🍻 Your Friends Have More Friends Than You Do—Here's Why It Matters for Health
New research exploits the friendship paradox to use social contagion for good
The friendship paradox—the idea that “your friends have more friends than you do”—is usually just a fun thought-provoker. It refers to the fact that, mathematically speaking, people with many friends are more likely to be your friend than people with few friends. Thanks to this skew, when you average the number of friends your friends have and compare it to how many friends you have yourself, you’ll generally lose the popularity contest.
Earlier this year, one group of researchers decided to take the friendship paradox more seriously and put it to the test in the real world. How would information spread around a social network if you whispered it to a couple of random people vs whispered it to a couple of those random people’s friends?
🩺 Exploiting the friendship paradox to improve health
In a study published in May 2024, researchers mapped the face-to-face social networks of almost 25,000 people living across 176 villages in Honduras. One of their objectives was to improve people’s maternal and child health practices over the course of 22 months, since these are significant problem areas in low-income countries. According to CIA statistics, Honduras has a three times higher rate of infant mortality than the US.
The researchers used an educational intervention with in-person counseling focused on good practices for maternal, neonatal, and child health. Example practices included taking folic acid to reduce risks of birth defects, using birth plans, following ideal breastfeeding timelines, and adopting good hygiene practices for reducing childhood infections.
Random households in the study were selected to receive this information, but they were selected in one of two ways depending on whether they were assigned as an intervention or control group:
Control group: random households within each village were selected to receive educational counseling
Intervention group: random social connections of random households within each village were selected to receive educational counseling
The same numbers of people were “seeded” with the information in both groups. Surveys at the start and end of the two-year study tested village-wide knowledge and adoption of the health recommendations.
First, as a sanity check, the researchers found that education generally worked: villages showed significantly higher knowledge and behavioral adoption at the end of the study compared to the beginning.
More interestingly, the intervention group produced a significantly stronger effect than the control group. Telling people’s friends about an intervention was a more effective way of spreading health messages around a village than telling people directly.
For the vast majority of health outcomes (113 of 117 measures), giving health recommendations to a random sample of people in a village was almost as good as giving it to every single individual in that village. This is a huge efficiency advantage for health experts trying to spread information that improves health outcomes.
Educating a sample of second-order friends instead of first-order participants came with the largest efficiency boost. To achieve village-wide spread of a health message, you could tell 7.4% fewer people about it when targeting friends of people instead of people themselves. For the 33 health outcomes with the strongest direct benefits of education, this efficiency advantage increased to 12.31%.
Social contagion is a powerful tool for spreading important messages. Most people think of it in terms of memes, gossip, and viral videos, but we can piggyback on the same principles to spread more positive messages too. If you want to maximize the efficient spread of your message as a health practitioner or other subject matter expert, it’s particularly helpful to target people’s friends. This leverages the inherent biases of the friendship paradox to spread knowledge more widely through social connections.
🧠 What free subscribers missed last week: Last week’s Brainwave post for paid subscribers was a guide to saving democracy! A new megastudy has revealed the best available interventions for boosting pro-democracy sentiment and reducing partisan animosity.
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⭐️ Takeaway tips
#1. The friendship paradox is a practical principle
The friendship paradox is more than a surprising mathematical fact—it has very practical applications when trying to spread positive messages around communities. For example, if you’re a population health practitioner with limited time and resources, you should target your messages toward people’s friends. This boosts your social coverage since your message hits people who are likely to have larger networks of immediate connections.
#2. Start conversations about positive change
Positive messages with practical benefits can spread effectively. They might not spread as virally as the latest celeb gossip or funny social media video, but people want to share health and well-being facts with their loved ones. So start these kinds of conversations when you learn something new from a reliable source to spread a positive impact.
#3. Share simple, easy-to-adopt recommendations
In the research study above, easy-to-adopt principles and recommendations spread more easily around a community than more difficult principles. When deciding how to communicate your message, it’s important to simplify as much as possible without misrepresenting the original ideas. So boil down your message to the critical point you need someone to remember, and communicate it with confidence.
“The learning process is something you can incite, literally incite, like a riot. And then, just possibly, hopefully, it goes home, or on”
~ Audre Lorde