Some cognitive illusions, also called cognitive biases, can have a negative effect on reasoning and choice, as well as on emotional states. As a result, biased beliefs and decisions are mistaken, and people may experience negative feelings due to inaccurate expectations, notes Psychology Today. A cognitive bias is a tendency to judge or act based on insufficient information, overconfidence, attachment to past experience or self-interest.
One of the most prevailing cognitive illusions is called confirmation bias, which is the tendency of people to search for evidence that confirms their beliefs, instead of looking for evidence against them, as Psychology Today and About.com note. This bias negatively affects judgment because it makes people's beliefs resistant to contrary evidence, even if they are wrong.
Some cognitive illusions, such as the primacy effect, also called anchoring effect, negatively affect social interactions. This bias consists in a tendency to be overly influenced by the first piece of information received. It may have a negative effect on job interviews, since the interviewer's first impression of the candidate may not adequately reflect the candidate's value, as Science Magazine indicates.
Finally, a cognitive illusion that may have a negative effect on someone's choices and judgemnts is the optimism bias. People under this cognitive illusion underestimate the chances of negative events and overestimate the chances of positive events happening to them. This may lead to making risky or unhealthy decisions, such as smoking or not wearing a seat belt, as About.com notes.