1. Experiments!

6. Direct Influence

7. Three Degrees of Influence

8. Alter Influence Persists

9. Alter’s Alter Influence Persists

10. Period 1 Eleni Lucas Lysander Erika Harla Erika James Jay Brecken Period 2Period 3Period 4 Lucas Erika Jay Effects Persist Over Time Behavior Spreads 3 Degrees of Separation Degrees of Separation from Eleni 1 2 3

11. The Network Acts Like a Matching Grant Each a Person Gives in First Round.... Causes Others to Give

13. 105 Close Friends in a Dorm

14. Friends and Ethnic Clubs

15. Friends, Clubs, Roommates,

16. Friends, Clubs, Roommates, plus Facebook!

17. Smilers NonSmilers

19. Voting Voting highly correlated in friends & family (Berelson, Lazarsfeld, McPhee 1954) Mobilization is “contagious” (Nickerson 2008) Can voting spread online? We conducted a massive randomized controlled trial on Facebook in 2010

20. Social Message N = 60,055,176

21. Message about user voting appears in news feed

22. Message Only N = 611,044

23. No Message N = 613,096

24. Hash voter data, use hash to assign a group Measure group turnout Hash Facebook data, use hash to assign a group Assign turnout based on match groups Repeat until desired level of accuracy is obtained Do stats on group turnout vs. group treatment Yahtzee!

25. Vote Validation 6 Million Users 13 States (1/3 of population) “Yahtzee” procedure to protect anonymity 33% match rate

26. Social MessageMessageNo Message Age34.71(0.02)34.70(0.02)34.72(0.02) Female41.23%(0.06%)41.28%(0.06%)41.29%(0.06%) Partisan0.20%(0.01%)0.20%(0.01%)0.20%(0.01%) Ideologue0.82%(0.01%)0.82%(0.01%)0.81%(0.01%) Liberal0.38%(0.01%)0.39%(0.01%)0.39%(0.01%) Conservative0.47%(0.01%)0.48%(0.01%)0.48%(0.01%) Democrat0.12%(0.00%)0.12%(0.00%)0.12%(0.00%) Randomization Check

27. Informational Message Social Message a

28. Compare political behavior of friends of the treatment group to friends of the control group Measuring Social Contagion

29. Are close friends more influential? Friendship on Facebook “Find a Friend” project Contacts a measure of tie strength

30. Measuring “Close” Friends Think of the people you have spent time with in your life, your friends with whom you have a close relationship. Your friends might also include family members, neighbors, coworkers, classmates, advisors, and so on. Please list your best friend first, then your next best friend, and so on. You may name up to ten people.

31. Measuring “Close” Friends

33. Distribution of Friends 8.3 Billion Non-close Friends 767 Million Close Friends 16 Billion Close Friends of Close Friends

34. Does your friend’s mobilization affect your voting behavior? Social Contagion

35. Testing for Significance 3/5 7/15 8/25 2/5 6/15 10/25 RANDOM NETWORK OBSERVED NETWORK

36. 0 = +0.011

37. 0 = N.S.

39. Close FriendsFriends Friends of Friends Expressed Vote 0.9%560k1.4%890k1.7% 1025 k Validated Vote 1.8%280k--- Polling Place Search 0.1%70k--- Friend Effects

40. Total Effects