--- title: "Kindness is contagious, up to three people away" url: https://magnanimo.us/daily/2026-10-28-kindness-is-contagious/ description: "A 2010 PNAS study found one person's generosity spread through strangers and roughly tripled. What it showed, its limits, and how to start a ripple." type: daily section: "Today's Kindness" published: 2026-10-28 updated: 2026-10-28 author: The Magnanimous Editors publisher: Magnanimous (https://magnanimo.us/) --- Today's Kindness · Science of giving # Kindness is contagious, up to three people away In a lab game among strangers, each act of generosity was copied down the line, reaching people up to three steps away. Selfishness spread too. By [The Magnanimous Editors](https://magnanimo.us/about/#editors) · Published Wednesday, October 28, 2026 · 3 min read · 3 linked sources If you give a little to someone you will never see again, does it stop there? A 2010 study by James Fowler of UC San Diego and Nicholas Christakis, then at Harvard, suggests it doesn't. Generosity in their study rippled outward to people who were never part of the original exchange, and by the end of the game each extra contribution had roughly tripled. ## A game among strangers The researchers didn't run new experiments. They went back to data from a well-known set of economics games and looked at it in a new way. In the paper, published in the [Proceedings of the National Academy of Sciences](https://pmc.ncbi.nlm.nih.gov/articles/PMC2851803/), they analyzed 240 people who played "a series of single-shot public goods games with strangers." In each round, players in groups of four got a small stake of money units and decided how much to keep and how much to put into a shared pot that benefited everyone. Then the groups were reshuffled, and nobody played with the same person twice. That reshuffling is what made the study clever. In real life, people who are kind tend to make friends with other kind people, so it's hard to tell whether behavior spreads or just clusters. Here, partners were assigned at random, and there was no chance of being paid back by the same person or building a reputation, as a [University of California, San Diego summary](https://www.sciencedaily.com/releases/2010/03/100308151049.htm) of the study explains. ## What spread, and how far People who had been in a group with generous players went on to give more in later rounds, to entirely new partners. The effect lasted for several rounds and, in the authors' words, "spreads up to three degrees of separation (from person to person to person to person)." Put together, they estimated that "each additional contribution a subject makes to the public good in the first period is tripled over the course of the experiment" by others who were influenced, directly or indirectly, to give more. "The network functions like a matching grant," Christakis told UC San Diego. Fowler described how long the effect lasted: "You don't go back to being your 'old selfish self.'" There is a catch, and the paper is upfront about it. The results "summarize the spread of both cooperative and uncooperative behavior." When someone gave less, that stinginess cascaded too. As the science writer Ed Yong noted in [National Geographic](https://www.nationalgeographic.com/science/article/pay-it-forward-cooperative-behaviour-spreads-through-a-group-but-so-does-cheating), the study really showed "that social contagion can be just as harmful as it is helpful." He also pointed out that the original players were Swiss university students, who probably knew they were playing with classmates, and people cooperate more readily within their own group. The authors are careful too. They say the tripling held "at least in a network of this particular, experimentally controlled structure," and Fowler said "the multiplier in the real world may be higher or lower than what we've found in the lab." So treat "kindness triples" as a striking lab result, not a law of nature. For more on what giving does for the giver, and which famous findings have and haven't held up, see our [science of giving](https://magnanimo.us/science-of-giving/) guide. ## Why it still matters Even with the caveats, the study points to something useful. What you do around other people sets a norm for what comes next, in both directions. A kind act seen and felt by others makes the next one more likely. A stingy one does the opposite. You can't control the whole chain, but you can choose which kind of link you are. ## Today's act **The act:** Start a ripple on purpose. Do one generous thing for someone today, and make it easy for them to pass it on. - Cover a coworker's coffee or lunch and say, "No need to pay me back. Get the next person." - In a group chat or team meeting, publicly thank someone for specific help. Others tend to follow a visible example. - If you're in a "pay it forward" line at a drive-through, keep it going rather than ending it. - Stuck for ideas? Spin our [kindness generator](https://magnanimo.us/kindness-generator/) or browse [random acts of kindness ideas](https://magnanimo.us/random-acts-of-kindness-ideas/). ## Sources 1. [Fowler, J.H. & Christakis, N.A. — Cooperative behavior cascades in human social networks, PNAS 107(12):5334–5338 (March 8, 2010)](https://pmc.ncbi.nlm.nih.gov/articles/PMC2851803/) 2. [ScienceDaily (from University of California, San Diego) — Acts of kindness spread surprisingly easily: just a few people can make a difference (March 10, 2010)](https://www.sciencedaily.com/releases/2010/03/100308151049.htm) 3. [National Geographic (Ed Yong) — Pay it forward? Cooperative behaviour spreads through a group, but so does cheating (March 8, 2010)](https://www.nationalgeographic.com/science/article/pay-it-forward-cooperative-behaviour-spreads-through-a-group-but-so-does-cheating) Today's act Do one visible, generous thing for someone today, then make it easy to pass on: tell them they don't owe you, just someone else. [How to do it](https://magnanimo.us/daily/2026-10-28-kindness-is-contagious/#todays-act) · [Draw another kindness](https://magnanimo.us/kindness-generator/) ## Go deeper Everyday generosity ### [The science of giving: what research says about generosity and happiness](https://magnanimo.us/science-of-giving/) The studies behind "giving makes you happy," what held up when researchers re-ran them, and how to use the findings without overselling them. 7 min read Everyday generosity ### [75 random acts of kindness ideas, from free to five dollars](https://magnanimo.us/random-acts-of-kindness-ideas/) Seventy-five small, specific kindnesses sorted by budget and setting, plus what research says about why they land harder than you expect. 7 min read Everyday generosity ### [Generosity at work: small habits that make a team better](https://magnanimo.us/generosity-at-work/) Workplace generosity is more than a charity drive. It's credit-sharing, mentoring, and covering for each other, and research suggests it helps teams. 4 min read ## More from Today's Kindness October 27 · History ### [Paul Newman bottled a holiday gift, then gave all the profits away](https://magnanimo.us/daily/2026-10-27-newmans-own/) A holiday gift in wine bottles became a food company that has given away every dollar of profit for more than 40 years. Today's act Turn something you make well into a small giving project: trade a batch for donations to a kids' charity you have checked out. October 26 · Everyday kindness ### [Giving blood: why the supply is always short, and what one hour of your time does](https://magnanimo.us/daily/2026-10-26-give-blood/) Blood can't be manufactured, red cells last 42 days and platelets five. That's why the need never ends, and why one hour of your time matters. Today's act Book a blood or platelet donation appointment for this week, or check if you're eligible if you've been turned away before. October 25 · Science of giving ### [The lost-wallet experiment: what 17,000 "lost" wallets in 40 countries revealed about honesty](https://magnanimo.us/daily/2026-10-25-lost-wallet-study/) Economists expected cash to tempt people. Instead, wallets with money came back more often in nearly every country. Even the experts guessed wrong. Today's act Return something today: a borrowed item, extra change a cashier gave you, or a lost thing you can get back to its owner. [Every entry in Today's Kindness →](https://magnanimo.us/daily/)