Bacterial and viral illnessesspread in human communities. But what
about physical fitness, happiness, sadness and habits such as smoking,
drinking and eating too much?Nicholas Christakis,
a physician and sociologist and James Fowler,
a political scientist, have uncovered powerful evidence that many kinds
of behavior are contagious. They discovered an informational gold mine
in records of the famous Framingham Heart Study
which has followed more than 15,000 people from Framingham,
Massachusetts and their descendants since it was founded by the National
heart Institute in 1948. Every four years participants got a compete
physical, in which dozens of health measurements were collected--weight,
heart rate, blood levels and illnesses. Participants were also asked to
name their family members, their doctor, place of employment and
residence, and friends who might be able to locate them if researchers
needed help finding them later. With years of careful work sifting
through data, Christakis and Fowler were able to create a map showing
how 5,124 people were connected in a web of 53,228 ties among friends,
family members and work colleagues.
When they summarized their findings on obesity in a July 2007 article in the New England Journal of Medicine,
it was the first time a prestigious a journal had published on the subject of social networks and health.
A New York Times Magazine
story,"Are Your Friends Making You Fat"
, by Clive Thompson, describes the growing impact of their work and an
increasing recognition that all kinds of behavior-healthy and
unhealthy-may very well travel through networks in surprising ways.
Counter intuitively, we don't just influence those in our immediate
environs, the researchers say, but those at a distance in a web that
stretches farther than we know. As Christakis and Fowler write in their
new book, Connected: The Surprising Power of Our Social Networks and How They Shape Our Lives:
"You may not know him personally, but you friend's husband's co-workers
can make you fat. And your sister's boyfriend can make you thin." If
you think that sounds implausible, read their work. When you think about
mirror neurons, subconscious social cues and subtle shifts in
perception about what's normal and acceptable, it begins to make sense.
It also suggests that health is a communal endeavor, and that public
health policies need to reach beyond the individual.
note that even when networks maps show in clusters of obesity, smoking
or happiness, connectivity doesn't prove contagion as the cause. Factors
of a shared environment and the tendency of people to gravitate toward
those who are like them could account for that. But Christakis and
Fowler found that the nature of the relationship influences the
likelihood of spread. For instance, with obesity, spouses of different
sex didn't have much effect on each other. But if a male in the
Framingham study had a male friend who got fat, his chances of obesity
doubled. If his wife got fat, his risk only went up 37 percent. It
turns out that adults "catch" obesity when someone of their own sex
gains weight--probably because people regard their own bodies in
comparison with members of their own sex, and notions of acceptability
are subtly influenced in that context. The Times
out that the more we learn about social networks, the more issues
arise: To what extent can we choose or influence our own networks? Is
our level of connectedness somehow innate? What do networks say about
individual responsibility? Do we have free will?Philosophers and
scientists will spend years on these questions.