Extraordinarity bias is the individual and social tendency to value an object more than others in the same category as a result of an extraordinary property of that object that does not change the value in itself.

The extraordinarity does not have to be a fact, but can also be a belief. This makes the extraordinarity bias an instrument for those who want to change the perception of value of a certain object.

Examples are:

• the fact (or the believed fact) that a student is an orphan. This fact alone does not improve the quality of his / her studies, but he / she can get special treatment from teachers and his / her friends
• the fact (or the believed fact) that a house has been the living place of a certain famous person - this fact does not improve the quality of the house, but it can enhance the price of it