantly connected feel.

1. We usually have a conscious awareness of our emotions
2. Emotions typically affect our physical state: our faces, our voice, our posture.
3. Emotions are associated with specific neurophysiological activity; if you show a scaryvpicture, the flow of blood to structures deep in your brain instantly changes. Finally, emotions are associated with visible behaviors like laughing, crying etc.

People’s emotions and mood are affected by the emotional states of the people they interact with.

Emotions origin: Early humans had to rely on one another for survival. Their interactions
with the physical environment (weather, predators etc.) were modulated or affected by their
interactions with their social environment.

Emotions for groups: 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
– Communicating information

Emotional contagion: emotions spread from one person to another because of two features of human interaction: we are biologically hardwired to mimic others outwardly, and in mimicking their outward displays, we come to adopt their inward states. Reading the expressions of others was probably a key step on the way toward synchronizing feelings and developing the emotional empathy that underlies the process of emotional contagion.

Affective afference: People imitate the facial expressions of others and as a direct result, they
come to feel as others.

Mirror neuron system: Makes emotions contagious. Our brains practice doing actions we
merely observe in others, as if we were doing them ourselves.

Mass psychogenic illness: When an emotion spread from person to person and affects a
large number of people. A single reaction in one person can sometimes cause many others to
feel the same thing, creating an emotional stampede.

The Proust phenomenon: Memories invoked by smell induce stronger emotions than those
evoked by verbal descriptions of the same odor. Words are powerful, but one familiar whiff can jolt the mind into the past with more emotional intensity than can a signal from any other sense (pp.45).

The experience-sampling method: Uses a series of alerts/signals at unexpected times to prompt subjects to document their feelings, thoughts and actions while experiencing them.

The influence of happy friends: Unhappy people cluster with other unhappy people and vice versa. Unhappy people seem more peripheral; they are much more likely to appear at the end of a chain of social relationships or at the edge of the network. A person is about 15% more likely to be happy if a directly connected person is happy. So having happy friends seem to be a more effective predictor of happiness than earning more money. Eve people that you have never met can have stronger impact on your personal happiness than a wad of hundreds in your pocket.

Once we control for the emotional states in one happy friend, having more friends isn’t enough – having more happy friends is the key to our emotional well-being. The more friends your friends have, the more likely you are to be happy.

Happy people do not tend to become more central so a wide social circle doesn’t have to make you happier. But being happy widens your social circle. Being in the middle of the network leads to happiness.

Hedonic Treadmill: after a lottery win or something else that made you happy people tend
to return to their previous level of happiness. It doesn’t last. We appear to have a set point for personal happiness that is not easy to change.

Long term happiness depends 50% on a person’s genetic set point, 10% on their circumstances (where they live, how rich they are etc.), and 40% on what they choose to think and do.

Loneliness: Loneliness is a complex set of feelings experienced by people whose core needs for intimacy and social connection are not met. Loneliness also spread three degrees.

Battle loneliness: If we are concerned about combating the feeling of loneliness in our society, we should aggressively target the people at the periphery with interventions to repair their social networks. By helping them, we can create a protective barrier against the loneliness that will keep the whole network from unraveling.

Different beliefs, same feelings: people over the world have different ideas, beliefs and opinions, but they have very similar, if not identical, feelings.


Summary of Connected | Chapter 3: Love the one you’re with

The majority of people find spouses and partners by meeting friends of friends and other people to whom they are loosely connected.

Relative versus absolute standing: People often care more about their relative standing in
the world than their absolute standing. People are envious. Many consumer demands arise not from innate needs but from social pressure. People assess how well they are doing not so much by how much money they make or how much stuff they consume, but rather by how much they make and consume compared to other people they know.

You don’t need to be the most beautiful or wealthiest person to get the most desirable
partner; you just need to be more attractive than all the other women in your network. Many
people may be more attractive than we are, but our only real competitors are the people in
our intended social network. One study showed that women ranked married men higher
than unmarried.

The connection of marriage: It also showed that married people lived longer. After the spouse died, the mortality rate for the one that was left rose with 40% during 6 months and then went back to normal. This could be because they both lived unhealthy, something in the
environment where they lived, or because there is a true causal relationship between marriage and health. Being married ads 7 years to a man and 2 years to a woman.

Being near a familiar person can have effects as diverse as lowering heart rate, improving immune function, and reducing depressions. Spouses provide social support to each other and connect each other to the broader social network of friends, neighbors and relatives.

The bigger the age differences between an older husband and a younger wife, the better for
both when it comes to health benefits of marriage.

Multiplexity: The tendency to have several kinds of relationships. Multiplex networks overlap – we can be friends and lover with same persons.


Summary of Connected | Chapter 4: This hurts me as much as it hurts you

People randomly assigned to seats neat strangers who eat a lot wind up doing the same.

Large social networks: Have communities within them, and these communities can be defined not only by their interconnections but also by ideas and behaviors that their embers
come to share.

Imitation: When people are free to do to as they please, they usually imitate. This is one way
obesity might spread from person to person. Imitation can be both cognitive (something we
intentionally think about) and physiological (a natural biological process)

A norm: A shared experience about what is appropriate that spreads from person to person.
People can reinforce particular norms so that directly and indirectly connected people share an idea about something without realizing that they are being influenced by one another.

More connections within groups (concentrated networks) can reinforce a behavior in the groups, but more connections between groups (integrated networks) can open up a group to new behaviors and to behavioral changes.


Summary of Connected | Chapter 5+6

No notes from these chapters.


Summary of Connected | Chapter 7: It’s in our nature

The most important feature of the human environment is the presence of other members of our species. Because we lack any real predators, the only major threat to humans is other human.

We deliberately choose to form social connections with specific individuals, with whom we share greater or lesser intimacy and affection, for brief or lengthy periods of time.

Our desire to form connections depends partly on our genes. Evolution likely plays a role in the way we connect to one another because the very act of connection is itself subject to natural selection.

People often ignore their selfish tendencies when interacting with people to whom they are connected. Across a wide variety of laboratory experiments that study dilemma in altruism and cooperation, people choose to help other people about half the time, even people they will never interact with again.

Direct reciprocity: If you have several opportunities to cooperate with the same person, one
way to get that person to help you is to promise future cooperation. Robert Axerod showed that a cooperative strategy called “tit for tat” often is more effective than always cooperating or always being selfish. In tit for tat, you cooperate the first time you meet someone, and thereafter simply copy what that person did the last time you interacted with him.

Punishers: Cooperation can emerge because we can do more together than we can apart. But
because of the free-rider problem, cooperation is not guaranteed to succeed. To deal with free riders, another type of person is needed: punishers. Cooperators connect to others in order to create more: free riders connect in order to leach of those who create; and punishers connect in order to drive away free riders.

Because we are connected to others, and because we have evolved to care about others, we take the wellbeing of others into account when we make choices about what to do. We want what others to whom we are connected want.

Cooperation, altruism, punishment and free riding are written into our DNA. There is evidence that diversity in these social preferences may be at least partly a result of our genetic evolution.

Lonely vs. being alone: Feeling lonely is not the same thing as being alone. Feelings of loneliness can arise from the discrepancy between our desire for social connection and our actual social connections. Half of the variation in whether a person feels lonely or not depends on his genes.

The number of possible relationships grows exponentially with group size.

Dunbar’s number: Dunbar examined the relationships between brain size and group size in
a variety of primates and by extrapolation posited that the expected size of social groups in human, based on our big brains, should be about 150. Dunbar argued that language emerged
among humans, in part, to replace grooming. Basically, language is a less yucky and more efficient way to get to know our peers since we can talk to several friends at once but only groom them one at a time. The social perspective on language suggests that it evolved as a means of maintaining group cohesion.

Groups: Human conversational groups should be about four people – 1 speaker and 2, 8


Summary of Connected | Chapter 8: Hyper connected

Advantages of good looks: Our physical appearance affects the way others treat us. For example, people attract more friends, are paid a higher wage for the same work, and are often seen as more deserving of treatment by health care workers when they are tall or good looking.

Social network sites: The distinctive features of social network sites are that it makes our web of connections visible to the user and to others. Moreover, unlike other sorts of online groups or communities like wikis and listservs, social network sites are organized around
people, not topics.

At their core, social network sites primarily reflect offline interactions. Although they allow us to maintain contact with people whom we would otherwise be tied only weakly, they are not organized around the introduction of strangers.

The internet makes possible new social forms that are radical modifications of existing types of social network interactions in four ways:

Enormity. A vast increase in the scale of our networks and the numbers of people
who might be reached to join them.

Communality. A broadening of the scale by which we can share information and
contribute to collective efforts.

Specificity. An impressive increase in the particularity of the ties we can form.

Virtuality. The ability to assume virtual identities.

Online networks do not appear to expand the number of people with whom we feel truly close, nor do they necessarily enhance our relationships within our core groups.


Summary of Connected | Chapter 9: The whole is great

Collective intelligence: Social networks can manifest a kind of intelligence that augments or
complements individual intelligence, the way an ant colony is intelligent even if individual ants are not. Networks can have this effect regardless of the intelligence of the individual members.

Trust in networks: In many cases, it is not just that the people in your network are more trusting, or even that their trusting behavior engenders trust in you; rather, the network facilitates this trust and changes the way individuals behave.

Social networks are often self-annealing. One person might step out of a bucket brigade, but then the two people he was connected to will move closer to each other, forming a new connection to fill the gap. As a result, water will continue to flow.