Putting the “IRT” in “Dirty”: Item response theory analyses of the Dark Triad Dirty Dozen—An efficient measure of narcissism, psychopathy, and Machiavellianism

The Dark Triad Dirty Dozen is a new, concise personality inventory designed to measure individual differences in narcissism, psychopathy, and Machiavellianism in sub-clinical populations. To date, the psychometric work on this measure has used classical test theory to assess its validity, reliability, and structure. In two independent samples (N = 1014), we provide the first analyses of this measure using item response theory. In both samples, the Dark Triad Dirty Dozen efficiently recovered information and showed some evidence of differential scale functioning by sex, with a lower endorsement threshold for men compared to women. Results shed new light on the measurement of these “dark” personality traits.