While many individuals entertain an optimism bias, some people’s cognitions contain a pessimism bias. Pessimism bias is the overestimation of the probabilities and harmful effects of negative future events. This bias is most common in depressed individuals. It also becomes more common when asking about the future of the society in which a person lives. This bias is important to understand when considering public perception of government. It is also important to understand at a personal level, as a pessimism bias can make a person less successful at certain tasks. Interestingly, in certain settings, pessimism bias has been found to be more prevalent among women than men.
In a study by Mansour and Jouini, participants were asked to imagine that a coin was being flipped 10 times, and that they would win money if it landed on heads. They were then asked to predict how many times the coin would land on heads. The average guess was 3.9, significantly under the expected number of heads.