the length of bridge ties: structural and geographic properties of online social interactions

The Length of Bridge Ties: Structural and Geographic Proper9es of

Online Social Interac9ons Y. Volkovich†, S. Scellato‡,

D. Laniado†, C. Mascolo‡, A. Kaltenbrunner†

† Barcelona Media Founda9on ‡ University of Cambridge

13/02/18 KDE Seminar: Yuto Yamaguchi 1

ICWSM 2012

Background

•  Geographically closer pair of individuals are more likely to develop social bonds –  [Merton, 1948], [Fes9nger et al., 1950], …

•  This holds even on online social networking services –  [Liben-‐Nowell et al., 2005], [Backstorm et al., 2010], …


Research Ques9on


What is the rela;onship between the structural proper,es of online social ;es and the spa,al distance

Structure, Tie strength, and Distance

•  Tie strength – Close friends or just acquaintances – Frequency of interac9ons

•  Network structure – Cores, Bridges, Periphery

•  Spa9al distance – Between connected individuals


bridge

core

periphery

strong 9e

Results

•  Individuals at closer distance more likely to establish social connec9ons

•  Social links in the core tend to span shorter distances than outer 9es

•  Interac9on levels are higher inside the core


Dataset


“Spanish Facebook” Founded in 2006 in Spain

Full anonymized snapshot as of Nov. 2010

p  9.8 million users (25% of Spanish popula9on) p  580 million friendship links p  500 million message exchanges in 3 months

Basic Proper9es


N: # of nodes K: # of edges NGC: # of nodes in

giant component <deg>: Average degree <C>: Clustering coefficient

deff: 90% diameter dmax: Maximal distance <dpath>: Average path-‐length <D>: Average spa9al distance

of arbitrary pairs <l>: Average spa9al distance

of connected pairs

Structural posi9on of social 9es (1/2)

•  Local posi9on ( social overlap ) – Connected users with many common friends seem to be inside the core


oi, j = Γi∩Γ j

Γi : set of friends of i

Structural posi9on of social 9es (2/2)

•  Global posi9on ( k-‐index ) – K-‐index measures how middle a node is in the network

– k-‐index of a node is v if it belongs to v-‐core but not to (v+1)-‐core

– K-‐index of an edge eij


The k-‐core is the maximal subgraph where each node connects to at least k nodes inside the subgraph.

kij =min(ki,kj )

Structural posi9on and spa9al length　 (1/2)


Spa,al distance decreases as connected users share more friends

Structural posi9on and spa9al length (2/2)


Social links inside the core are shorter than the ones reaching the periphery

The impact of 9e strength (1/2)


Although likelihood of friendship is correlated to the spa,al distance, ,e strength does not affect the distance

The impact of 9e strength (2/2)


p  Users inside the core more frequently interact

p  Users in the periphery and in the core more frequently interact

Discussion

•  Shorter distance increase the likelihood that users belong to the same dense group.

•  Bridges create not only network shortcuts, but also spa9al shortcuts.

•  Frequent interac9ons occur inside the cores or between the core and periphery.


Conclusion •  Inves9gated how spa9al constraints influence the network structure


Spa9al distance

Spa9al distance

Tie strength

Tie strength

core

core

high

low

high low

the length of bridge ties: structural and geographic properties of online social interactions

Technology