Chapter 4
This Hurts Me As Much As It Hurts You
Multiplexity
Multiplexity: the tendency to have several
kinds of relationships (or many kinds)
with the same person….
Your friend is also your co-worker and
your lover
Photo by Nick Slide
Photo by Barbara Doduk
Sexual Networks
Sexual networks are helpful in the study of social networks
because having sex with someone is a deliberate and
detectable type of social tie.
Not a Pretty Picture
In a wealthy suburb of Georgia there was an outbreak of
syphilis and other STDs among teenagers (and preteens!).
A large group of sexually active youth participating in “casual”
and group sex was discovered.
Photo by Shreyas, Flikr
Epidemic of Attitude
The STDs are a reflection of a
network process: the spread of
a norm among teenagers -- that
casual sex is acceptable
It was an epidemic of attitudes
with the symptoms being STDs
It’s acceptable
Photo by Jo Carter
The Network’s Role
At the core of the STD network were a few white, 15-year-old
girls who would have group sex with clusters of boys
This would connect many groups that would normally never be
linked (facilitating the flow of the STD)
Efforts to address the problem targeted and splintered the core,
changing the network
Group 1
Group 3
Core
Girls
Group 4
Group 2
High School Sex Networks
High School Sexual Networks follow 2 basic principles:
1. Homophily Principle: people resemble their partners (race,
grade, etc)
2. The Rule: “Don’t date your old partner’s current partner’s old
partner.’” CONFUSING?!
--Basically no-partner swapping with friends and exes
Photo by Jill Greenseth
Photo by Max Khokhlov
Photo by K Akagami
The Spread of Contagion
The more paths that connect you to other people in your
network, the more susceptible you are to what flows within it.
STDs and Race
Ed Laumann and his colleagues observed:
• Whites with many sexual partners tend to have sex with other whites
with lots of partners
• Whites with few partners have sex with whites with few partners
• Blacks with many partners have sex with blacks with BOTH few and
many partners
STDs are held in the “core” of active white partners but
spread to the periphery of the black population
The Obesity “Epidemic”
Your Friends’ Friends Can Make You Fat
Photos by Colin Rose and Sherrie G
The Obesity “Epidemic”
• 66% of Americans are overweight or obese
• From 1990 to 2000, the percentage of obese people in the
USA increased from 21% to 33%
Green Node: nonobese
Yellow Node= obese (size of circle is proportional to BMI)
1975
1990