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Big Data, Social Networks, and Human Behavior Jukka-Pekka Onnela Harvard University Big Data for Development United Nations Headquarters, New York City July 10, 2012Tuesday, July 10, 2012 1

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Overview • Progress in science has always been driven by data • Explosion in the amount and type of data • “Big data” refers to large and complex data sets • Often multidimensional, longitudinal, digitally generated • The big data phenomenon has its origin in Moore’s law: • The number of transistors on integrated circuits doubles every 18 months • Sensors are cheaper, smaller, everywhere • Enhanced computational capacity http://en.wikipedia.org/wiki/Moore%27s_lawTuesday, July 10, 2012 2

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http://www.boston.com/bigpicture/2008/08/the_large_hadron_collider.htmlTuesday, July 10, 2012 3

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Large Hadron Collider (LCH) • Large Hadron Collider (LHC) at CERN is the biggest machine ever built • Largest underground ring has a circumference of 27 kilometers (17 miles) • 1232 dipole magnets, each 15 meters long weighing 30 tons • Vacuum is 10 trillionth of an atmosphere • Experiments generate 100MB of data (particle trajectories) each second • Higgs boson http://www.runfam.com/2011/10/why-the-hare-may-never-beat-the-tortoise-zenos-paradox-the-paradox-of-motion/Tuesday, July 10, 2012 4

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Networks and mobile sensing • Mobile phones have been used in the past few years to study the structure of human social and communication networks • Networks consist of nodes (actors) and ties (interactions) • The field of research that studies networks, their structure and function, is called network science (in physics and mathematics) or social network analysis (in sociology and statistics)Tuesday, July 10, 2012 6

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Networks and mobile sensing • Network theory, when applied to social networks, has a simple premise • People are connected, therefore our health is connected • People are connected, therefore our economic wellbeing is connected • Mobile phones have enormous potential for the study of human social networks and human behavior “in vivo,” in a natural context outside laboratories • Social behavior has remained essentially unchanged for millennia, but now, for the first time, we have the opportunity to study it at large scaleTuesday, July 10, 2012 7

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Networks and mobile sensing • Besides communication, smartphones have sensors and computing capabilities • These possibilities have led to a new research field called mobile phone sensing • Mobile sensing has evolved in the past few years for several reasons (1) Availability of cheap embedded sensors • Gyroscope, compass, accelerometer, proximity sensor, ambient light sensor, two cameras, microphone, GPS, WiFi, Bluetooth (2) Smartphones are programmable (3) Software can be easily distributed (4) Significant computational power (phone & cloud) • Each phone can generate 1kB of data / second (conservative)Tuesday, July 10, 2012 8

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http://desktopwallpaperdownload.files.wordpress.com/2012/02/network-space-lights-planets-high-wallpapers-full-hd.jpgTuesday, July 10, 2012 9

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Networks and mobile sensing • Expect 6 billion phone subscriptions by the end of 2012 • This results in 6 million MB / second, or 6 TB / second, of data • This is 60,000 more data than CERN generates (conservative) • Twofold opportunity: • Use mobile phone sensing to learn about the individuals (nodes) • Use mobile phone communication patterns and network theory to learn about the structural connections between individuals (ties)Tuesday, July 10, 2012 10

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Phone calls and texts in a European network • 20% market share • 18 weeks (126 days) • Private subscriptions • N = 7M; L = 23M Animation by Mikko Kivelä, Aalto UniversityTuesday, July 10, 2012 11

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Tie strengths in social networks The weak ties hypothesis Mark Granovetter, The strength of weak ties, American Journal of Sociology 78, 1360, 1973Tuesday, July 10, 2012 12

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Tie strengths in social networks Revisiting the hypothesis with aggregated cell phone data • Tie strength • Fraction of friends in common 7 min 15 min (3 calls) 5 min 3 min Onnela, Saramäki, Hyvönen, Szabó, Lazer, Kaski, Kertész, Barabási Structure and tie strengths in mobile communication networks, PNAS 104, 7332, 2007Tuesday, July 10, 2012 13

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Tie strengths in social networks Onnela, Saramäki, Hyvönen, Szabó, Lazer, Kaski, Kertész, Barabási Structure and tie strengths in mobile communication networks, PNAS 104, 7332, 2007Tuesday, July 10, 2012 14

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Pulse of the nation: Mood from Twitter Understanding the Demographics of Twitter Users; A Mislove, S Lehmann, YY Ahn, JP Onnela, JN Rosenquist; Proceedings of the Fifth International AAAI Conference on Weblogs and Social Media, Barcelona, Spain, 2011Tuesday, July 10, 2012 20

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Thank you jponnela.comTuesday, July 10, 2012 22