Connected Chapter 1

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Chapter 1
In the Thick of It
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The simplest network is a dyad or pair

• Dyads agglomerate to form
• large interconnected webs

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embedded the degree to which a person is
connected within a network
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The Bucket Brigade

• Linear

Mutual ties (flow in both directions)
Photo from FEMA
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The Telephone Tree

• Information is directional (inbound and outbound
  ties)

Reduces number of steps
Creates cascade effect
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The Military Squad
Tightly interconnected groups
Two-way tie between all members of squad

• Squad is more intra-connected
• than inter-connected with other squads

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Terms
A Social Network consists of all the connections
and ties within a group or collection of groups
A group is a collection of individuals defined by
a common attribute (it need not contain
information about connections)
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Terms
The Shape of a network its structure or
topology
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Terms

• Contagion what flows across ties
• (germs, money, violence, fashions,
• organs, happiness, obesity, etc.)
• Connection
• who is connected to whom
• (ties to family, friends, co-workers, etc.)
• Homophily
• the tendency to associate with people who
  resemble ourselves
• (love of being alike)

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We shape our network

• We determine structure of our network
• how many people we are connected to

The average American has 4 close social contacts
known as their core discussion network The
same number of people can be arranged and
connected in different ways, and have different
topologies
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We shape our network
2. We influence the density of interconnections
between friends and family
we introduce friends from separate groups to one
another
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We shape our network
3. We control how central we are within the
social network
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Transitivity
Transitivity a relationship is transitive when
all those involved know each other (form a
triangle)
Those with high transitivity (e.g. person A) are
deeply embedded within a single group
Those with low transitivity (e.g., person B) act
as a bridge between different groups, connected
with people who do not know one another
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Influence
Contagion what flows across ties (germs, money,
violence, fashions, organs, happiness, obesity)
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What Are You Looking At?
Stanley Milgrams sidewalk experiment exploring
the importance of reinforcement from multiple
people

• Planted actors or stimulus crowds of different
  size to stare up at a window across the street
• Passersby are filmed to record reactions--stop
  and stare/glance up
• Crowd of 1 4 of pedestrians stopped
• Crowd of 15 40 stopped, 86 glanced up
• Crowd of 5 induced almost the same effect as
  15!

Passersby were influenced in deciding to copy a
behavior by the size of the crowd exhibiting it
Photo by David Sim
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Six Degrees of Separation
Stanley Milgram experiment showing that people
are all connected by an average of six steps

• A citizen in Nebraska was instructed to mail a
  letter to someone who they thought would know a
  particular business man in Boston
• The goal was to measure the number of steps for
  the letter to reach the business man
• On average, required six steps
• Replicated on global scale with same results!

Its a small world after all
Photo by Dan Coulter
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Three Degrees of Influence
The influence of actions ripples through networks
3 degrees (to and from your friends friends
friends)
You are affected by people you dont even know!

• Influence dissipates after 3 degrees because
• Intrinsic decay corruption of information
• (like the game telephone)
• -Network Instability social ties become unstable
  at 4 degrees of separation
• -Evolutionary Purpose we evolved in small groups
  where everyone was connected by 3 degrees or less

Photo by Taro Taylor
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Three Degrees of Influence
If we are connected to everyone by 6 degrees and
influence those up to 3 degrees, then we can
reach halfway to the whole world!
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Photo by Wonderworks, Flikr