Mass killings and school
shootings in the U.S. appear to be contagious, according to a team of
scientists from Arizona State University and Northeastern Illinois University.
Study author Sherry Towers,
research professor in the ASU Simon A. Levin Mathematical, Computational and
Modeling Sciences Center, explained, "The hallmark of contagion is
observing patterns of many events that are bunched in time, rather than
occurring randomly in time."
Her team examined databases on
past high-profile mass killings and school shootings in the U.S. and fit a
contagion model to the data to determine if these tragedies inspired similar
events in the near future.
They determined that mass
killings -- events with four or more deaths -- and school shootings create a
period of contagion that lasts an average of 13 days. Roughly 20 to 30 percent
of such tragedies appear to arise from contagion.
Their paper, "Contagion in
Mass Killings and School Shootings," appears in the July 2 edition of PLOS
ONE.
The analysis was inspired by
actual events in Towers' life.
"In January of 2014 I was
due to have a meeting with a group of researchers at Purdue University,"
she said. "That morning there was a tragic campus shooting and stabbing
incident that left one student dead. I realized that there had been three other
school shootings in the news in the week prior, and I wondered if it was just a
statistical fluke, or if somehow through news media those events were sometimes
planting unconscious ideation in vulnerable people for a short time after each
event."
The researchers noted that
previous studies have shown that suicide in youths can be contagious, where one
suicide in a school appears to spark the idea in other vulnerable youths to do
the same.
"It occurred to us that
mass killings and school shootings that attract attention in the national news
media can potentially do the same thing, but at a larger scale," Towers
said. "While we can never determine which particular shootings were
inspired by unconscious ideation, this analysis helps us understand aspects of
the complex dynamics that can underlie these events."
On average, mass killings
involving firearms occur approximately every two weeks in the U.S., and school
shootings occur on average monthly. The team found that the incidence of these
tragedies is significantly higher in states with a high prevalence of firearm
ownership.
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Story Source:
The above post is reprinted
from materials provided by Arizona State University. Note: Materials may be
edited for content and length.
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Journal Reference:
1. Sherry Towers, Andres Gomez-Lievano, Maryam Khan, Anuj
Mubayi, Carlos Castillo-Chavez. Contagion in Mass Killings and School
Shootings. PLOS ONE, 2015; 10 (7): e0117259 DOI: 10.1371/journal.pone.0117259
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Arizona State University.
"Mass killings, school shootings are contagious." ScienceDaily.
ScienceDaily, 2 July 2015.
<www.sciencedaily.com/releases/2015/07/150702151520.htm>.