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Study offers insight into social impacts of terror attacks

From the Feb. 7, 2005, Princeton Weekly Bulletin.

Breaking new ground in the study of terrorism, researchers at Princeton University and Hebrew University have found a link between terrorist attacks and traffic accidents in the days following the attacks.

The study, which examined an 18-month period in 2001-02 in Israel, showed that the number of fatal traffic accidents rose by 35 percent on the third day following terror attacks. After major attacks — ones that killed 10 or more people — the increase was 69 percent on the third day. While the researchers do not have immediate explanations for the connection, they see the study as an important first step in bringing rigorous techniques of social science to questions concerning terrorism and its effects.

“Once we know more about these short-term reactions, we can begin to understand how people are processing these events,” said Joshua Goldstein, a Princeton professor of sociology, who conducted the study with Guy Stecklov of Hebrew University in Jerusalem. Their work was published in the Oct. 5 issue of the Proceedings of the National Academy of Sciences.

In their paper, Stecklov and Goldstein note that other researchers, including a panel convened recently by the National Academy of Sciences, have called for better quality data and careful studies of the effects of terrorism. “Terror attacks are thought to have profound, society-wide consequences that extend far beyond the immediate victims of the violence, but until now there has been little empirical evidence of population-wide effects,” the authors wrote.

Other work at Princeton is pushing in a similar direction. Alan Krueger, professor of economics, has written articles advocating far more rigorous methods of reporting data about the incidence of terror attacks. In the September/October issue of Foreign Affairs, Krueger and David Laitin of Stanford University wrote that “statistics on terrorist attacks are becoming as important as the unemployment rate or the [gross domestic product]. Yet the terrorism reports produced by the U.S. government do not have nearly as much credibility as its economic statistics, because there are no safeguards to ensure that the data are as accurate as possible and free from political manipulation.”

Krueger also has published papers about the origins of terrorism and argued against the common view that there is a direct connection between poverty and terrorism. Instead, he contends that terrorism originates in countries that suffer from political oppression. Economic status has to do with the target, rather than the origin of attacks, according to Krueger: Countries with strong economies are more likely to be the targets of terrorism.

In their study of terror attacks and traffic accidents, Stecklov and Goldstein took advantage of the clearly defined records of terrorist attacks in Israel as well as that country’s traffic statistics. They carefully adjusted the accident statistics to account for changes in traffic volume in the days being studied and for independent effects such as the fact that both accident rates and terror attacks are more likely on Sundays, the beginning of the Israeli week. After looking at 63 terror attacks during the study period, the researchers were surprised to find statistically significant effects, with very little chance that they resulted from random coincidence.

In addition to the increased fatalities on the third day after attacks, the researchers found a decline in minor accidents the day after the attacks. They speculated that this may have resulted from reduced reporting of accidents rather than people driving more carefully. They also noted that, while the number of traffic fatalities increased, there was no corresponding rise in the number of accidents that were serious but not fatal.

At this point, the results suggest more questions than answers, said Goldstein. “One puzzle is why we see the reaction to terror on day three and no other day. Another is why there was an increase in fatal accidents but not serious accidents.”

One hypothesis that the researchers raise in the paper is that some of the fatal accidents are suicides, an idea supported by other studies on imitative suicide, which find increases in traffic fatalities and suicides three days after well-publicized suicides and murders. However, they note it also is possible that the increase in fatalities results from some other reaction to violence and stress.

The key advance, said Goldstein, in addition to the detection of particular statistical effects is that the traffic data may prove to be a society-wide measure that can be used to study the social effects of terror over time and perhaps across societies.

The research also suggests a way to bridge the society-wide effects that sociologists study and the individual-level mental reactions that psychologists examine. “This is one of the first studies that leads you to think about what the psychological mechanism is, because the effect is specific enough,” said Goldstein. “It appears, it disappears. It appears bigger with bigger attacks. Those are all details you can think about.”

Eldar Shafir, a Princeton professor of psychology who studies how people make decisions in situations of conflict and uncertainty, agreed that the study is intriguing. “There obviously is something happening at the individual level that is of interest to people like me and the question is: What?” said Shafir. “It’s fascinating work. Psychologists ought to pay attention.”

Goldstein, whose primary area of research is in social demography, said he and Stecklov plan to update their study soon to see if the effect of terror is getting stronger or weaker with time. They also are considering a study of the societal response to the 9/11 attacks in the United States. In the meantime, he has begun receiving responses from other researchers who have seen similar three-day effects in other contexts.

“Perhaps measures of traffic accidents will shed light on other societal events, or, conversely, studies of other phenomena may help explain the connection we are seeing between accidents and terror attacks,” said Goldstein. “It has been rewarding that people in entirely different specialties are reading this paper and sending ideas.”

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