The University of California , San Diego, issued the following news release:

Acts of Kindness Spread Surprisingly Easily: Just a Few People Can Make
a Difference

For all those dismayed by scenes of looting in disaster-struck zones,
whether Haiti or Chile or elsewhere, take heart: Good acts — acts of
kindness, generosity and cooperation — spread just as easily as bad.
And it takes only a handful of individuals to really make a difference.

In a study published in the March 8 early online edition of the
Proceedings of the National Academy of Sciences, researchers from the
University of California, San Diego and Harvard provide the first
laboratory evidence that cooperative behavior is contagious and that it
spreads from person to person to person.

When people benefit from kindness they “pay it forward” by helping
others who were not originally involved, and this creates a cascade of
cooperation that influences dozens more in a social network.

The research was conducted by James Fowler, associate professor at UC
San Diego in the Department of Political Science and Calit2’s Center for
Wireless and Population Health Systems, and Nicholas Christakis of
Harvard, who is professor of sociology in the Faculty of Arts and
Sciences and professor of medicine and medical sociology at Harvard
Medical School. Fowler and Christakis are coauthors of the recently
published book “Connected: The Surprising Power of Our Social Networks
and How They Shape Our Lives.”

In the current study, Fowler and Christakis show that when one person
gives money to help others in a “public-goods game,” where people have
the opportunity to cooperate with each other, the recipients are more
likely to give their own money away to other people in future games.
This creates a domino effect in which one person’s generosity spreads
first to three people and then to the nine people that those three
people interact with in the future, and then to still other individuals
in subsequent waves of the experiment.

The effect persists, Fowler said: “You don’t go back to being your ‘old
selfish self.”’ As a result, the money a person gives in the first
round of the experiment is ultimately tripled by others who are
subsequently (directly or indirectly) influenced to give more. “The
network functions like a matching grant,” Christakis said.

“Though the multiplier in the real world may be higher or lower than
what we’ve found in the lab,” Fowler said, “personally it’s very
exciting to learn that kindness spreads to people I don’t know or have
never met. We have direct experience of giving and seeing people’s
immediate reactions, but we don’t typically see how our generosity
cascades through the social network to affect the lives of dozens or
maybe hundreds of other people.”

The study participants were strangers to each other and never played
twice with the same person, a study design that eliminates direct
reciprocity and reputation management as possible causes.

In previous work demonstrating the contagious spread of behaviors,
emotions and ideas — including obesity, happiness, smoking cessation
and loneliness — Fowler and Christakis examined social networks re-
created from the records of the Framingham Heart Study. But like all
observational studies, those findings could also have partially
reflected the fact that people were choosing to interact with people
like themselves or that people were exposed to the same environment. The
experimental method used here eliminates such factors.

The study is the first work to document experimentally Fowler and
Christakis’s earlier findings that social contagion travels in networks
up to three degrees of separation, and the first to corroborate evidence
from others’ observational studies on the spread of cooperation.

The contagious effect in the study was symmetric; uncooperative behavior
also spread, but there was nothing to suggest that it spread any more or
any less robustly than cooperative behavior, Fowler said.

From a scientific perspective, Fowler added, these findings suggest the
fascinating possibility that the process of contagion may have
contributed to the evolution of cooperation: Groups with altruists in
them will be more altruistic as a whole and more likely to survive than
selfish groups.

“Our work over the past few years, examining the function of human
social networks and their genetic origins, has led us to conclude that
there is a deep and fundamental connection between social networks and
goodness,” said Christakis. “The flow of good and desirable properties
like ideas, love and kindness is required for human social networks to
endure, and, in turn, networks are required for such properties to
spread. Humans form social networks because the benefits of a connected
life outweigh the costs.”

The research was funded by the National Institute on Aging, the John
Templeton Foundation, and a Pioneer Grant from the Robert Wood Johnson