Experiments!
Direct Influence
Three Degrees of Influence
Alter Influence Persists
Alter’s Alter Influence Persists
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
The Network Acts Like a Matching Grant Each a Person Gives in First Round.... Causes Others to Give
105 Close Friends in a Dorm
Friends and Ethnic Clubs
Friends, Clubs, Roommates,
Friends, Clubs, Roommates, plus Facebook!
Smilers NonSmilers
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
Social Message N = 60,055,176
Message about user voting appears in news feed
Message Only N = 611,044
No Message N = 613,096
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!
Vote Validation 6 Million Users 13 States (1/3 of population) “Yahtzee” procedure to protect anonymity 33% match rate
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
Informational Message Social Message a
Compare political behavior of friends of the treatment group to friends of the control group Measuring Social Contagion
Are close friends more influential? Friendship on Facebook “Find a Friend” project Contacts a measure of tie strength
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.
Measuring “Close” Friends
Distribution of Friends 8.3 Billion Non-close Friends 767 Million Close Friends 16 Billion Close Friends of Close Friends
Does your friend’s mobilization affect your voting behavior? Social Contagion
Testing for Significance 3/5 7/15 8/25 2/5 6/15 10/25 RANDOM NETWORK OBSERVED NETWORK
0 =
0 = N.S.
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
Total Effects