Gender Differences or Gender Bias? Examination of the Assessment of Sadistic Personality Using Item Response Theory and Differential Item Functioning

Sadism, defined by the infliction of pain and suffering on others for pleasure or subjugation, has recently garnered substantial attention in the psychological research literature. The Assessment of Sadistic Personality (ASP) was developed to measure levels of everyday sadism and has been shown to possess excellent reliability and validity using classical test theory methods. However, it is not known how well ASP items discriminate between respondents of different trait levels, or which Likert categories are endorsed by persons of various trait levels. Additionally, individual items should be evaluated to ensure that men and women of similar levels of sadism have an equal probability of response endorsement. The purpose of this research was to apply item response theory (IRT) and differential item functioning (DIF) to investigate item properties of the ASP across its three translations: English, Polish, and Italian. Overall, the results of the IRT analysis showed that with the exception of Item 9, the ASP demonstrated sound item properties. The DIF rate analyses identified two items from each questionnaire that were of practical significance across gender. Implications of these results are discussed.