The normalcy bias, or normality bias, refers to a mental state people enter when facing a disaster. It causes people to underestimate both the possibility of a disaster occurring and its possible effects. This often results in situations where people fail to adequately prepare for a disaster, and on a larger scale, the failure of governments to include the populace in its disaster preparations. The assumption that is made in the case of the normalcy bias is that since a disaster never has occurred then it never will occur. It also results in the inability of people to cope with a disaster once it occurs. People with a normalcy bias have difficulties reacting to something they have not experienced before. People also tend to interpret warnings in the most optimistic way possible, seizing on any ambiguities to infer a less serious situation.
Possible causes 
The normalcy bias may be caused in part by the way the brain processes new data. Research suggests that even when the brain is calm, it takes 8–10 seconds to process new information. Stress slows the process, and when the brain cannot find an acceptable response to a situation, it fixates on a single and sometimes default solution that may or may not be correct. An evolutionary reason for this response could be that paralysis gives an animal a better chance of surviving an attack; predators are less likely to eat prey that isn't struggling.
The normalcy bias often results in unnecessary deaths in disaster situations. The lack of preparation for disasters often leads to inadequate shelter, supplies, and evacuation plans. Even when all these things are in place, individuals with a normalcy bias often refuse to leave their homes. Studies have shown that more than 70% of people check with others before deciding to evacuate.
The normalcy bias also causes people to drastically underestimate the effects of the disaster. Therefore, they think that everything will be all right, while information from the radio, television, or neighbors gives them reason to believe there is a risk. This creates a cognitive dissonance that they then must work to eliminate. Some manage to eliminate it by refusing to believe new warnings coming in and refusing to evacuate (maintaining the normalcy bias), while others eliminate the dissonance by escaping the danger. The possibility that some may refuse to evacuate causes significant problems in disaster planning.
Not limited to, but most notably: The Nazi genocide of millions of Jews. Even after knowing friends and family were being taken against their will, the Jewish community still stayed put, and refused to believe something was "going on." Because of the extreme nature of the situation it is understandable why most would deny it.
New Orleans before Hurricane Katrina. Inadequate government and citizen preparation and the denial that the levees could fail were an example of the normalcy bias, as were the thousands of people who refused to evacuate.
Another example was during the September 11 attacks, many in the World Trade Center returned to their offices during the evacuation to turn off their computers and ultimately died when the towers collapsed.
The negative effects can be combated through the four stages of disaster response:
- preparation, including publicly acknowledging the possibility of disaster and forming contingency plans
- warning, including issuing clear, unambiguous, and frequent warnings and helping the public to understand and believe them
- impact, the stage at which the contingency plans take effect and emergency services, rescue teams, and disaster relief teams work in tandem
- aftermath, or reestablishing equilibrium after the fact by providing supplies and aid to those in need
See also 
- Doswell, Chuck. "Thoughts about Tornadoes and Camping Safety after the Iowa Tragedy on June 11, 2008." Flame.org. 26 July 2008 http://web.archive.org/web/20081120003313/http://www.flame.org/~cdoswell/Scout_tragedy/Scout_tragedy_2008.html.
- Oda, Katsuya. "Information Technology for Advancement of Evacuation." http://www.ysk.nilim.go.jp/kakubu/engan/engan/taigai/hapyoronbun/07-17.pdf.
- Ripley, Amanda. "How to Get Out Alive." Time 25 Apr. 2005. http://www.time.com/time/magazine/article/0,9171,1053663,00.html
- Valentine, Pamela V., and Thomas E. Smith. "Finding Something to Do: the Disaster Continuity Care Model." Brief Treatment and Crisis Intervention 2 (2002): 183-96.