CSCI 2350: Social & Economic Networks How do behavior, opinion, - - PDF document

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CSCI 2350: Social & Economic Networks

How do behavior, opinion, technology, etc. propagate in a network? “Cascading Behavior in Networks” Reading: Ch 19 EK

Mohammad T . Irfan

Diffusion of innovations

u One’s choice influences others

u Indirect/informational effects – social learning

u Photo/video going viral

u Direct-benefit effects

u Technology adoption– Xbox/PS4, phone, fax, email,

FB

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Examples

u Adoption of hybrid seed corn in Iowa

u Ryan and Gross, 1943

u Adoption of tetracycline by US doctors

u Coleman, Katz, and Menzel, 1966

u Shared ingredients

u Indirect effects u Adoption was high-risk, high-gain u Early adopters had higher socioeconomic status u Social structure was important– visibility of

neighbors’ activity

Success factors of diffusion

u Diffusion of Innovations– Everett Rogers (1995)

u Complexity u Observability u Trialability u Compatibility

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#TheDress

(February 2015)

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Today

u What leads to widespread diffusion? u Modeling diffusion u Connection with the things we know

u Homophily u Clustering u The strength of weak ties

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First model

u “Contagion” – Stephen Morris, 2000

Diffusion vs. strength of weak ties

u Weak ties are conveyors of information u But cannot “force” adoption of behavior

Would Align with own community

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Diffusion vs. clustering

u Assuming a threshold of q, cascade will be

incomplete if and only if there is a cluster of density > 1-q in the “remaining network”

u Cluster density: A fraction s.t. each node in the

cluster has at least that fraction of neighbors in it

density = 2/3 > 1-q for q = 2/5

More general model

u Linear threshold model – Granovetter, 1978