On the Usefulness of Item Bias Analysis to Personality Psychology

A form of item bias known as Differential Item Functioning (DIF) occurs when two individuals with the same trait levels but different group membership do not have the same probability of endorsing an item in the keyed direction. The detection of DIF using Item Response Theory (IRT) arose in the cognitive testing domain, so the phenomenon is almost invariably perceived as undesirable. With the extension of IRT procedures to substantive areas of psychology, it is argued that DIF-prone items can afford valuable insights into the nature of the construct under study, especially where group differences are important. An example is presented using responses from 568 students completing a popular measure of Openness to Experience.