This refers to the idea that the human brain is designed by nature to be paranoid as a defence mechanism to protect itself from possible dangers that could be fatal to its chances of survival. While paranoia can lead the brain to commit a lot of false positive errors, it can, however, help human beings avoid a number of false negative errors which could turn out to be extremely costly as well. This is similar to the way a smoke detector is designed by engineers, who want the device to never miss an actual fire even if such a design causes the device to raise a number of false alarms. The term was coined by American physician Randolph M. Nesse in a 2006 paper.
