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Social networks and information sharing. Lada Adamic. Outline. Individual contributors: Is narrow focus of benefit? Should they draw on knowledge in other disciplines? What motivates individuals to volunteer information? How does money and competition affect that motivation? The network:
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Social networks and information sharing Lada Adamic
Outline • Individual contributors: • Is narrow focus of benefit? • Should they draw on knowledge in other disciplines? • What motivates individuals to volunteer information? • How does money and competition affect that motivation? • The network: • What role do social networks play in information diffusion? • Are online networks truthful and representative of trust? • The information: • How does information change as it diffuses?
Knows Knowledge iN Focus and quality in knowledge contribution • study 4 knowledge contribution contexts • scholarly publications (1900-2008) • patents (1976-2006) • Q&A forums (Yahoo! Answers, Baidu, Naver) • Wikipedia • main finding: • focus trumps quantity in explaining quality of contribution Adamic, Wei, Yang, Nam, Clarkson, First Monday, 2010
Focus and knowledge contribution PATENTS PAPERS WIKIPEDIA CQA
Impact of information diffusion across communities • study scholarly citation networks (JSTOR, patents) • does drawing from other areas (i.e. citing outside one’s field) translate to having higher impact? • social sciences and humanities: no • natural sciences and patents: yes Shi, Adamic, Tseng, PLoS One, 2009
Knowledge iN Motivation and quality in information sharing • Analyze 2.6 million questions, 4.6 million answers + 26 interviews of top answerers • Users who contribute more often and less intermittently contribute higher quality information • Users prefer to answer unanswered questions and to correct incorrect answers • What motivates individuals to contribute in online Q&A forums? • altruism • learning • competition (point system) Nam, Ackerman, & Adamic, CHI’2009
Monetary incentives and contribution • Crowdsourcing: 120 translation tasks • all pay auction mechanism: participants contribute solutions, only 1 is selected to receive payment • price treatment: high, low • shill treatment: enter in our own solution as a user with or without prior success • results • monetary incentives incentivize spam(85% are machine translations) • higher pay yields better contributions • shills discourage other quality contributions Liu, Yang, Adamic, Chen
Social dynamics of information in virtual spaces (e.g. Second Life) • Items diffusing through social network spread more rapidly but have limited range • Early adopters are distinct from connectors • Sellers who chat with customers enjoy more repeat business, but social interaction doesn’t scale Bakshy, Karrer Adamic EC’09, Bakshy,Simmons,Huffaker,Teng, Adamic, Best Paper @ ICWSM’10
Can online social networks be used as a proxy of trust and reputation? • Goal: • Understand basis of trust and friendship • Understand causes of bias in online trust ratings • Data: • 600K CouchSurfing users, 3 million ratings • Amazon & Epinions ratings • Findings: • When ratings are public, and when there is potential for reciprocity, ratings are overlypositive Surfing a Web of Trust: Reputation and Reciprocity on CouchSurfing.com, SIN’09 I rate you. You rate me. Should we do so publicly? WOSN 2010
Reciprocity in CouchSurfing • Public friendship ratings are more highly correlated (rho = 0.73) than private trust ratings (rho = 0.39)
Can trust be equated with friendship? • Close friendship -> high trust • High trust -> variable friendship • Trust and friendship strengthen over time, but rate varies by individual
Predicting trust (person to person “vouches”) • Trust is localized/contextual • Trust is not the same as friendship • Global metrics do not perform as well as local ones
tracing information across the web How do memes change as they diffuse length sentiment content How does their diffusion/evolution depend on the underlying network structure? length of phrase duration in days Simple Polya’s urn model of copying ABCDEFGH CDEF BCDE DEF CDEF Simmons, Adar, Adamic
For more information • http://netsi.org Networks research group at the School of Information, University of Michigan • ladamic@umich.edu • Students: • Xiaolin Shi (PhD 2009, now postdoc at Stanford) • Chun-Yuen Teng (current PhD student) • Matthew Simmons (current PhD student) • Xiao Wei (MSI 2010)