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Do Diffusion Protocols Govern Cascade Growth?

Do Diffusion Protocols Govern Cascade Growth?

Large cascades can develop in online social networks as people share information with one another. Though simple reshare cascades have been studied extensively, the full range of cascading behaviors on social media is much more diverse. Here we study how diffusion protocols, or the social exchanges that enable information transmission, affect cascade growth, analogous to the way communication protocols define how information is transmitted from one point to another. Studying 98 of the largest information cascades on Facebook, we find a wide range of diffusion protocols – from cascading reshares of images, which use a simple protocol of tapping a single button for propagation, to the ALS Ice Bucket Challenge, whose diffusion protocol involved individuals creating and posting a video, and then nominating specific others to do the same. We find recurring classes of diffusion protocols, and identify two key counterbalancing factors in the construction of these protocols, with implications for a cascade’s growth: the effort required to participate in the cascade, and the social cost of staying on the sidelines. Protocols requiring greater individual effort slow down a cascade’s propagation, while those imposing a greater social cost of not participating increase the cascade’s adoption likelihood. The predictability of transmission also varies with protocol. But regardless of mechanism, the cascades in our analysis all have a similar reproduction number (≈1.8), meaning that lower rates of exposure can be offset with higher per-exposure rates of adoption. Last, we show how a cascade’s structure can not only differentiate these protocols, but also be modeled through branching processes. Together, these findings provide a framework for understanding how a wide variety of information cascades can achieve substantial adoption across a network.

Presented at ICWSM 2018.

Justin Cheng

June 26, 2018
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  1. Justin Cheng, Jon Kleinberg, Jure Leskovec, David Liben-Nowell,
    Bogdan State, Karthik Subbian, and Lada Adamic

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  2. i.e., how do memes go viral?
    how
    (not why)

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  3. Prior work
    Cha, et al. (2009, 2010); Romero, et al. (2011); Goel, et al. (2012); Weng, et al. (2013); Cheng, at al. (2014, 2016)
    cascade growth prediction
    cascade recurrence
    contagion/diffusion models
    network structure
    network evolution
    social influence

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  4. A focus on reshare cascades
    Prior work
    Hubs crucial to growth
    Simple replication
    Goldenberg, et al. (2009); Cheng, at al. (2014)
    cascade growth prediction
    cascade recurrence
    contagion/diffusion models
    network structure
    network evolution
    social influence

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  5. Types of cascades
    (This figure for illustrative purposes only.)
    Reshare Cascades
    Other Cascades

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  6. What other types of cascades exist?

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  7. Reshare Post

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  8. Reshare Post Ice Bucket Challenge Post

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  9. 17M videos
    200K participants
    2M supporters

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  10. Do different social mechanisms
    influence cascade growth?
    Research Question
    diffusion protocols
    Explain variations in cascade growth

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  11. What is a diffusion protocol?

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  12. Inspiration: Communications Protocols
    Client Server
    1. SYN
    2. SYN-ACK
    3. ACK

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  13. Inspiration: Communications Protocols
    Client Server
    1. SYN
    2. SYN-ACK
    3. ACK

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  14. Inspiration: Communications Protocols
    Client Server
    1. SYN
    2. SYN-ACK
    3. ACK

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  15. Inspiration: Communications Protocols
    Client Server
    1. SYN
    2. SYN-ACK
    3. ACK

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  16. Transient Copy Protocol

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  17. Transient Copy Protocol

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  18. Transient Copy Protocol

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  19. Nomination Protocol
    Transient Copy Protocol

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  20. Nomination Protocol
    Transient Copy Protocol

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  21. Nomination Protocol
    Transient Copy Protocol

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  22. Transient Copy
    Diffusion Protocols
    Nomination

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  23. Transient Copy Persistent Copy Nomination Volunteer
    Diffusion Protocols

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  24. Transient Copy Persistent Copy Nomination Volunteer
    Also see: State and Adamic (2015)
    Diffusion Protocols

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  25. Transient Copy Persistent Copy Nomination Volunteer
    Diffusion Protocols

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  26. Transient Copy Persistent Copy Nomination Volunteer
    Diffusion Protocols

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  27. Transient Copy Persistent Copy Nomination Volunteer
    Each protocol can generate large cascades!
    ~1M adoptions
    per cascade
    ~800K adoptions
    per cascade
    ~6M adoptions
    per cascade
    ~1M adoptions
    per cascade

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  28. Diffusion protocols
    govern cascade growth
    Our Hypothesis
    Individual effort Social cost

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  29. Participation requires individual effort
    Marwell, Oliver, and Prahl (1988)

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  30. Participation can have social costs
    Milgram (1969); Granovetter (1978); Banerjee (1992)

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  31. Participation can have social costs
    Cialdini (1993); Goffman (1967)

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  32. How does individual effort and
    social cost explain differences?

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  33. Cascades on Facebook
    98 large cascades 200M users
    4 protocols
    (All data was de-identified and analyzed in aggregate.)

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  34. How do cascades of different
    diffusion protocols vary on…
    1 Propagation Speed
    2 Reliance on Hub Nodes
    3 Tie Strength
    4 Simple or Complex Diffusion

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  35. How do cascades of different
    diffusion protocols vary on…
    1 Propagation Speed
    2 Reliance on Hub Nodes
    3 Tie Strength
    4 Simple or Complex Diffusion

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  36. How quickly do these
    cascades propagate?

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  37. Persistent Copy Nomination
    % Users
    How quickly do cascades propagate?
    26
    21 211 216
    0%
    12%
    24%
    0%
    5%
    10%
    15%
    Transient Copy Volunteer
    Adoption Delay (s)
    221 26
    21 211 216 221
    0%
    8%
    16%
    0%
    8%
    16%

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  38. Persistent Copy Nomination
    % Users
    Copy cascades spread quickly…
    26
    21 211 216
    0%
    12%
    24%
    0%
    5%
    10%
    15%
    Transient Copy Volunteer
    Adoption Delay (s)
    221 26
    21 211 216 221
    0%
    8%
    16%
    0%
    8%
    16%

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  39. Persistent Copy Nomination
    % Users
    …while non-copy cascades spread slowly
    26
    21 211 216
    0%
    12%
    24%
    0%
    5%
    10%
    15%
    Transient Copy Volunteer
    Adoption Delay (s)
    221 26
    21 211 216 221
    0%
    8%
    16%
    0%
    8%
    16%
    ~ 1 day

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  40. Transient Copy Nomination
    Increasing effort reduces propagation speed
    Less effort?
    More effort?

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  41. Transient Copy Volunteer
    Increasing effort reduces propagation speed
    2
    1
    3
    4
    1

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  42. How do cascades of different
    diffusion protocols vary on…
    1 Propagation Speed
    2 Reliance on Hub Nodes
    3 Tie Strength
    4 Simple or Complex Diffusion

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  43. Are hubs always crucial in the
    development of large cascades?
    Goldenberg, et al. (2009); Hinz, et al. (2011); Cheng, et al. (2014)

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  44. Persistent Copy Nomination
    How significant are hub nodes?
    Transient Copy Volunteer
    % Adoptions Originating from the Top 1% of Users
    10
    0 20 30 40 10
    0 20 30 40

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  45. Persistent Copy Nomination
    Low-effort cascades benefit more from hubs
    Transient Copy Volunteer
    % Adoptions Originating from the Top 1% of Users
    10
    0 20 30 40 10
    0 20 30 40
    13.7 7.6
    5.8
    37.3

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  46. Hubs Non-Hubs
    Katona, et al. 2011
    Hubs are less influential per individual

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  47. How do cascades of different
    diffusion protocols vary on…
    1 Propagation Speed
    2 Reliance on Hub Nodes
    3 Tie Strength
    4 Simple or Complex Diffusion

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  48. Does tie strength vary
    across cascades?

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  49. Persistent Copy Nomination
    How does tie strength vary?
    Transient Copy Volunteer
    # Mutual Friends
    20
    0 40 60 80 20
    0 40 60 80

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  50. Persistent Copy Nomination
    Transient copy cascades use weaker ties…
    Transient Copy Volunteer
    # Mutual Friends
    20
    0 40 60 80 20
    0 40 60 80
    28.8

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  51. Persistent Copy Nomination
    …while other cascades use stronger ties
    Transient Copy Volunteer
    # Mutual Friends
    20
    0 40 60 80 20
    0 40 60 80
    28.8 44.6
    58.1
    70.7

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  52. Transient Copy Nomination
    Social costs invoke strong ties
    Lower
    social cost
    Greater
    social cost

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  53. Transient Copy Persistent Copy
    Social costs invoke strong ties
    Demonstrates
    group
    belonging

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  54. How do cascades of different
    diffusion protocols vary on…
    1 Propagation Speed
    2 Reliance on Hub Nodes
    3 Tie Strength
    4 Simple or Complex Diffusion

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  55. Is the diffusion process
    simple or complex?
    Centola and Macy (2007)

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  56. Persistent Copy Nomination
    P(Adopt)
    Is diffusion simple or complex?
    3
    1 5 7
    Transient Copy Volunteer
    # Prior Exposures
    9 3
    1 5 7 9
    0
    0.003
    0.006
    0.009
    0
    0.002
    0.004
    0.006
    0
    0.06
    0.12
    0.18
    0
    0.003
    0.006
    0.009

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  57. Persistent Copy Nomination
    P(Adopt)
    Social costs can increase adoption rates
    3
    1 5 7
    Transient Copy Volunteer
    # Prior Exposures
    9 3
    1 5 7 9
    0
    0.002
    0.004
    0.006
    0
    0.003
    0.006
    0.009
    0
    0.003
    0.006
    0.009
    0
    0.06
    0.12
    0.18

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  58. Persistent Copy Nomination
    P(Adopt)
    Complexity depends on cascade type
    3
    1 5 7
    Transient Copy Volunteer
    # Prior Exposures
    9 3
    1 5 7 9
    0
    0.002
    0.004
    0.006
    Complex
    0
    0.003
    0.006
    0.009
    Simple
    0
    0.003
    0.006
    0.009
    0
    0.06
    0.12
    0.18

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  59. Transient Copy Persistent Copy
    Social proof leads to complex diffusion

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  60. Individual effort and social cost
    influence cascade growth

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  61. Transient Copy Persistent Copy Nomination Volunteer

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  62. High
    Indiv. Effort
    Low
    Indiv. Effort
    Low Social Cost
    High Social Cost
    Persistent Copy Nomination
    Transient Copy Volunteer

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  63. High
    Indiv. Effort
    Low
    Indiv. Effort
    Low Social Cost
    High Social Cost
    Hub-Centric
    Strong Ties
    Complex Diffusion
    Fast
    Persistent Copy
    Not Hub-Centric
    Strong Ties
    Simple Diffusion
    Slow
    Nomination
    Hub-Centric
    Weak Ties
    Simple Diffusion
    Fast
    Transient Copy
    Not Hub-Centric
    Strong Ties
    Complex Diffusion
    Slow
    Volunteer

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  64. How do cascades of different
    diffusion protocols vary on…
    1 Propagation Speed
    2 Reliance on Hub Nodes
    3 Tie Strength
    4 Simple or Complex Diffusion

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  65. How do cascades of different
    diffusion protocols vary on…
    1 Propagation Speed
    2 Reliance on Hub Nodes
    3 Tie Strength
    4 Simple or Complex Diffusion
    5 Adoption Rate

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  66. How do adoption rates
    vary across cascades?

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  67. How do adoption rates vary?
    (Considering only non-leaf nodes)
    % Users Adopted
    0%
    15%
    30%
    45%
    60%
    # Users Exposed
    0 75 150 225 300

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  68. How do adoption rates vary?
    (Considering only non-leaf nodes)
    % Users Adopted
    0%
    15%
    30%
    45%
    60%
    # Users Exposed
    0 75 150 225 300
    Ice Bucket Challenge cascade

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  69. How do adoption rates vary?
    (Considering only non-leaf nodes)
    % Users Adopted
    0%
    15%
    30%
    45%
    60%
    # Users Exposed
    0 75 150 225 300
    Transient copy cascade
    Ice Bucket Challenge cascade

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  70. Adoption rates drop as exposures increase
    (Considering only non-leaf nodes)
    % Users Adopted
    0%
    15%
    30%
    45%
    60%
    # Users Exposed
    0 75 150 225 300
    Transient Copy
    Persistent Copy
    Nomination
    Volunteer

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  71. The reproduction number is constant!
    (Considering only non-leaf nodes)
    % Users Adopted
    0%
    15%
    30%
    45%
    60%
    # Users Exposed
    0 75 150 225 300
    y =
    1.81
    x

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  72. Parallels with r/K selection theory
    Pianka (1970)
    K-selected Species
    r-selected Species
    Stayin’ alive!

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  73. Parallels with r/K selection theory
    “K-selected” Protocol
    “r-selected” Protocol

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  74. Parallels with r/K selection theory
    “K-selected” Protocol
    “r-selected” Protocol

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  75. Large cascades can result from
    diverse diffusion protocols

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