Testing construct independence in the Short Dark Triad using Item Response Theory

•Item Response Theory was used to establish SD3 item parameter estimates.•Machiavellianism items are more easily endorsed than psychopathy items.•Psychopathy and Machiavellianism could be modelled together in one factor.•Psychopathy and narcissism could be modelled together in one factor.•Narcissism and Machiavellianism could not be modelled together in one factor.

The Dark Triad (i.e., Machiavellianism, narcissism and psychopathy) is a popular construct for describing socially aversive personality traits. In recent years, the Short Dark Triad (SD3; Jones & Paulhus, 2014) has become a popular measure for assessing the Dark Triad constructs. However, recent research has called the supposed dissimilarity between the Dark Triad constructs into question. In particular, theoretical and empirical evidence suggests that a distinction between Machiavellianism and psychopathy may not be tenable. In order to investigate this issue further, we analyzed the SD3 in a large sample (N = 1983) using Item Response Theory. We establish item response parameter estimates for each Dark Triad construct and further test whether the Dark Triad constructs can be modelled together. Results show that Machiavellianism and narcissism could not be modelled together, but the combinations Machiavellianism and psychopathy, and narcissism and psychopathy, yielded acceptable model fit. The implications of these results are discussed in terms of how the Dark Triad constructs may be interpreted and studied in the future.