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Recollection bias is the phenomenon whereby people, after observing a highly unexpected event, hold current risk beliefs about a similar event that are no higher than their recollection of their prior beliefs. This article explores recollection bias in relation to individuals’ perceptions of the risks of terrorism attacks. Over 60% of respondents in a national U.S. sample of over 900 adults believe that the risks of a future terrorist attack by either an airplane or in a public setting are no higher than they believed respectively before the 9/11 attack and the Boston Marathon bombing. Only one-fifth of respondents are free of any type of recollection bias. Recollection bias is negatively correlated with absolute levels of risk belief. Recollection bias—basically the belief that perceived risks have not increased—dampens support for a variety of anti-terrorism measures, controlling for the level of risk beliefs and demographic factors. Public attitudes influence policy. Thus, educating the public about risk is critical.


Viscusi, W. Kip, and Richard J. Zeckhauser. "Recollection Bias and Its Underpinnings: Lessons from Terrorism-Risk Assessments." HKS Faculty Research Working Paper Series RWP16-003, January 2016.