The (mis)measurement of the Dark Triad Dirty Dozen: Exploitation at the core of the scale

Background: The dark side of human character has been conceptualized in the Dark Triad Model: Machiavellianism, psychopathy, and narcissism. These three dark traits are often measured using single long instruments for each one of the traits. Nevertheless, there is a necessity of short and valid personality measures in psychological research. As an independent research group, we replicated the factor structure, convergent validity and item response for one of the most recent and widely used short measures to operationalize these malevolent traits, namely, Jonason’s Dark Triad Dirty Dozen. We aimed to expand the understanding of what the Dirty Dozen really captures because the mixed results on construct validity in previous research. Method: We used the largest sample to date to respond to the Dirty Dozen (N = 3,698). We firstly investigated the Dirty Dozen’s factor structure using Confirmatory Factor Analysis. Secondly, using sub-sample (n = 500) and correlation analyses, we investigated the Dirty Dozen dark traits convergent validity to Machiavellianism measured by the Mach-IV, psychopathy measured by Eysenck’s Personality Questionnaire Revised, narcissisms using the Narcissism Personality Inventory, and both neuroticism and extraversion from the Eysenck’s questionnaire. Finally, besides these Classic Test Theory analyses, we analyzed the responses for each Dirty Dozen item using Item Response Theory (IRT). Results: The results confirmed previous findings of a bi-factor model fit: one latent core dark trait, plus the three dark traits. An additional exploratory distribution analysis showed that all three Dirty Dozen traits had a striking bi-modal distribution, which might indicate unconcealed social undesirability with the items. The three Dirty Dozen traits did converge to, although not strongly, with the contiguous single Dark Triad scales (r between .41-.49). The probabilities of filling out steps on the Dirty Dozen narcissism-items were much higher than on the Dirty Dozen items for Machiavellianism and psychopathy. Overall, the Dirty Dozen instrument delivered the most predictive value with persons with average and high Dark Triad traits (Theta > -0.5). Moreover, the Dirty Dozen scale was better conceptualized as measured of a combined Machiavellianism-psychopathy factor, not narcissism, that can be replaced with item 4: ‘I tend to exploit others towards my own end’. Conclusion: The Dirty Dozen showed a consistent factor structure, a relatively convergent validity similar to that found in earlier studies. Narcissism measured using the Dirty Dozen, however, did not contribute with information to the core constitution of the Dirty Dozen construct. More importantly, the results imply a Single Item Dirty Dark Triad (SIDDT) measure of a manipulative and anti-social core as the content of the Dirty Dozen scale.