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<H1>Obesity, politics, STDs flow in social networks</H1>
<UL>
<LI class=cnnhiliteheader>Story Highlights
<LI>"Connected," a new book, describes social network research -- online
and off<BR>
<LI>People influence each other within three degrees of separation<BR>
<LI>Author: Online social networking is here to stay<BR>
<LI>Anthropologist: The expected size of social groups in humans should
be about 150<BR></LI></UL>
<DIV id=cnnSnapShotTimeStamp></DIV>
<DIV id=cnnSCByLine>By Elizabeth Landau<BR>CNN</DIV>
<P><B>(CNN)</B> -- Meet "network man." He has basic desires of his own,
but has many arbitrary preferences, such as in music or clothes, that have
been influenced by the people he knows.</P>
<P>Network man's likes and dislikes, in turn, affect the behavior of his
friends, and their friends, and their friends. For example, when he gets
into an obscure indie rock band, he shares an album with his friend, who
likes it so much that he recommends it to his cousin, who spreads the word
to her friends.</P>
<P>This is the view of human behavior put forth in "Connected," a new book
by Dr. Nicholas Christakis, professor at Harvard University, and James
Fowler, associate professor at the University of California, San
Diego.</P>
<P>Examining years of research of their own and from others, the authors
conclude that social networks, both offline and online, are crucial in
understanding everything from voting patterns to the spread of
disease.</P>
<P>People have profound influences on each other's behavior within three
degrees of separation, the authors find. That means that your friends,
your friends' friends, and your friends' friends' friends may all affect
your eating habits, voting preferences, happiness, and more. At the fourth
degree, however, the influence substantially weakens. <A
href="http://www.cnn.com/2008/HEALTH/12/05/happiness.social.network/index.html"
target=_blank>Read about their research on how happiness is
contagious</A></P>
<P>These are not small effects. "If a mutual friend becomes obese, it
nearly triples a person's risk of becoming obese," the book said. Even
geography doesn't matter; you're still at risk for gaining weight if a
friend 1,000 miles away gets bigger. <SPAN class=cnnembeddedmoslnk><IMG
border=0 alt=""
src="http://i2.cdn.turner.com/cnn/.element/img/2.0/mosaic/tabs/interactive.gif"
width=14 height=14><A
onclick="CNN_changeMosaicTab('otherTab1','other1.html',true);"
href="http://cnn.site.printthis.clickability.com/pt/cpt?action=cpt&title=Obesity%2C+politics%2C+STDs+flow+in+social+networks+-+CNN.com&expire=-1&urlID=412232440&fb=Y&url=http%3A%2F%2Fwww.cnn.com%2F2009%2FTECH%2F10%2F08%2Fsocial.networks.connected%2Findex.html&partnerID=211911#cnnSTCOther1">Listen
to James Fowler talk about social networks »</A></SPAN></P>
<P>Why is that? Obesity seems to spread in networks because of behavioral
imitation -- you copy what people close to you are doing -- and shared
expectations called "norms," the authors said. When you see people close
to you gaining weight, that makes you readjust your own idea of what is an
acceptable body size. <A
href="http://www.cnn.com/2009/HEALTH/07/10/attitudes.overweight/index.html"
target=_blank>Read more about how "overweight" is relative</A></P>
<P>Still, this does not mean you should get rid of your overweight
friends, Fowler said. In fact, the researchers re-examined the same data
set and found that people who dumped their friends who gained weight were
even more susceptible to obesity.</P>
<P>"On the one hand, yes, our work showed that if you keep your friend,
you are going to be susceptible to their bad behaviors," he said. "On the
other hand, time and again, what our work shows is that every friend makes
you healthier and happier." <SPAN class=cnnembeddedmoslnk><IMG border=0
alt=Video
src="http://i2.cdn.turner.com/cnn/.element/img/2.0/mosaic/tabs/video.gif"
width=16 height=14><A
onclick="CNN_changeMosaicTab('cnnVideoCmpnt','videos.html',true,'/');"
href="http://cnn.site.printthis.clickability.com/pt/cpt?action=cpt&title=Obesity%2C+politics%2C+STDs+flow+in+social+networks+-+CNN.com&expire=-1&urlID=412232440&fb=Y&url=http%3A%2F%2Fwww.cnn.com%2F2009%2FTECH%2F10%2F08%2Fsocial.networks.connected%2Findex.html&partnerID=211911#cnnSTCVideo">Watch
CNN's Elizabeth Landau talk about the book »</A></SPAN></P>
<P>Finding the hubs of social networks can be invaluable from a public
health point of view, the authors say. For example, instead of vaccinating
everyone in a population against a disease, it may be just as effective to
choose people at random and ask them to name their closest friends, then
vaccinate those friends.</P>
<P>The idea is that if someone names you as a friend, you are likely to be
more central to the network than a participant chosen at random. That
means you're probably less socially isolated, and more likely to come into
contact with a lot of people, than someone randomly selected.</P>
<P>"You can achieve the same level of protection for the population at
one-third the cost doing an intervention like this," Fowler said.</P>
<P>In fact, the authors hope to do a preliminary experiment monitoring the
spread of the novel H1N1 virus on a college campus, Fowler said. Using the
"friend" method for the vaccine against that virus, distributed for the
first time this week, would not be a bad idea, although it is still a new
concept that needs to be tested, Fowler said.</P>
<P>"What you are seeing is a lot of people who are experimenting with
these ideas in trials, and trying to figure out how can we use all of this
great new information about social networks to make everybody's life
better," he said.</P>
<P>Social networks were crucial to understanding how sexually transmitted
diseases broke out among teenagers in 1996 in Rockdale County, Georgia, a
quiet upper-middle-class suburb near Atlanta.</P>
<P>An investigation found that a collection of young girls, mostly under
16, had been having sex with various clusters of boys, the book said. This
epidemic of syphillis and other diseases stopped when the network changed,
the authors argue.</P>
<P>"They actually figured out a good intervention there, which was to
break apart this central group of girls that were essentially promoting
the spread of this norm of a heightened sexuality at a very young age,"
Fowler said. "By essentially quarantining them, the norm couldn't spread
anymore, and pretty soon they were able to get control of the
epidemic."</P>
<P>It turns out online social networks haven't necessarily expanded the
number of friends the average person has. Christakis and Fowler looked at
all of the <A class=cnninlinetopic
href="http://topics.cnn.com/topics/Facebook_Inc"
target=_blank>Facebook</A> pages of students at a particular unnamed
university and tried to figure out who was close friends with whom based
on "picture friends." Their reasoning: Two people who post and "tag" each
other in photos on Facebook are likely to be more socially close than
those who do not.</P>
<P>They found that, on average, students had between six and seven close
friends on Facebook, which is not far from sociologists' estimate that
most people have four to six close friends in real life.</P>
<P>Moreover, the expected size of social groups in humans, based on their
large brain size and the behavior of other primates, should be about 150,
according to British anthropologist Robin Dunbar. At the time "Connected"
was finalized, the average Facebook user had 110 registered friends on the
site, Fowler said.</P>
<P>The "Three Degrees Rule" may have evolved with the human species, the
authors argue. Having a social network in which influence spreads is
useful, as is knowing who is a potential ally or enemy based on friends'
associations. But humans evolved in small groups, not large collectives,
so during early human history there may not have been people who were four
degrees removed from anyone, they write.</P>
<P>The Iranian blogosphere, despite having a government that blocks access
to several Web sites, expresses many viewpoints on the Internet. In June,
Iranian citizens used Twitter to organize and protest against what they
viewed as an unfair election. <A
href="http://www.cnn.com/2009/TECH/06/23/why.retweet.twitter/index.html"
target=_blank>Read more about the power of retweeting</A></P>
<P>"In closed societies, the sheer value of being able to spread
information quickly is going to be the reason why social networks play
such a strong role," Fowler said.</P>
<P>An important caveat is that political organizing through social
networks, just like choosing financial investments, depends on what you
believe other people believe, he said. Bubbles in the stock market. for
example, are created when a lot of people believe a lot of other people
highly value a company's stock.</P>
<P>"The same thing happens with these protests," he said. "You're kind of
afraid to go out and do it yourself, but if you think that other people
are going to go show up, then you're more likely to show up yourself."</P>
<P>While social networking sites such as Friendster have risen and fallen,
online social networking in general is here to stay, Fowler said. He
likened it to the introduction of the telephone, which had its initial
skeptics too.</P>
<P class=cnninline>"This is just yet another way through which humans
exert their inherent natural tendency to try to connect to other people
that they care about," he
said.</P></TD></TR></TBODY></TABLE></DIV></FONT></DIV></BODY></HTML>