The Convergence of Social and The Convergence of Social and Technological NetworksTechnological Networks

By Jon KleinbergBy Jon Kleinberg

Presented by Jonathan WillittsPresented by Jonathan Willitts

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ContentsContents OverviewOverview

Why look into convergence of networksWhy look into convergence of networks

How it is possibleHow it is possible

The small world phenomenonThe small world phenomenon

Social contagion and the spread of ideasSocial contagion and the spread of ideas

Further directionsFurther directions

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OverviewOverview Past decade has witnessed a coming together of the Past decade has witnessed a coming together of the

technological networks that connect computers on the technological networks that connect computers on the Internet, and the social networks that have linked humans Internet, and the social networks that have linked humans for millenniafor millennia

Sites such as Facebook, MySpace, Wikipedia, digg, Sites such as Facebook, MySpace, Wikipedia, digg, del.icio.us, YouTube and flickr have all developed from thisdel.icio.us, YouTube and flickr have all developed from this

Growing Pattern of movements to:Growing Pattern of movements to:• Form connections with others, Form connections with others, • Build virtual communitiesBuild virtual communities• Engage in self expressionEngage in self expression

Data being generated by these online worlds allows us to Data being generated by these online worlds allows us to observe human social interaction in a way never previously observe human social interaction in a way never previously possiblepossible

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Why look into convergence of Why look into convergence of networks?networks?

Images of social networks offer glimpses of Images of social networks offer glimpses of everyday life from an unconventional vantage everyday life from an unconventional vantage point, such as:point, such as:• Flow of information through an organisationFlow of information through an organisation• Disintegration of social groups into rival factionsDisintegration of social groups into rival factions

Science advances when we can take something Science advances when we can take something that was once invisible, and make it visiblethat was once invisible, and make it visible

This is now happening with social networks, and This is now happening with social networks, and social processessocial processes

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How it is possible?How it is possible? Collecting data on social networks has previously been Collecting data on social networks has previously been

hard work, requiring:hard work, requiring:• Extensive contact with group being studiedExtensive contact with group being studied• Limited to much smaller groups (tens or hundreds of Limited to much smaller groups (tens or hundreds of

individuals)individuals)

Online social interactions however leave digital tracesOnline social interactions however leave digital traces

This allows us to collect and use minute by minute data This allows us to collect and use minute by minute data on tens of millions of people to:on tens of millions of people to:• Monitor the way people seek connections and form Monitor the way people seek connections and form

friendships (Facebook)friendships (Facebook)• Coordinate with and engage in creative expressions Coordinate with and engage in creative expressions

(Wikipedia or flickr)(Wikipedia or flickr)• Observe news stories / witness controversy gathering Observe news stories / witness controversy gathering

around communities (bloggers)around communities (bloggers)

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The Small-World Phenomenon / The Small-World Phenomenon / Decentralised Search Decentralised Search

Stanley Milgram experiments in the 1960sStanley Milgram experiments in the 1960s

Milgram asked a few hundred people in Boston and the Milgram asked a few hundred people in Boston and the Midwest to direct a letter towards a stockbroker in Midwest to direct a letter towards a stockbroker in MassachusettsMassachusetts• Gave each the targets name, address and occupationGave each the targets name, address and occupation• Only mail letter to someone they knew on first name basisOnly mail letter to someone they knew on first name basis• Mail with instructions to pass the letter onMail with instructions to pass the letter on

Successful letters reached the target in a median of 6 stepsSuccessful letters reached the target in a median of 6 steps

Play and then film: Six Degrees of Separation Play and then film: Six Degrees of Separation

Game: Six Degrees of Kevin BaconGame: Six Degrees of Kevin Bacon

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Six Degrees of SeparationSix Degrees of Separation

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Other work (MSN Messenger)Other work (MSN Messenger) Social network built from quarter-billion instant Social network built from quarter-billion instant

messaging accounts messaging accounts

Connected individuals who engaged in a conversation Connected individuals who engaged in a conversation over a 1 month periodover a 1 month period

Average length of the shortest path between any two Average length of the shortest path between any two people was 6.6people was 6.6

Very close to Milgram’s figure, obtained completely Very close to Milgram’s figure, obtained completely differentlydifferently• Milgram asked targets to forward letter to people they think Milgram asked targets to forward letter to people they think

might know the targetmight know the target• Studying “random” links made by conversations, participant Studying “random” links made by conversations, participant

unaware. unaware.

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Milgram FindingsMilgram Findings Milgram experiment not only showed that paths existed, Milgram experiment not only showed that paths existed,

but also that people knew how to find thembut also that people knew how to find them

People asked to find the target couldn’t know the course People asked to find the target couldn’t know the course the letter would take, or whether it would get therethe letter would take, or whether it would get there

The fact that so many did shows social networking ability to The fact that so many did shows social networking ability to funnel information towards far away targetsfunnel information towards far away targets

Caveat: the experiments were more successful the more Caveat: the experiments were more successful the more affluent and socially accessible the targetaffluent and socially accessible the target

Many chains failed to completeMany chains failed to complete

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Nexus graphNexus graph

http://nexus.ludios.nethttp://nexus.ludios.net

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Social contagion and the spread of Social contagion and the spread of ideas ideas

Milgram’s experiments aimed to focus Milgram’s experiments aimed to focus messages on particular targetsmessages on particular targets

Information on social networks tends to Information on social networks tends to radiate out in many directions at onceradiate out in many directions at once

Rumours, political messages and online Rumours, political messages and online videos can spread contagiously from videos can spread contagiously from person to person similar to an epidemicperson to person similar to an epidemic

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Diffusion of innovations Diffusion of innovations There is a pattern by which people influence each There is a pattern by which people influence each

other over periods of time (both online / offline) to other over periods of time (both online / offline) to • form new political and social beliefs, form new political and social beliefs, • adopt technologies and adopt technologies and • change personal behaviourchange personal behaviour

Process known as “Diffusion of Innovations”Process known as “Diffusion of Innovations”

Whilst outcomes may be clearly visible, the inner Whilst outcomes may be clearly visible, the inner workings have remained unknownworkings have remained unknown

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Recent studies of contagionRecent studies of contagion The probability of purchasing of books, DVDs and The probability of purchasing of books, DVDs and

music from a large online retailer increased with music from a large online retailer increased with the number of email recommendations a the number of email recommendations a potential customer receivedpotential customer received

Probability of joining a group in an online Probability of joining a group in an online community increases the more friends are community increases the more friends are already a member of the groupalready a member of the group

There is however a “diminishing returns” pattern There is however a “diminishing returns” pattern in which the marginal effect of each successive in which the marginal effect of each successive friend decreases. friend decreases.

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Contagion as a design principle Contagion as a design principle Decentralised search problem at the heart of the small Decentralised search problem at the heart of the small

world phenomenonworld phenomenon

Contagion in networks serves as a design principle for Contagion in networks serves as a design principle for spread of informationspread of information

Early distributed computing work proposed notion of Early distributed computing work proposed notion of “epidemic algorithms” where information updates would be “epidemic algorithms” where information updates would be spread between hosts using a probabilistic contagion rulespread between hosts using a probabilistic contagion rule

Lead to further research based on the fact that these Lead to further research based on the fact that these algorithms can be highly robust and simple to configure at algorithms can be highly robust and simple to configure at each nodeeach node

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Further directionsFurther directions Whilst most of this presentation has been focussed on dynamic Whilst most of this presentation has been focussed on dynamic

behaviour of individuals in social networks, an important behaviour of individuals in social networks, an important complimentary areas is how the structure of the network itself complimentary areas is how the structure of the network itself evolves over timeevolves over time

Recent studies of large datasets have shed light on important Recent studies of large datasets have shed light on important principles of network evolution such as:principles of network evolution such as:• Preferential attachment:Preferential attachment: in which nodes that already have many in which nodes that already have many

links will tend to acquire further ones at a greater ratelinks will tend to acquire further ones at a greater rate

• Triadic closure:Triadic closure: links are more likely to form between two people links are more likely to form between two people when they have a friend in commonwhen they have a friend in common

• Densification effects:Densification effects: in which the number of links per node in which the number of links per node increases as the network growsincreases as the network grows

• Shrinking diameters:Shrinking diameters: in which the number of steps in the shortest in which the number of steps in the shortest path between nodes can actually decrease as the total number of path between nodes can actually decrease as the total number of nodes increasesnodes increases