The researchers surveyed a national sample of Americans late in 2001, and then again a year later. Each time, they created experiences that accentuated one of the multiple emotions that the attacks evoked: fear, anger or sadness. One year out, the respondents' emotional reactions to the attacks continued to predict their perception of the risk of terrorism: Those who had their fear heightened were more pessimistic about the likelihood of future attacks and coping with the risk of terrorism, while those who had their anger heightened were more optimistic.
Overall, the respondents in 2002 believed future attacks were less likely than they had the previous year. However, when asked to recall their predictions from 2001, people remembered being more optimistic than they actually had been. That is, they remembered having seen a safer world than they actually had shortly after the attacks – a clear demonstration of hindsight bias. Reliving emotions colored their view of the past. Those who were made angrier remembered being more optimistic, whereas those made more fearful remembered being more pessimistic. Reliving emotions did not, however, reduce hindsight bias.
"The study raises two cautions for citizens thinking about terror or other hot topics. One is that they need to monitor their emotions. If they allow themselves to be angered, they may exaggerate the probability of success in anti-terror programs," said Baruch Fischhoff, the lead author and the Howard Heinz University Professor of Social and Decision Sciences and Engineering and Public Policy at Carnegie Mellon.
"The second caution is that they need to look for historical records when judging the wisdom of past decisions, rather than relying on their own memories," Fischhoff said.
The research also was conducted by Roxana Gonzalez and Jennifer Lerner, both in Carnegie Mellon's Department of Social and Decision Sciences, and Deborah Small, now at the Wharton School of Business at the University of Pennsylvania. The study was supported by the National Science Foundation, the National Institute of Mental Health and the American Psychological Association (Division 9).