tools for network interventions - inspq · tools for network interventions november 28, 2012...
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Tools for Network Interventions
November 28, 2012
M t é l Q bMontréal, Quebec
Thomas W. Valente, PhDProfessor, Institute for Prevention Research
d k h l f dPreventive Medicine, Keck School of MedicineUniversity of Southern California
Simulation w/ 3 Initial Adopter Conditions
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Opinion Leaders
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Steps to Opinion Leader InterventionsSteps to Opinion Leader Interventions
1) Collect/obtain network data)
2) Identify opinion leaders
3) Recruit them as champions
4) Convert them (if need be)
5) A i t th i th i b h i5) Assist them in their behavior change promotions
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There are Several Issues
1. Other Centrality Measures
2. Stage of Diffusion
3. Bridges
4. Marginals
5. Low Threshold
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Network PositionsNetwork Positions
BridgesPeripherals
Group Members
Central MembersIsolate
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1. At least 10 Other Measures of Centrality & Multiple Algorithms
• Degree
• Closeness
• Betweenness
• Eigenvector
• Power
• Information
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2. Different Leaders for Different Stages
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Degree
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Closeness
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33. Identify Bridging Nodes. Identify Bridging Nodes
• Leaders are important within groups
• Bridges may be critical to diffusion between groups
• Bridges may be less “burdened” than leaders.
• Bridges may be more amenable to change.
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Two Kinds of BridgesTwo Kinds of Bridges
• Mediators/Brokers (Gould & Fernandez):
C di t–Coordinator
–Consultant
–Gatekeeper
–Representative
– LiaisonLiaison
• Sociometric Bridges: Links, on average, are most critical in the network.
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44. Identify Isolates or Peripherals. Identify Isolates or Peripherals
• Individuals on the periphery of the network or isolates receive information late or not at all.
• In some settings, isolates may be at increased mental health risk.
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55. Identify Low Threshold adopters. Identify Low Threshold adopters
• Individuals with low thresholds innovate early.
• They require fewer initial adoptersl
• They are experienced at persuading others.
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Network Thresholds
= Non= Non--FP UserFP User = FP User= FP User
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PN Exposure=33%PN Exposure=33% PN Threshold=33%PN Threshold=33% PN Threshold=66%PN Threshold=66%
Low Threshold AdopterLow Threshold Adopter High Threshold AdopterHigh Threshold Adopter
Graph of Time of Adoption by Network Threshold for One Korean Family Planning Community
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1824293037 4044466616265
Threshold
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414953 64
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Sociometric v. Self Reported OL
• Correlated at approximately 0.43 (p<0.01)
• Self reported OLs less susceptible to peer influence
• Sociometric OLs no more or less susceptible
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Additional Thoughts about Leaders
1. Many ways to define and identify
2 M t f tl d N t k I t ti2. Most frequently used Network Intervention
3. Many studies of leaders and diffusion
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Implementation Issues
• Do you just turn leaders loose? How to t t i t tistructure interactions:
– Schedule 1‐1 between leaders & members
– Have leaders give formal presentations
– Have leaders call a meeting
– Allow leaders to decide how to promote changeAllow leaders to decide how to promote change
• Continuum of Passive to Active OL Involvement
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Strategy Tactic Operationalization
A Taxonomy of Network InterventionsValente, Science, 2012
Identification LeadersBridgesKey PlayersPeripheralsLow Thresholds
Degree, Closeness, etc.Mediators, BridgesPositive, Negative
Proportions, Counts
Segmentation GroupsPositions
Components, CliquesStructural Equivalence, Hierarchies
Induction WOMSnowballMatching
Random ExcitationRDS, OutreachLeaders 1st, Groups 1st
Alteration (Manipulation)
Deleting/Adding NodesDeleting/Adding LinksRewiring
VitalityOn Cohesion, OthersOn Network, On Behavior
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2. Segmentation
• Intervention is directed toward or includes a h l f lwhole group of people
• Segmentation interventions identify and expect a whole group to adopt the innovation at the same time
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2.A. Groups
• Sets of people/nodes that are densely t dconnected
• Groups can reinforce (or inhibit) the behavior change process
• Behavior change may be appropriate for groupsgroups
• There are many network methods used to find groups
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Newman-Girvan 6 Groups
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3.C. Match Leaders to Groups
• Rather than have leaders unattached, assign them to people who think they are g p p yleaders
• Leadership is local
• Emphasizes homophily between leaders and members
• Builds on naturally occurring networks• Builds on naturally occurring networks
• Leaders can be more effective if assigned to those who nominate them
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Network Influence is Proximal
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Sociogram based on ties Optimal leader/learner matching
Matching Leaders to GroupsMatching Leaders to Groups
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1(a) 1(b)
Graphical Displays of Intervention Choices
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Strategy Tactic Operationalization
A Taxonomy of Network Interventions
Identification LeadersBridgesKey PlayersPeripheralsLow Thresholds
Degree, Closeness, etc.Mediators, BridgesPositive, Negative
Proportions, Counts
Segmentation GroupsPositions
Components, CliquesStructural Equivalence, Hierarchies
Induction WOMSnowballMatching
Random ExcitationRDS, OutreachLeaders 1st, Groups 1st
Alteration (Manipulation)
Deleting/Adding NodesDeleting/Adding LinksRewiring
VitalityOn Cohesion, OthersOn Network, On Behavior 27
Degree Closeness
Keyplayers-Pos.Between
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Brokers
Keyplayers
ThresholdsBridges
Groups Positions
Hierarchies
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WOM Snow.
Outreach Matching
Vitality Node Addition
Link Deletion Link Addition
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Rewire SW Rewire Behavior
Graphical Displays of Intervention Choices
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Selecting a NI
• Availability and type of data
– Types of networks
– Existing network structure
• Behavioral characteristics
– Existing prevalence
– Perceived characteristics such as cultural– Perceived characteristics such as cultural compatibility; cost; trialability; etc.
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• There are several theoretical mechanisms that d i t i d b h i h
Linking Theory to Intervention Strategy
drive contagion and behavior change
• Evidence for a particular mechanisms suggests choice of intervention strategy or tactic
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Mechanism Tactic
PowerConflict
LeadersBridges
Influence Mechanisms Aligned with Interv. Choices
ConflictCohesionIsolationThresholds
BridgesKey PlayersPeripheralsLow Thresholds
Group IdentificationStructural Equivalence
GroupsPositions
Information diffusion WOMInformation diffusionHard to reach populationsClosureHomophily
WOMSnowballOutreachMatching
AttributesStructureStructure!!
Deleting/Adding NodesDeleting/Adding LinksRewiring
Leadership & Influence have 2 Dimensions
Trust
Low High
Expertise Low
High
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Discussion + Advice Nominations in the South Atlantic (Osteo.)
Prominence Nominations in the South Atlantic (Osteo.)
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