A Randomized Trial: Social Network Targeting to Maximize Population Behavior Change

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Journal Club Webinar, June 2015

A Randomized Trial:

Social Network Targeting to Maximize

Population Behavior Change

Tom Davis

Chief Program Officer Feed the Children

Ben Tidwell

Former Health Program Manager Samaritan’s Purse, Iraq Julie Tanaka

Senior International Nutrition Advisor Samaritan’s Purse

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• Article was published May 5, 2015

in

The Lancet

• Groundbreaking

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Randomized control trial

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Insight into dynamics of

face-to-face social networks, as opposed

to online social networks

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Nomination targeting has never

been tested experimentally as a

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"We humans construct elaborate social networks in which we live out our lives. If scientists can

understand the structure and function of these social networks, we can take advantage of this understanding to turbo-charge behavioral

interventions so that whole groups of people

change their behavior for the better, and not just isolated individuals,"

--Nicholas Christakis, author, professor of sociology, ecology & evolutionary biology,

biomedical engineering, and medicine at Yale.

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• Information and Behavior can spread through interpersonal ties

• Targeting Influential Individuals—harnessing the distributive properties of social networks

• Objectives of the Study:

- Primary Outcome: see which targeting method resulted in the greatest uptake and diffusion of the health interventions.

- Secondary Outcome: see which targeting method resulted in greater diffusion of knowledge on the health interventions.

• Goal: maximized population-level behavior change

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• Between Aug 4 - 14, 2012, 32 villages in rural Honduras (25–541 participants each; total

study population of 5773) received public health interventions

• Blocked villages on the basis of:

- network size, socioeconomic status, and baseline rates of water purification

• Focused on delivery of two public health interventions:

- chlorine for water purification and

multivitamins for micronutrient deficiencies

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• Randomized villages selected, separately for each intervention, to one of three targeting methods:

1. Nominated friends of random villagers (n=9)

 “Nomination targeting” or “network targeting” or “nominated friends targeting” or “friendship

nomination technique”

 friendship paradox of social networks

2. Villagers with the most social ties (n=9);

 Indegree targeting

3. Randomly selected villagers (n=9 villages for each intervention);

 Random targeting

• Introduced the interventions to 5% samples in each village

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Journal Club Webinar, June 2015 • Each targeted individual received:

- A health product

- Instructions for use

- An educational component

- Supplementary information about the intervention not generally known at baseline and asked them to relay this information to others

 Allowed them to track the diffusion of knowledge

- 4 tickets to distribute to friends or family—outside the household but within the village

- Targets were asked to instruct the villagers to whom they gave tickets about the correct usage and benefits of the product

• Tickets were uniquely identified. Ticket redemption allowed the study to track the rate and extent of product diffusion through the village networks

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• Supplemented with an extensive follow-up survey 4-6 weeks after the intervention

• Villagers were asked:

- whether they redeemed a ticket

- their use of the products

- their attitudes concerning the products’ utility and effectiveness

- a series of factual question about their correct usage and benefits (knowledge scores were derived)

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• Primary Outcomes--the proportions of available products (multi-vitamin or chlorine) redeemed by the entire population under each targeting method (product adoption)

• Secondary Outcomes—proportions of villagers under each targeting method attaining high

knowledge scores (knowledge diffusion)

- Composite 0-10 scores, percentage of respondents in each

targeting method achieving scores in the top quartile

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• In nomination-targeted villages, 951 (74·3%) of 1280 available

multivitamin tickets were redeemed

• 744 (61·0%) of 1220 in indegree-targeted villages

• 940 (66·2%) of 1420 in random targeting villages

• All pairwise differences in

redemption rates were significant (p<0·01) after correction for

multiple comparisons

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• Targeting nominated friends increased adoption of the nutritional intervention by 12·2% compared with random targeting (95% CI 6·9–17·9).

- An 8.1% point increase in product adoption

• Positive effect of nomination targeting on the uptake of the multivitamin intervention

• For the Chlorine intervention, final ticket redemption rates were statistically indistinguishable across targeting methods

• Targeting the individuals with the most social ties (indegree) produced no greater adoption of either intervention,

compared with random targeting.

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Multivitamin Intervention:

• 30.8% of untargeted ticket recipients, who were not part of any of the three aforementioned sampling groups, attained high knowledge scores in nomination targeted villages

• 27.6% in both indegree and random targeted villages

• Positive and statistically significant effect of nomination targeting (compared with random targeting) on the

attainment of high multivitamin knowledge scores

Chlorine Intervention:

• No significant effect of targeting method on knowledge scores

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• Social network mapping identified the most

socially connected people

• The most socially connected people are not

necessarily the key influencers in a network

• Theory: popular individuals are overly

clustered amongst themselves

• Certain

public health interventions work

best when key influencers in a face-to-face

social network are exposed to the program.

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• Can exploit the intrinsic properties of human social networks through the nomination targeting

• Targeting nominated friends is more scaleable and less resource intensive than social network

mapping

- Do not have to increase the number of

individuals targeted or the resources used

• Introduction of a SBC program to the nominated friends of random individuals can enhance its diffusion—boost adoption and reach of certain programs

• Nomination targeting may work for: immunizations, anti-malarial bednets, antenatal care visits,

exclusive breastfeeding, handwashing, etc.

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• David A Kim, Alison R Hwong, Derek

Stafford, D Alex Hughes, A James O’Malley,

James H Fowler, Nicholas A Christakis

• Trial is registered with ClinicalTrials.gov,

number NCT01672580.

• www.thelancet.com

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Published online May 5, 2015

http://dx.doi.org/10.1016/S0140-6736(15)60095-2

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